Organic Vegetable Production - New York Cooperative Extension

2,018 views
1,924 views

Published on

Organic Vegetable Production - New York Cooperative Extension

Published in: Education
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
2,018
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
25
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Organic Vegetable Production - New York Cooperative Extension

  1. 1. Fair Use of this PDF file of Organic Vegetable Production, NRAES-165 Proceedings from NYS Agricultural Experiment Station, January 14–16, 2003 Published by NRAES, March 2004This PDF file is for viewing only. If a paper copy is needed, we encourage you to purchase acopy as described below.Be aware that practices, recommendations, and economic data may have changed sincethis book was published.Text can be copied. The book, authors, and NRAES should be acknowledged. Here is a sampleacknowledgement:----From Organic Vegetable Production, NRAES-165, published by NRAES (2004).----No use of the PDF should diminish the marketability of the printed version. This PDF shouldnot be used to make copies of the book for sale or distribution.If you have questions about fair use of this PDF, contact NRAES. Purchasing the BookYou can purchase printed copies on NRAES’ secure web site, www.nraes.org, or by calling (607)255-7654. Quantity discounts are available.NRAESPO Box 4557Ithaca, NY 14852-4557Phone: (607) 255-7654Fax: (607) 254-8770Email: nraes@cornell.eduWeb: www.nraes.orgMore information on NRAES is included at the end of this PDF.
  2. 2. AcknowledgmentsPartial FundingThe Organic Vegetable Production workshop was partially funded by the Northeast Region SustainableAgriculture Research and Education (SARE) program, which is administered by the Cooperative StateResearch Education and Extension Service and the USDA.About the Workshop and ProceedingsThe workshop was coordinated by Abby Seaman, Area Extension Educator, New York State IntegratedPest Management Program, Cornell Cooperative Extension. The proceedings was edited by Abby Sea-man.These meetings were intended for commercial vegetable growers who are currently growing organicallyor want to learn more about organic practices, as well as beginners contemplating organic vegetableproduction. University and farmer speakers covered the basics of soil and nutrient management, weedmanagement, and insect and disease management.Thanks to SpeakersThe workshop coordinator and NRAES would like to thank the speakers for their diligence in submit-ting their papers for these proceedings.DisclaimerTo simplify information, trade names have been used in this publication. No endorsement of namedproducts is intended, nor is criticism implied of similar products that are not mentioned.Proceedings ProductionJeffrey S. Popow, NRAES managing editor, designed the proceedings and managed the proceedingsproject.About NRAESSee the inside back cover for information about NRAES, including contact information and a list ofNRAES member universities.
  3. 3. Cooperative Extension NRAES–165 Organic Vegetable Production Proceedings from a Three-Day Series of Meetings Jordan Hall Auditorium New York State Agricultural Experiment Station Geneva, New York January 14–16, 2003 Natural Resource, Agriculture, and Engineering Service (NRAES) Cooperative Extension PO Box 4557 Ithaca, New York 14852-4557
  4. 4. NRAES–165 March 2004 © 2004 by NRAES (Natural Resource, Agriculture, and Engineering Service). All rights reserved. Inquiries invited. ISBN-13: 978-0-935817-96-6Requests to reprint parts of this book should be sent to NRAES. In your request, please state whichparts of the book you would like to reprint and describe how you intend to use the reprinted material.Contact NRAES if you have any questions. Natural Resource, Agriculture, and Engineering Service (NRAES) Cooperative Extension PO Box 4557 Ithaca, New York 14852-4557 Phone: (607) 255-7654 Fax: (607) 254-8770 E-mail: nraes@cornell.edu Web site: www.nraes.orgii
  5. 5. ContentsAbout the Speakers................................................................................................................... viSoil and Nutrient ManagementSoil Life..................................................................................................................................... 3 Janice Thies Department of Crop and Soil Sciences Cornell UniversityInterpreting Soil Test Results and Estimating Nutrient Availability.......................................... 6 John Howell UMass Extension University of MassachusettsTillage Practices for Maintaining Soil Quality........................................................................ 16 Harold van Es Department of Crop and Soil Sciences Cornell UniversityCompost and Cover Crops for Organic Vegetable Growers.................................................... 21 Brian Caldwell Northeast Organic Farming Association of New YorkSoil and Nutrient Management Practices on Upingill Farm.................................................... 24 Cliff Hatch Upingill Farm Gill, MassachusettsSoil and Nutrient Management Practices on Roxbury Farm................................................... 34 Jean-Paul Courtens Roxbury Farm Kinderhook, New YorkFertility Management at Roxbury Farm.................................................................................. 45 Jean-Paul Courtens Roxbury Farm Kinderhook, New York iii
  6. 6. ContentsWeed ManagementUnderstanding Weed Biology.................................................................................................. 59 Charles L. Mohler Crop and Soil Sciences Cornell UniversityWeed Management on Organic Vegetable Farms.................................................................... 76 Vern Grubinger University of Vermont ExtensionHow to Get 99% Weed Control without Chemicals................................................................ 83 Brian Caldwell Northeast Organic Farming Association of New YorkMulching for Weed Control and Organic Matter..................................................................... 87 Paul Arnold Pleasant Valley Farm Argyle, New YorkBio-Extensive Approach to Market Gardening..................................................................... 100 . Anne and Eric Nordell Beech Grove Farm Beech Grove, PennsylvaniaA Few Long Furrows on Horsedrawn Tillage....................................................................... 105 . Eric and Anne Nordell Beech Grove Farm Beech Grove, Pennsylvaniaiv
  7. 7. ContentsInsect and Disease ManagementImpacts of Soil Quality on Disease and Insect Resistance in Plants..................................... 113 Anusuya Rangarajan Dept. of Horticulture Cornell UniversityDisease Management Strategies: Cultural Practices.............................................................. 120 Helene R. Dillard Department of Plant Pathology New York State Agricultural Experiment Station; Geneva, New York Cornell Cooperative ExtensionCultural Practices for Disease Management.......................................................................... 123 Curtis Petzoldt Integrated Pest Management Program New York State Agricultural Experiment Station; Geneva, New YorkIdentifying and Encouraging Beneficial Insects.................................................................... 128 Michael P. Hoffmann NYS IPM Program and Department of Entomology Cornell UniversityInsect Management:Managing Beneficial Habitats, Using Organic Insecticides.................................................. 136 Ruth Hazzard Dept. of Entomology University of Massachusetts ExtensionPest Management on Applefield Farm................................................................................... 142 Steve Mong Applefield Farm Stow, MassachusettsPest Management from a Farmer’s Perspective.................................................................... 152 . David Marchant River Berry Farm Fairfax, Vermont v
  8. 8. About the SpeakersPaul Arnold and Sandy Arnold have been farming at David Marchant and Jane Sorensen operate River BerryPleasant Valley Farm for 12 years and raise about 8 acres of Farm alongside the LaMoille River in the Champlain Basinorganic fruits and vegetables on their 60 acres in Washington of Vermont. They grow approximately 40 acres of certifiedCounty, New York, with two children. Their living is made organic vegetables, 4 acres of IPM managed strawberries,by selling all of their produce at 4 area farmers’ markets. and 15 acres of grain. The vegetables are marketed out of state through the Deep Root Organic Cooperative, and lo-Brian Caldwell is the education director for NOFA-NY. cally through stores and farmers markets.He is also an experienced grower of organic vegetables andfruit at Hemlock Grove Farm in West Danby, New York. Chuck Mohler is a senior research associate in the depart- ment of Crop and Soil Sciences. Most of his work hasJean-Paul Courtens, the founding farmer of Roxbury Farm, focused on the effects of tillage, cultivation, and crop residuewas born and raised in the Netherlands, where he studied on the population dynamics of annual weeds. He is a co-biodynamic agriculture. Roxbury Farm grows vegetables, author of the book Ecological Management of Agriculturalherbs, melons, and strawberries using biodynamic practices Weeds.on 148 acres in Kinderhook, New York for a CSA of 650families in four communities. Steve Mong, his wife Kirsten, and brother Ray have operated Applefield Farm for 20 years. It is a 25-acre farm with 20,000Helene Dillard has conducted basic and applied research square feet in greenhouses, which are used for bedding plant,on the biology, ecology, and management of fungal and hanging basket, annual, and perennial production. Steve hasbacterial pathogens of vegetables at the New York State been an active cooperator in University of MassachusettsAgricultural Experiment Station in Geneva, New York since pest management trials.1984. She has been the director of Cornell CooperativeExtension, a primary outreach unit of Cornell University, Anne and Eric Nordell grow vegetables, herbs, andsince 2002. strawberries on 6.5 acres in Trout Run, Pennsylvania. They have developed an elegant whole farm approach to nutrientVern Grubinger is the director of the Center for Sustainable and weed management. Their produce is marketed throughAgriculture at the University of Vermont. He has extensive grocery stores, restaurants, and farmers’ markets.experience in many aspects of organic and sustainable veg-etable and small fruit production. He is the author of the book Curt Petzoldt is the Assistant Director and Vegetable Coor-Sustainable Vegetable Production from Startup to Market. dinator at the New York State IPM Program. For the past ten years he has conducted multidisciplinary trials comparingCliff Hatch has over 20 years of experience in organic the environmental and economic attributes of conventional,production. He grows a variety of vegetables, strawberries, IPM, and organic production systems at the research farmand grains at Upingill Farm in Gill, Massachusetts. and on growers’ farms.Ruth Hazzard is team leader for the Vegetable Program Anu Rangarajan is an associate professor in the Departmentand also coordinates the Integrated Crop and Pest Manage- of Horticulture at Cornell and statewide specialist for Freshment Project for vegetables. Her research has focused on Market Vegetable Production. Her research program focusesinsect and disease management in brassicas, sweet corn, on specialty crop variety trials, and developing productiontomato, and peppers. Currently she is involved with studies systems that minimize chemical fertilizer and pesticideon biointensive insect management in brassicas, cucurbits, inputs and maximize crop nutritive value.and sweet corn. Janice Thies is an associate professor of soil biology whoMike Hoffmann is the director of the New York State IPM joined the Cornell faculty in 2000. Janice’s research programProgram and a professor in the Department of Entomology focuses on three main areas: soil microbial population genet-in Ithaca. His research and extension program focuses on ics, the influence of management practices on soil microbialalternative insect management strategies. community structure, and the development of biofertilisers and biopesticides for use in low-input agriculture.John Howell recently retired as Extension VegetableSpecialist at the University of Massachusetts. His areas Harold van Es joined the Cornell faculty in 1988. Hisof special interest include vegetable production systems, research, extension, and teaching programs address thenutrient and soil management, greenhouse tomato produc- management of soil and water resources for sustainabletion, trickle irrigation and fertigation, and water garden agricultural production and environmental protection. Heconstruction and maintenance. is a co-author of the book Building Soils for Better Crops.vi
  9. 9. This page is from Organic Vegetable Production, NRAES-165. To purchase the book,visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information. Soil and NutrientManagement
  10. 10. This page is from Organic Vegetable Production, NRAES-165. To purchase the book,visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.
  11. 11. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information. Soil Life Janice Thies Associate Professor Department of Crop and Soil Sciences Cornell UniversityThe diverse and numerous creatures living in the soil Soil arthropodsprovide a variety of benefits to crops and but also havepotential detriments. The benefits include the decom-position of organic matter, nutrient cycling and release, There are four major groups of soil arthropods. Preda-nitrogen fixation and mycorrhizal relationships, disease tors such as ants, ground beetles, and spiders help con-suppression, and soil structure improvement. Potential trol crop pests. Another group including dung beetles,detriments include immobilization of nutrients and the mites, and sow bugs shred organic matter. Fungal feed-ability to cause plant and animal disease. ers such as springtails and turtle mites release nutrients tied up in fungal biomass. And herbivores such as mole crickets and symphylans can cause crop damage bySoil food web feeding on roots. Functional roles of arthropods include shredding of organic matter which stimulates microbial activity, mixing microbes with organic matter, miner-The complex network interactions that occur between alizing plant nutrients, increasing aggregation of soil,organisms in the soil is sometimes described as the burrowing, which increases soil channels, preying onsoil food web. Plants are the foundation of the soil other arthropods, and feeding on plants.food web, capturing energy from the sun throughphotosynthesis and providing the organic matter thatother organisms work on. Decomposers such as bac- Earthwormsteria and fungi work on the material produced by theplants releasing nutrients in a form that is usable byplants. Small arthropods, nematodes, protozoa, and Earthworms are another important group soil or-earthworms shred and consume the organic matter ganisms, considered by some to be soil ecosystemproduced by the plants, making it more available to the engineers. They move tremendous amounts of soilbacteria and fungi, and also consume the bacteria and through their guts as they burrow. In the process, theyfungi themselves, releasing plant-available nutrients. stimulate microbial activity, mix and aggregate soil,Larger arthropods and small mammals then consume increase soil infiltration rate and water holding capac-the smaller creatures releasing more nutrients. ity, create channels for plant roots, and bury and shred plant residues.Soil and Nutrient Management 3
  12. 12. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.Nematodes mycorrhizae, such as many ectomycorrhizae, are good saprophytes, and function independent of plants. The ectomycorrhizae associate primarily with trees.Soil nematodes are very small (300-500 µm), ubiq- These associations consist of a sheath surroundinguitous and abundant in soils. They depend on water the root and limited intercellular penetration betweenfilms on soil particles to swim and survive. They have cells in the root cortex. The endomycorrhizae associ-a range of feeding strategies including plant parasites, ate primarily with crop plants. In this symbiosis, thebacterial and fungal feeders, predators, or omnivores. fungi penetrate the root cortex to form an intimateThe different types of nematodes can be distinguished relationship with host cortical cells. In both symbio-by their mouthparts. Plant parasitic nematodes have ses the integrity of the plant cell membrane remainsa characteristic stylet with a basal bulb, to penetrate intact and is the site of nutrient exchange with theroots. Bacterial feeders have a wide mouth opening fungus. In general, mycorrhizae improve the nutrientto gather in bacteria. To evaluate the health of a soil, status of the plants (especially for phosphorus), andsome researchers examine the ratio of different types may protect plants from exposure to salt, desiccation,of nematodes. Their functional roles in soils are to feed toxins or pathogens. The plant provides energy to theon bacteria, fungi, and protozoa and in turn release mycorrhizae in the form of carbon compounds. Theplant available-nutrients, feed on other soil organic external fungal hyphae explore more soil volume thanmatter, affecting soil structure and carbon utilization, the root itself, especially for phosphorus. This elementor parasitize plants and animals. is quickly depleted within a zone of 1 mm of the root, and does not move any further in soil. For nitrogen, the depletion zone is 10 mm from the root. The hyphaeProtozoa extend this depletion zone for phosphorous. These fungi increase soil stabilization. Tillage, monoculture, fungicides, and long fallows can deplete mycorrhizalThree types of protozoa can be found in soil: ciliated, populations.flagellated or amoeboid. They are animal cells (whichhave no cell walls, just the cell membrane), and aretherefore susceptible to and good indicators of the Bacteriapresence of environmental toxins. In animals, certaintypes of protozoa can cause disease. In soils, theirprincipal functional role is as primary consumers of Bacteria form the base of the soil food web. Theybacteria. In this way, they regulate bacterial popula- degrade a broad range of organic materials, and sometions, increase the turnover of soil microbial biomass produce antibiotics. Bacteria are the most numerousand organic matter, maintain plant available nitrogen, organisms in soil and represent the highest diversityand decrease establishment of plant pathogens. They of species in soil. Their functional roles include nu-are also food for nematodes and fungi. trient cycling and immobilization and formation of humus. There are bacterial pathogens as well, which may produce allelopathic compounds that are toxic toFungi plants. Because of the diversity of food sources used, rapid reproduction and small size, bacteria are very responsive to changing soil environments and criti-Fungi have diverse roles in soil. They produce diges- cal players in both organic matter decomposition andtive enzymes and function as primary decomposers. nutrient cycling.They can be saprophytes, predators of nematodes,parasites of other fungi or plant pathogens. The pro- Bacteria can also form symbiotic relationships withduction of hyphae by saprophytic fungi can be exten- plants. The primary example of this is the Rhizobiumsive, and forming a dense web in soil, and helping to symbiosis responsible for nitrogen fixation in the rootsimprove soil aggregation. Fungi are the organisms of legumes. Legumes lacking the symbiotic relation-with greatest biomass in soil. Symbiotic fungi such ship show signs of nitrogen deficiency when grown inas mycorrhizae form associations with plant roots that low nitrogen soils, while nearby plants inoculated withenhance the survival of both plant and fungi. Some the appropriate Rhizobium species do not.4 Organic Vegetable Production
  13. 13. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.Figure 1The soil food web(Source: Soil Biology Primer. 2000. Soil Conservation Society, USDA Natural Resources Conservation Service)The rhizosphere (root surface) is a “hotbed” of activ- growing in sterilized soil produce less biomass thanity for bacteria, actinomycetes, and fungi. Plant roots plants growing in soil where bacteria are present, whichexude or secrete carbohydrates that serve as food in turn produce less biomass than plants growing insources for a number of beneficial and pathogenic soil where bacteria, fungi and higher order consumersorganisms. Roots that are colonized by beneficial or- are present. Regular additions of organic matter fromganisms are less likely to be attacked by pathogens due diverse sources and avoidance of tillage practicesto competition for nutrients, production of antibiotics, and chemical applications that are detrimental to soiland/or parasitism of the pathogens by the beneficial organisms will help maintain a diverse and strong soilorganisms. food web on your farm.A strong food web is needed for optimal nutrientcycling and release. Research has shown that plantsSoil and Nutrient Management 5
  14. 14. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information. Interpreting Soil Test Results and Estimating Nutrient Availability John Howell Extension Vegetable Specialist (retired) UMass Extension University of MassachusettsSoil quality is of major importance to crop health and pore space is filled about equally with water and air.productivity. Soil management practices should striveto protect soil from erosion, maintain or increase or- Mineral soil particles are grouped according to size.ganic matter, provide an environment which promotes Beginning with the smallest, they are classified asa diverse microbial population and create and maintain clays, silts, sands and gravel. Soils consist of mixturesgood soil tilth. A nutrient management program should: of various size particles. Texture is the proportional1) supply sufficient nutrients to achieve the optimum amount of each of these groups. Note that the wordyield that is realistic for the site; 2) avoid excess ap- loam does not refer to a specific group of particles,plication of nutrients which can degrade water quality but is used to describe mixtures of sand, silt and clay.or which create imbalances causing lower yield and/or Soil texture is determined solely by the sizes of thequality; and; 3) maintain desired soil pH, to ensure that mineral particles and has nothing to do with organicall nutrients are readily available to the crop. matter Weathering can change the size of these par- ticles, but only over thousands or millions of years. For all practical purposes, the texture of the soil doesPhysical properties of soil not change. Soil texture has a major effect on the physical andSoil texture chemical characteristics of soil. Sandy soils have rather large particles and large pore spaces (macropores).Soils are composed of solid particles with spaces be- Clay soils have very tiny particles with very small poretween them. The soil particles consist of tiny bits of spaces (micropores), but because there are many timesminerals and organic matter The areas between them more pore spaces, clay soils have greater total poreare called pore space and are filled with air and water. space than sandy soils. Water adheres to soil particles.An agricultural soil should consist of about one-half The force of this can pull water through a soil, evensoil particles and one-half pore space by volume. against gravity. This is called capillary action, and actsIdeally, organic matter will account for 5 to 8% of in the same way water is lifted in a straw or narrowthe weight of soil particles. Moisture content varies tube. In this case, water is lifted farther in a narrowconsiderably with factors such as soil drainage and tube than in a wide one. Capillary action is greater inthe amount and frequency of rain or irrigation. For micro pores than in macro pores. However, if a soil ismost agricultural crops, conditions are best when the compacted, all water movement including capillary6 Organic Vegetable Production
  15. 15. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.movement is limited. Clay soils absorb and retain more soils. Tillage at proper levels of soil moisture causeswater than sandy soils, but are typically poorly drained granulation. Excessive tillage in an effort to prepare aand not well aerated. Sands are well drained as a rule, fine seed bed, especially when soils are dry, destroysbut retain little water. Loams combine some of the soil aggregates. It is very easy to overwork a soil withmoisture retention characteristics of the clays with the a rototiller. Pounding from rain or irrigation wateraeration of the sands and are widely considered the best droplets can also destroy soil aggregates. Soils shouldagricultural soils. Sandy soils are coarse-textured and be managed to create and maintain soil aggregates asare often referred to as “light” because they are easy much as possible. Mulches are an excellent way toto work. Clay soils are fine-textured and their particles protect aggregates from splashing water.will bond tightly together when they dry out after beingwet. These soils can become very hard and difficult to Biological activities are important to the granulationwork and are often called “heavy.” The terms “heavy” process. Earthworms pass soil through their digestiveand “light” do not refer to weight; sands actually weigh systems, adding viscous juices which bind particlesmore per unit volume than clays. together. Snails and other organisms leave a trail of slime behind them which acts as a glue. OrganicSoil structure matter is an important factor in the formation of soil aggregates and it adds greatly to their stability. SoilStructure is another term used to describe physical organic matter, particularly if it is well decomposedattributes of soils. While texture refers to the sizes (humus) is a binding agent which holds clay particlesof mineral particles, structure is the overall arrange- together. It is believed that this is due to chemicalment or aggregation of soil particles. Terms such as unions between humus and clay particles. The endloose, hard-packed, granular and cloddy are among result is that soil organic matter plays a major rolethose used to describe structure. Soil structure can be in granulation. By increasing the stability of soil ag-modified by activities such as tillage, moisture level, gregates, the soil becomes easier to work and doesn’tfreezing and thawing, root growth, earthworms and compact as easily.other soil inhabiting animals, and driving or walkingon the surface. Organic matter not only improves the structure of fine-textured soils, but it is equally beneficial forVery sandy soils nearly always have a loose structure coarse textured soils. Coarse soils have a high pro-and don’t become hard-packed or cloddy. Fine-textured portion of macropores, facilitating gas exchange andsoils can become hard-packed. This condition inter- water movement. However, due to a low proportionferes with root growth, inhibits movement of water into of micropores, these soils are not moisture retentive.(infiltration) and through (percolation) the soil. The This makes frequent irrigation a necessity duringmicro pores in fine textured soils can easily be filled dry periods. Organic matter substantially increaseswith too much water to the exclusion of air, limiting the proportion of micropores, greatly improving thethe exchange of oxygen and carbon dioxide. The mac- water holding capacity of a coarse-textured soil. It isropores of coarse-textured soils facilitate infiltration estimated that for each per cent of soil organic matter,and percolation of water and the exchange of gases, moisture holding capacity is increased by as much asbut they retain little water for crop use. By loosening 16,000 gallons per acre in the root zone.and aggregating a fine textured soil, we can improvewater infiltration, percolation, and gas exchange,and still maintain the ability to retain water for plant Chemical properties of soilgrowth. An aggregated soil consists of granules thatresemble crumbs. A granule consists of many clay orsilt particles clumped together. A well granulated soil Information about a soil’s chemical properties can behas micropores within the granules and macropores provided by a soil test. The soil test report indicatesbetween them and is both moisture retentive and well the levels of the nutrient elements that are availableaerated. for crop nutrition. It also provides information about soil pH, buffer pH, cation exchange capacity, baseNatural activities such as freezing and thawing and saturation and organic matter. If this sounds a bit in-the movement of roots contribute to granulation of timidating, the following discussion should be helpful.Soil and Nutrient Management 7
  16. 16. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.Essential elements these soils. Clearly, you cannot expect to achieve the benefits of other amendments when pH is suboptimum.There are thirteen mineral elements known to be essen-tial for plant growth. All of these nutrients are absorbed Cation exchange capacityfrom the soil. Six of these are called major or macroelements because the plant uses them in comparatively “Ions” are atoms or groups of atoms (molecules)large amounts. They are nitrogen (N), phosphorus (P), which have an electrical charge. “Anions” have apotassium (K), calcium (Ca), magnesium (Mg) and negative (-) charge and “cations” have a positive (+)sulfur (S). Sometimes Ca, Mg and S are referred to as charge. Plants take up nutrients from the soil eithersecondary elements because they are used in somewhat as cations or anions. Many of the nutrient elementssmaller amounts than N, P and K. The other seven are are cations (pronounced cat-eye-ons). These includecalled minor, micro or trace elements. These are ev- Ca++, Mg++, K+, Fe+++, Mn++, Zn++, Cu++ and ammo-ery bit as important as major elements, but are used in nium (NH4+) which is a form of N. Other cations ofvery small amounts. These elements include iron (Fe), importance are H+ and Al+++ (aluminum). Anions ofManganese (Mn), zinc (Zn), boron (B), copper (Cu), importance include nitrate (NO3-), a highly leachablemolybdenum (Mo) and chlorine (Cl). Nickel (Ni) is form of nitrogen.accepted by many scientists as the 14th nutrient elementderived from soils. The level of crop production can Cations are attracted to negatively charged surfaces ofbe no greater than that allowed by the most limiting small clay and organic (humus) particles called col-of the essential elements. loids. This attraction is called adsorption. Generally, cations are held tightly enough on adsorption sites toIn addition to mineral elements, carbon (C), hydrogen restrict their loss through leaching. These cations can(H) and oxygen (O) are essential elements. Plants take move from the adsorption sites on colloids into thethese elements from air and water. Although these ele- soil water solution and vise versa. In the soil solution,ments are not applied as fertilizer materials, our soil they are available for root uptake, but are also subjectmanagement practices affect their availability. to leaching (see Figure 3). Cation exchange capacity (CEC) is a measure of the number of adsorption sitesSoil pH in a soil and is an important indicator of the soil’s ability to retain and supply cations for plant use. CECOne of the most important aspects of nutrient man- is reported as milli-equivalents per 100 grams of soilagement is maintaining proper soil pH. Soil pH is a (meq/100 g). The CEC of agricultural soils rangesmeasure of soil acidity. A pH of 7.0 is neutral. If the pH from below 5 in sandy soils with little organic mat-is below 7.0, the soil is acid, but if it is above this level ter to over 20 in certain clay soils and those high init is alkaline. Most soils in the Northeast are naturally organic matter. A soil with a low CEC has little abilityacid and need to be limed periodically to neutralize to store nutrients and is susceptible to cation nutrientexcess acidity. Soil pH is important because it affects loss through leaching.the availability of nutrient elements for plant uptake.Availability of macro-elements and molybdenum (Mo) Cation exchange capacity is related to soil texture.is restricted in acid soils. Under alkaline conditions, Of the mineral particles, clay is the only group whichwith the exception of Mo, the availability of microele- makes a significant contribution to CEC. However,ments is reduced. Under acid conditions, Ca and Mg there are several types of clays, and they vary con-are frequently low and there may be toxic levels of siderably in their CEC. Crops are grown on a wideiron, aluminum and manganese. Most crops, do best range of soil types, including many that are sandywhen the soil pH is in the range of 6.0 to 6.8. At this and low in clay. In many areas of the Northeast, thepH, the availability of macro and micro elements is types of clay present have a low CEC. In much of themaximized, and accumulation of toxic elements is region’s soils, organic matter is the primary contribu-minimized. Although most soils in the Northeast are tor to CEC. This fact is true even of soils with lowable to supply sufficient amounts of microelements, organic matter. Not only does organic matter improvegrowers may find deficiencies in some of the sandy the physical properties of soil, it also plays a vital rolesoils. A soil pH of 6.0 to 6.2 is more appropriate for in soil chemistry by increasing CEC.8 Organic Vegetable Production
  17. 17. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.Base saturation recognizable characteristics for a while. This is the dead fraction of the SOM. It is also called the activeThe cations Ca++, Mg++, K+ and H+ normally account for fraction because it supports microbial activity. Soonernearly all cations adsorbed on soil particles, although or later the dead organic matter decays due to microbialtrace elements that are cations are also present in activity and cannot be recognized for what it was andminute quantities. Ca++, Mg++, and K+ are base cations eventually becomes humus. This is very dead organicthat raise soil pH and H+ and Al+++ are acidic cations matter. It is also called inactive organic matter becausethat lower soil pH. If all of the adsorbed cations are it will no longer support microbial activity. In addition,bases and none are acidic, there would be a 100% base animals eat plants or other animals and pass some ofsaturation, and the soil pH would be about 7 (neutral) their food through their bodies as manure which is richor above. In acid soils there are acid cations pres- in nutrients and organic matter.ent and the percent base saturation is less than 100.Besides having sufficient quantities of Ca, Mg and Organic matter consists of numerous compoundsK, they should be in balance with each other because which vary greatly in their ease of decomposition.an excess of one of these can suppress the uptake of Sugars, starches and proteins are rapidly decomposedanother. As a general rule a Ca:Mg:K ratio of about by microbes while lignin, fats and waxes are resistant20:4:1 is desirable. When expressed as percent base to this process. Fresh organic residues consist mostlysaturation, desired levels are: Ca 65-80%; Mg 5-15%; of easily decomposed compounds which break downand K 2-5%. rapidly under favorable conditions. The result is a rapid reduction of the volume of SOM. The resistant materi-Soil organic matter als remain and form the dark colored material called humus. Humus continues to decompose, but at a veryAs already noted, soil organic matter (SOM) improves slow rate. Carbon dating has shown some humus tomoisture holding capacity of sandy soils, aeration be thousands of years old. Humus forms the colloidsof clay soils and helps overall structure of any soil. which contribute to increased cation exchange capacitySoil organic matter is the chief contributor to cation and good soil structure.exchange capacity in many soils and is an importantfactor in all soils. The break down or decomposition of Soil organic matter is broken down by microbes asSOM releases nutrients which can be used by plants. they consume it for food. Any factor that affects soilOrganic matter is also food for organisms that are es- microbial activity also affects SOM break down. Insential for a healthy soil environment. the microbe, respiration combines most of the carbon from SOM with oxygen to form carbon dioxide gas.By definition, organic matter contains carbon. Carbon For this process to continue, there must be an exchangeis a source of energy for microorganisms (microbes) of oxygen and carbon dioxide between the atmospherein the soil. These are microscopic plants and animals and the soil pore spaces. Gas exchange can be restrictedsuch as bacteria and fungi. Some of these are patho- if the soil is compacted or saturated with excess water.gens which cause plant disease, but in a healthy, This slows the rate of SOM decomposition. Whilewell managed soil the vast majority are beneficial. excess water inhibits decomposition, a certain amountOrganic matter provides food for a diverse popula- is necessary to support microbes. Therefore, condi-tion of microbes in the soil and this helps prevent tions of moisture stress can be expected to slow theany one type of organism, such as a plant pathogen, decomposition of SOM.from dominating. Soil microbes are also influenced by soil pH and tem-Soil organic matter is continuously being produced perature. This is especially true of bacteria. Under acidand broken down by living plants and animals. Dr. conditions, bacterial activity in breaking down organicFred Magdoff of the University of Vermont coined an matter is greatly reduced. Soil fungi responsible forappropriate phrase: There are three kinds of SOM; the break down of SOM are generally less affected byliving, the dead and the very dead. The living fraction low pH. In most cases, however, bacteria are respon-of the SOM is made up of living plants and animals, sible for most of the decomposition of SOM, and asincluding microbes, that are found in the soil. When a rule this process is markedly slowed if soil pH levelthey die, stalks, leaves and other plant parts retain drops below 6.0. The optimum soil temperatures forSoil and Nutrient Management 9
  18. 18. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.bacterial activity are in the 70 to 100° F range, but there are required intervals between application ofactivity occurs as low as 40° F, although at greatly manure and harvest of edible crops. Check with anreduced rates. accredited certifying agency.A moist, warm, well aerated soil with a pH betweensix and seven provides ideal conditions for decompo- Soil testingsition of SOM. These are the conditions that promoteoptimum growth of most crops. Productive farmingpractices can be quite destructive to SOM! This may Sampling a fieldseem frustrating if you are trying to build SOM, butdecomposition is a beneficial process. It provides To collect a soil sample, use a soil probe, soil auger,energy for a diverse group of soil microbes, releases or garden shovel to collect samples from throughoutnutrients for plant growth and produces humus. The the field. Use a “V” or “W” pattern to ensure that thechallenge is to continuously replace what is lost and, sample is representative of the field. Areas of the fieldif practical, increase SOM. that appear to be a different soil type, have been man- aged differently, or where you have observed poorAdding to soil organic matter growth, should be sampled separately.Compost is an excellent source of organic matter that Scrape away surface litter from the sites you choose,nearly all farmers can make. Most growers don’t have and then collect a core or slice of soil to the plowenough raw materials to satisfy their needs. Some are depth—usually about 6-8 inches. Collect cores frombringing in additional materials such as municipal 10-15 different sites and place them in a plastic bucket.yard wastes to compost on site. Others are purchasing Mix these samples well, and then take about one pintcompost from the increasing number of commercial of soil from this mixture to send to the lab. It is best tocomposters. Regardless of the source, compost should air dry this sample before you send it to the lab.be finished before use. Finished compost has no recog-nizable bits of matter and will not heat up after turning. The report you receive from the lab should indicate soilCompost should be tested for nutrient content. Most nutrient levels of most of the macronutrients and somesoil testing laboratories can test compost. Finished of the micronutrients, pH, and organic matter. Somecompost should have a low ammonium content, high labs also include cation exchange capacity, buffer pHnitrate level and a pH near neutral. Repeated use of a or exchangeable acidity, and/or base saturation.compost high in a particular element may cause a nu-trient imbalance and result in excess levels of certain Adjusting pHelements. This can easily be avoided by soil testing ona regular basis (at least every three years). Lime is used to correct the pH of acid soils. The amount of lime needed depends on several factors, includingAnimal manure is an excellent source of nutrients and current and desired pH, soil texture and soil organicorganic matter. About half of the nitrogen in fresh dairy matter. Soil testing laboratories measure soil pH, whichmanure and 75% of the nitrogen in poultry manure is is actually a measure of the concentration of H+ in thein the form of ammonia. Ammonia is subject to loss soil solution. This is called active acidity. There is alsothrough volatilization if not incorporated immediately H+ adsorbed onto soil colloids. This is called reserve (orafter spreading. In the soil, ammonia is converted to exchange) acidity and this is related to cation exchangenitrate and is available for plant use. However, since capacity (CEC). When lime is added to the soil, reac-nitrate is subject to leaching, large applications should tions occur which result in H+ being replaced by Ca++generally be avoided. There are times when readily and/or Mg++. At the same pH, a soil with a high reserveavailable nitrogen is needed, but fresh manure should acidity (loams, clays, high humus) may require 3 to 4be applied with caution. Many people prefer to com- times as much lime as one with a low reserve aciditypost manure before field application. This stabilizes the (sands, gravels). The soil testing laboratory uses anitrogen. Manure can be mixed with other materials procedure to determine the lime requirement of a soilfor composting. There are strict certification re- based on its reserve acidity. A buffer pH test is the mostquirements for composts that contain manure and common method used to determine lime requirement,10 Organic Vegetable Production
  19. 19. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.but some laboratories use other procedures. years can lead to an imbalance between Ca and Mg. Because dolomitic lime is the most readily availableThe speed with which lime reacts in the soil is depen- liming material in some areas, many growers havedent on particle size and distribution in the soil. To used it continuously. As a result, many fields are lowdetermine fineness, lime particles are passed through in Ca and very high in Mg. Choose liming materialssieves of various mesh sizes. A 10 mesh sieve has 10 to achieve and maintain appropriate base saturationopenings per linear inch, or 100 openings per square levels. Shop around for and insist on the appropriateinch (10 X 10) and a 100 mesh sieve has 10,000 material, even if you must pay for increased haulingopenings per square inch (100 X 100). Lime particles costs. Gypsum may be used to increase Ca if calcitethat pass through a 100 mesh sieve are fine and react is not available, but it does not affect soil pH and israpidly—within a few weeks. Coarser material in the expensive.20 to 30 mesh range will react over a longer periodsuch as one to two years or more. Agricultural ground The neutralizing power of lime is determined by itslimestone contains both coarse and fine particles. calcium carbonate equivalence (CCE), also referred toAbout half of a typical ground limestone consists of as Effective Neutralizing Value (ENV). Recommen-particles fine enough to react within a few weeks or dations are based on an assumption that lime is puremonths, but to be certain you should obtain a physical calcium carbonate which has a CCE (ENV) of 100%.analysis from your supplier. If lime has a lower CCE (ENV), more than the recom- mended amount is needed, but if it is higher, as withSuper fine or pulverized lime is sometimes used for a some dolomitic limes, less is required. To determinequick fix because all of the particles are fine enough the amount of lime to apply, divide the recommendedto react rapidly. Hydrated lime, “quick lime” are fast amount by the per cent calcium carbonate equivalenceacting, but are not approved for use in organic systems of the lime to be used and multiply by 100. For ex-because they are highly caustic. ample, if the lime recommendation is 2 tons per acre and the lime has a CCE of 72%, apply 2.7 tons per acreFor the most rapid results, lime should be thoroughly according to the following calculation:mixed with the soil. Plowing turns lime under to theplow depth, but does not mix it with the soil. Harrow- recommended amount X 100% = amounting can do a good job of mixing, but generally only CCE neededincorporates lime to a depth of two to three inches. Asplit application can be use in which half the lime is ORplowed under, and the remainder is applied after plow-ing and harrowed in. A rototiller is effective for soil 2 tons/A X 100% = 2.7 tons/Aincorporation. Weather permitting, it is best to apply 72%lime when the soil is somewhat dry. If lime is spreadon damp soils, it tends to cake and will not mix as Wood ashes can also be used to raise soil pH. Thewell with soil particles. If the soil pH is already at a calcium carbonate equivalence of wood ashes variesreasonable level and rapid results are not needed, lime considerably, typically ranging from 30 to 50%. Theymay be recommended to maintain current levels. In are chemically similar to quick lime and supply K asthis case plowing or simple harrowing are sufficient well as Ca and Mg. CAUTION: Do not over-applyfor incorporation. wood ashes. Wood ashes spread in a concentrated area cause the soil pH to become extremely high, inhibitingBesides raising soil pH, lime is the most economical plant growth.source of Ca and Mg for crop nutrition. Select limingmaterials based on Ca and Mg content with the aim of On some soils, it may be necessary to lower the pH.keeping these nutrients in balance. If the Mg level is Elemental sulfur can be used for this purpose. Likelow, a lime high in Mg (dolomite) should be used. If Mg limestone, particle size and thoroughness of mixingis high and Ca is low, a lime high in calcium (calcite) affect the speed of reaction. It typically requires sixis preferable. “High Mag” lime contains about 5% Mg months to a year to lower pH to the desirable range.and 35% Ca by weight. Use this if both Ca and Mg are The ability of sulfur to lower pH varies among soils.needed. Continual use of one type of lime over several Sulfur must be oxidized to be acidifying. This processSoil and Nutrient Management 11
  20. 20. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.is carried out by certain bacteria. If they are not pres- calcium and magnesium at high pH. Added fertilizerent in the soil, this reaction, and hence, acidification phosphorus is fixed with other elements and is onlywill not occur. very slowly made available. Since this is a chemical reaction, it is faster in warmer soils than in cooler soils. Banding P with a material such as bone meal, ratherNutrient management than broadcasting, is a more efficient way to apply this nutrient if needed. Manure is a good source of easily available P.Macronutrients PotassiumNitrogen Potassium is the third of the “primary elements.” CropsNitrogen is often the most limiting nutrient. Deficiency deficient in K can suffer considerable loss in yield orsymptoms include yellow plants and stunted, weak quality without showing obvious symptoms. This isgrowth. The majority of crops absorb most of their often called hidden hunger. In severe cases, leaf edgesnitrogen in the nitrate (NO3-) form, but they can ab- may be scorched. Plants absorb potassium in the ionsorb some ammonium (NH4+). Unfortunately, nitrate- form K+. Potassium can be leached from sandy ornitrogen is very soluble and is easily leached. In most gravelly soils of low CEC and be fixed and unavail-soils, a considerable amount of nitrogen is tied up in able in some clays.organic matter (crop residues, soil organic matter, mi-crobes, etc.) not immediately available to plants. This Calciumnitrogen must be released by microbes as they consumeorganic matter. This process is called mineralization Calcium is absorbed by roots in the ion form Ca++.These microbes are most active when the soil is warm, Deficiency symptoms include young leaves that aremoisture and aeration are optimum and pH is 6.0 or stunted, distorted and spotted and necrotic at the leafabove. Cool conditions, dry or waterlogged soils, low edge. Blossom-end rot is seen in tomatoes and otherpH or compaction will slow the conversion of nitrogen fruiting crops. Although calcium may be present into available forms. Under favorable conditions, we can high levels in the soil, dry conditions will limit itsusually expect from 20 to 40 lbs. of nitrogen per acre uptake by plants and cause deficiency symptoms.for each per cent soil organic matter. High levels of sodium, K, Mg, and ammonium may also cause deficiency by interfering with Ca uptake.Nitrogen uptake varies from as little as 50 lb./A forsnap beans to 200 lb/A or more for field corn. Soil Magnesiumorganic matter can provide some and in some cases allof a crop’s need for nitrogen. The rest can be provided Magnesium is absorbed in the Mg++ form. Deficienciesby adding an organic fertilizer. Manure can supply appear on older leaves as regions between leaf veinsa substantial amount of readily available nitrogen. which become yellow and sometimes a reddish colorFor safety reasons and to meet certification require- progressing to brown. Deficiency is most commonments, a minimum time interval is required between on acid, highly leached soils or those that are high inapplication of non-composted manure and harvest of potassium or calcium.edible crops. SulfurPhosphorus Sulfur is cycled through soil in a very complex fashion,Phosphorus, like nitrogen, can be found in organic and similar to nitrogen. In the northeast, significant quanti-inorganic portions of the soil. P deficiency appears as a ties of sulfur are supplied by air pollution. Deficiencypurpling of leaf tissue. P is found in three forms in soil; symptoms, while rare, first appear as a yellowing oftwo of which are unavailable to plants. The unavail- the younger leaves (as compared to older leaves withable forms include P in organic matter and phosphorus nitrogen). Sulfur deficiency is more likely in acid,fixed or bound to iron and aluminum at low pH, and sandy soils, low in organic matter.12 Organic Vegetable Production
  21. 21. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.Micronutrients (lb/A). This is not usually very helpful to a grower, but the report also has a rating of low, medium, highMicronutrients are not often deficient. Deficiencies (optimum) and very high (excessive). These ratings areare more likely in soils with high pH or sandy soils useful in determining the need for nutrient applications.with low organic matter. Some of the more commonelemental deficiencies are mentioned below. Generally, it is best to have nutrient levels in the high/optimum range. This means that for most crops,Iron deficiency there is an adequate supply of nutrients. If a nutri- ent is in the medium range, it is likely to limit cropIron deficiency appears as a white or yellow area production, but not severely. In such cases, crops canbetween the veins of youngest leaves. It is most com- be expected to respond to application of the nutrientmonly seen on soils with higher pH and can often be some extent. If a nutrient level is in the low range it isworsened by liming. Excess P can tie up some iron likely that it will limit production to a greater extent.as well. In this situation, increasing the level of the nutrient element will probably benefit the crop significantly.Manganese deficiency Conversely, if a nutrient is in the very high/excessive range, it may interfere with the availability of certainManganese deficiency can result in yellowing of the other nutrients which are otherwise in adequate sup-interveinal areas of young leaves (as compared to older ply. Excess levels of nitrogen and phosphorous alsoleaves for magnesium). It is most common on soils create potential hazards to water quality, and in thewith pH above 6.8. case of nitrate-nitrogen in drinking water, can have serious health effects.Zinc deficiency One of the goals of a soil management program shouldZinc deficiency often shows as small, abnormally be to maintain nutrient levels in the high/ optimumshaped leaves and stunted plants. As with iron, excess range. If a nutrient is in or is approaching the veryP can tie up zinc. high/excessive range, it should not applied until the level drops back into the high/optimum range. ThisBoron deficiency is challenging for organic growers, because many amendments such as compost contain a number ofBoron deficiency may result in browned, distorted, different nutrients. If a material is used, it may supplybrittle plants. Fruit may be affected by cracks, necrotic some needed nutrients, but may also increase the levelspots, and internal breakdown. Stems of cruciferous of nutrients already in excess. Also, many materialscrops may be hollow. It may occur on alkaline, highly are slow to release nutrients and may continue to doleached, or low organic matter soils. Caution: some so after levels are in the very high/excess range. Thecrops are sensitive to high levels of boron; don’t ap- best way to avoid excess nutrient levels is to test theply more than two lb per acre. Solubor or boraxo are soil regularly and be aware that many materials willapproved sources for organic agriculture. continue to increase soil nutrient levels for some period of years after application.Determining what nutrients to addand how much Pre-sidedress soil nitrate testThe only way to know the nutrient needs of a soil is by The pre-sidedress soil nitrate test (PSNT) was origi-testing. Guess work is dangerous. There are numerous nally developed to improve nitrogen management inexamples of fields with serious nutrient imbalances field corn on farms with a significant amount of ma-and excesses where they were not monitored by soil nure usage. It has been adapted for use in vegetabletesting. Most soil test reports indicate nutrient levels crops to predict the need for applying supplementalin terms of parts per million (ppm) or pounds per acre nitrogen during the growing season. Regular soil testsSoil and Nutrient Management 13
  22. 22. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.performed in the fall, winter or spring do not provide an Organic fertilizers often improve soil organic matteraccurate indication of nitrogen levels in the soil during and generally have a positive impact on soil tilth.the growing season. The PSNT can also be a useful tool They are easy on earthworms and microbial popula-for organic growers to monitor nitrogen levels during tions. However it is possible to achieve excess levelsthe summer, when this nutrient is normally at its high- of some nutrients if some amendments are applied atest levels. This allows the grower to adjust applications high rates over a period of time. This can be avoidedof nitrogen containing amendments, such as compost by monitoring levels by regular soil testing.to avoid excesses of deficiencies. A nitrate-nitrogenlevel of 30 ppm measured in early summer is believedto be adequate for most crops. Levels above 50 ppm Referencesare considered excessive.To sample for the PSNT, collect 15 to 20 subsamples Brady, Nyle C. 1974. The Nature and Properties offrom the top 12 inches of soil about one week before Soils. 8th edition. MacMillan Publishing Co. Newthe pumpkin vines begin to run. Mix the subsamples York.and retain about one cup full for the test. Soil samplesshould be spread on a nonporous surface to air dry Garrison, Steven, ed. 1999. Commercial Vegetablesoon after sampling. Follow the general directions for Production Recommendations for Delaware, Mary-collecting soil samples described on page 10 in this land, New Jersey, Pennsylvania and Virginia. Coopera-chapter. When the soil is dry, send your sample to a tive Extension Systems of Delaware, Maryland, Newsoil testing lab for a nitrate-nitrogen test. Jersey, Pennsylvania and Virginia Heckman, Joseph. 2002. Personal communication.Organic fertilizers Howell, John C., ed. 2002. 2002-2003 New England Vegetable Management Guide. Cooperative ExtensionNutrients need to be added to fields to replace those Systems of New England.which have been removed by harvesting. If a soil islow in a nutrient(s), extra effort is needed to achieve Howell, John C. 1998. Soil Basics I, II and III. Univer-suitable levels for optimum production. Organic sity of Massachusetts Extension Fact Sheets: VegSFfertilizers include animal manures, compost, green 1, 2 and 3-98manures, and other natural materials. Many of theseare slow to become available to plants, but contribute Magdoff, Fred. 1992. Building Soils for Better Crops:to soil fertility in the long run. Some are available Organic Matter Management. University of Nebraskamore rapidly and are useful to correct a problem or to Press. Lincoln.supply certain nutrients while fertility is built up withother amendments. Some common organic fertilizers Sachs, Paul D. 1993. Edaphos: Dynamics of a Naturalare listed in Table 1 along with typical nutrient values Soil System. Edaphic Press. Newbury, Vt.and relative availability. The list of allowed inputssometimes changes, so it is important to consult with Pohl, Susan, ed. 1994. Vegetable Production Hand-an accredited organic certifying agency to determine book. Cornell Cooperative Extension.what fertilizer materials are currently allowed.14 Organic Vegetable Production
  23. 23. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information. Table 1 Organic Fertilizers. Check with certifying agent on current status. Material N (%) P2O5 (%) K2O (%) Relative Availability Alfalfa pellets 3 0.5 3 slow Dried blood 13 2 0.5 med/rapid Bone meal (raw) 2-6 15-27 0 slow/med Bone meal (steamed) .5-4 18-34 0 slow/med Cocoa shells 1-2 1 2-3 slow Compost (unfortified) 1-3 .5-1 1-2 slow Compost (fortified blends) 3-5 3-4 3-5 slow/med Cottonseed meal 6 2 2 slow/med Fish emulsion 4-5 1-2 1-2 rapid Bat guano 6 9 2 med Manure (fresh) dairy .5 .2 .5 med/rapid horse .6 .2 .5 med sheep 1 .3 1 med/rapid poultry 1-3 1-2 .5-2 med/rapid Pumace (fresh apple) 6-7 1-2 .2 slow Soybean meal 6-7 1-2 2 slow/med Tankage (dry) 6-7 10-14 0 med Wood ashes 0 1-2 3-7 rapid Colloidal phosphate 0 18-25 0 slow; about 3% available Granite dust 0 0 3-5 very slow Greensand 0 0 4-9 very slow Rock phosphate 0 20-32 0 slow; about 2% available Sodium (Chilian) nitrate 16 0 0 rapid Sul-Po-Mag 0 0 22 rapid; also contains Mg and S Epsom salts 0 0 0 10% Mg-rapid Nutrient content varies with origin and handling; availability depends on fineness of grind.Soil and Nutrient Management 15
  24. 24. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information. Tillage Practices for Maintaining Soil Quality Harold van Es Department of Crop and Soil Sciences Cornell UniversityHealthy soil is the foundation of sustainable crop through denitrification, and well drained soil can loseproduction. It is the result of a combination of factors. nitrogen through leaching. In the past decades, agri-While this presentation will focus mostly on how till- culture has too much focused on the chemical aspectsage affects soil health I first want to briefly go over the of soils and insufficient attention has been given to the“bigger picture” of soil health. physical and biological (especially) functions.A key concept for managing soil health is recognizing The key management approaches that can positivelythe interaction between the biological, chemical, and influence soil health are organic matter additions,physical aspects of soil. Biologically healthy soil has reduced tillage, and compaction prevention. Addinglow pest populations, or the ability to suppress pests, organic matter to the soil increases biological activityand is fully functional with respect to nutrient cycling and diversity, which in turn releases plant-availableand producing plant growth promoting compounds. nutrients and holds them in the soil, increases soil ag-From the chemical perspective, healthy soil has ad- gregation, pore structure, and tilth, produces humusequate levels of available nutrients, but not so high and other plant growth promoting substances, andthat there will be a lot of leaching; an optimal pH for reduces soilborne diseases and parasitic nematodesthe planned crop rotation; and low levels of toxic or (Fig. 1). At least one long term cropping experimentdisruptive substances such as heavy metals, aluminum, has shown a yield increases related to increasing or-or salts. The physical characteristics of healthy soil ganic matter levels, especially in dry years when higherinclude good tilth, water infiltration, aeration, and organic matter levels can improve water retention.water retention. Now we’ll move on to tillage. One question we canThe biological, chemical and physical properties mu- ask ourselves is why we till in the first place. The plow,tually influence each other, and if we ignore one, the which was invented in the England in the mid-1700s,other will be affected. For example, aggregation of soil revolutionized agriculture. It provided unprecedentedparticles is influenced by the types of cations (e.g. Ca, control of weeds, allowed for a more stable foodMg, K) and amount of organic matter present in the supply, and was a critical tool in the development ofsoil. The types of organisms present can be influenced virgin lands in North America. Plowing the soil incor-by compaction and availability of food sources, and porates residue from the previous crop, weeds, andsoil drainage influences the amount of nitrogen avail- amendments. It’s the first step in seedbed preparation,able to plants because saturated soil can lose nitrogen increases the conversion of organic matter to plant-16 Organic Vegetable Production
  25. 25. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information. Add organic Increased biological activity matter (& diversity) Reduced Decomposition soil-borne diseases, Aggregation parasitic nematodes increased Nutrients Pore structure Humus and other released improved growth Harmful promoting substances Improved tilth substances detoxified and water storage HEALTHY PLANTSFigure 1available nutrients, and reduces compaction, at least oxidized the soil organic matter and released nutrientstemporarily. So, the first experience with the plow was for his crops. In time, however, he mined the soil ofvery positive, mainly because the destructive qualities its nutrients and food source for soil organisms. Indidn’t manifest themselves until after several decades. the long run this is not sustainable, and we have seen similar problems with modern farming methods. OneIn that respect, it is interesting to study the contribu- interesting lesson learned from Tull’s work is thattions of the eighteenth-century English agriculturalist short-term research does not always provide the rightJethro Tull. Tull made an everlasting contribution to picture.the worlds by inventing the seed drill, as he recognizedthat good seed placement improved germination and There are also other negative aspects of plowing. Itplant population over the conventional broadcast uses a large amount of energy, and repeated plowingseeding (of small grains). Now, we recognize that the destroys soil aggregates, which increases compactionmechanical seeder is an essential agricultural tool, and the potential for crusting, resulting in low waterespecially for conservation farming because no-till infiltration, increased erosion, and the development ofplanters allow us to place seeds with very minimal a zone of low microbial activity near the soil surface.tillage. Tull, however, also appears to have done an Intensive soil tillage exposes the soil to the elementsunintentional disservice to the land. He believed that and causes temperature and heat extremes near theplant roots absorbed nutrients as tiny soil particles surface, creating an environment that is uninhabit-(rather than as ions as was established in the following able for soil organisms. In that respect, we need tocentury). He therefore tilled his soils over and again start changing our somewhat romantic image of cleanto pulverize it. Sure enough, he was able to feed his tillage, which we often associate with goodness andcrops for many years without the use of manure or tradition. What could be better than a beautiful, aro-other forms of fertilizer. But what was he doing? He matic freshly-plowed field? In fact, we are actuallySoil and Nutrient Management 17
  26. 26. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.doing something very unnatural, because soil is not do not have the large pores that readily drain and allownaturally exposed to the elements and we are creating air into it. When the soil dries, compacted soils morean ecologically unfavorable soil environment. A field readily experience drought stress, which is actuallycovered with residues may not have the aesthetics of a caused by hard soil not allowing for root penetration.plowed field, but it is a lot more ecologically compat- So crops growing on compacted soil are “happy” onlyible. Farm ugly, as they say. when the moisture conditions are “average.” During prolonged dry or wet periods, however, the plantsAnother factor associated with increased soil degrada- quickly become stressed and have decreased yield ortion is driving heavy farm equipment on a field. The quality. A well-structured soil will not show droughtweight of heavy equipment is concentrated in a small or aeration problems unless the conditions are veryarea underneath the tires, and can certainly increase extreme.soil compaction, especially if the soil is wet. The levelof compaction is greater and extends deeper into wet So how do we improve soil health? First, we have tosoil than into dry soil, reminding us of the importance recognize that some soils have become “addicted”of staying off fields when the soil is wet. to tillage. Depletion of organic matter over time has resulted in soils that are so compacted that multipleThe notions of water availability and compaction are passes are needed to break up clods to create a goodbrought together in the concept of the “optimum water seedbed. The relief is only temporary, however, asrange.” Highly compacted soil has a smaller optimum these soils usually settle back down and form crustswater range than a well-structured soil (Fig. 2). During after the first good rain, inhibiting seedling emergencewet periods, compacted soils experience prolonged and root growth. What can we do to remediate suchwater saturation and aeration problems, because they soils or prevent them from occurring in the first place?Figure 218 Organic Vegetable Production
  27. 27. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.Building Healthy Soils ing no-till, strip till, ridge till, and zone till. The cooler soils associated with no-till can be a challenge in the Northeast. Strip, zone, and ridge till are adaptationsIn general, the following practices will help build soils: of no-till that can overcome some of the cool soil problems. The narrow tilled zone warms up faster1. Organic Matter Management due to the removal of a small amount of residue, and is loosened and aerated, creating more favorable• Add organic matter to the soil regularly. conditions for germination and growth. My research program has shown that no till is most successful when• Use different types of organic materials. used with crop rotations rather than in monoculture. Also, we found that using ridges or beds, which force• Use different sources of organic materials controlled traffic, are very attractive for our climate conditions, especially on medium and fine-textured• Reduce organic matter losses soils. No-tillage is generally very successful on sandy and gravelly soils, which have less compaction prob-• Keep soil surface covered with living vegetation lems and are more drought sensitive. as much as possible We have learned that a good no-till seeder is a criti-2. Improved tillage cal piece of equipment, because it allows for good seed placement under a range of conditions. Many• Minimize tillage intensity times, farmers perform intensive tillage just to create a seedbed, while fine tilth is only needed in the soil• Optimize timing immediately surrounding the seed. With a no-till or zone-till planter, tillage options are much more flexible.• Maximize surface cover If serious cover cropping is part of the management of the farm, a no-till drill is essential. There should3. Minimize soil compaction be no tillage prior to cover crop seeding, because that mostly negates its benefits. Recent studies conducted• No traffic on wet soils (by far most important) in Michigan suggest that even when cover crops or manure are used in a rotation, soil organic matter levels• Minimize soil loading by reducing equipment don’t increase when a moldboard plow is used for till- weight and spreading the load with multiple axles age. Tillage practices such as no-till, zone-till, strip-till, and large tires and ridge-till do result in an increase in organic matter, even when cover crops are not used. In other words,• Use controlled traffic lanes, and take advantage of the less the soil is disturbed, exposing organic matter ridges and beds to the air, the less organic matter is oxidized and lost to the atmosphere.Reducing tillage results in many changes in the soilincluding higher carbon (organic matter) levels, bet- Mulching is another practice that can benefit soil healthter structure, better water availability, more biological by providing cover for the surface of the soil and pro-activity, and reduced erosion. viding a source of organic matter. The use of mulches enhances water availability by improving infiltrationOther changes to keep in mind are that soils may also into the soil and reducing evaporation from the soil.stay cool later in the spring, nutrients may become Mulching provides weed control by shading the soilstratified (higher levels near the surface) because they surface and inhibiting weed germination, reducesare not being mixed into the soil profile, and the pH splashing of soil and disease inoculum onto leaves andof the surface soil will change more rapidly after ap- fruit, and reduces infestations of certain insects (i.e.plications of lime because the lime is not being mixed Colorado potato beetle) on plants grown in a mulchwith a larger amount of soil. system. Also, the temperature and moisture modera- tion from a covered soil promotes biological activity.There is a range of options for reduced tillage, includ-Soil and Nutrient Management 19
  28. 28. This page is from Organic Vegetable Production, NRAES-165. To purchase the book, visit www.nraes.org, or call (607) 255-7654. Page 1 of this PDF has fair use information.While bringing cut mulch into a field is feasible on soil types, and the climate. What works for one growera small scale, a different approach is needed for us- in one part of the state may not work for another growering mulch on a larger scale. Steve Groff, an innova- in another part of the state. Choose a system that is mosttive farmer in southern Pennsylvania has adapted a efficient in terms of energy use and passes across thetechnique for planting into standing mulch that was field, can handle organic matter additions in the formsdeveloped by USDA researchers. Steve uses a no-till available to you, and is appropriate for your manage-seeder or transplanter to establish a crop into the mulch ment style and operation. Be aware that a there is oftenfrom a killed rye/vetch cover crop that was planted a yield reduction that lasts 2-3 years when changing toin the fall of the previous growing season. The cover minimal tillage systems on unhealthy, degraded soils.crop is killed either with herbicides or by a piece of Start small and develop a system that works for youequipment that rolls down and crimps the cover crop before using it on your entire farm.just as it starts to flower. You can learn more about thistechnique from Steve’s web site: <http://www.cedar A good resource for learning more about soil healthmeadowfarm.com/>. is: Building Soils for Better Crops by Fred Magdoff and Harold van Es. It’s available from the SustainableWhat type of tillage makes the most sense on any par- Agriculture Network, <http://www.sare.org/>.ticular farm? It depends…on the type of operation, the20 Organic Vegetable Production

×