Assessing the Pasture Soil Resource


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Assessing the Pasture Soil Resource

  1. 1. Assessing the Pasture Soil Resource A Publication of ATTRA—National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.orgBy Preston Sullivan This technical note provides methods to determineNCAT Agriculture biological activity of pasture soils and practical tipsSpecialist on improving the usefulness of typical soil andPublished 2001 plant samples. The soil biology sampling methodsUpdated April 2010 are easy to learn and utilize commonly availableBy Hannah Sharp tools found around any farm. Once these biologi-NCAT Intern cal assessments are made, more insight into the© NCAT many benefits of nutrient cycling becomes appar- ent. Methods for strategically using soil and plant samples are also covered.ContentsMaking fertilityassessments .................... 1Assessing soil biological Introductionactivity and health ........ 2When to make these Making fertility assessments Aassessments .................... 2 typical soil analysis will provide aEquipment needed ...... 3 guide to the current plant nutrientLocating sample sites ... 3 levels in a pasture soil. For an analysisPoints of assessment .... 3 to be accurate, good sampling procedure must Photo by Susan Tallman, NCAT. 1) Living organisms .... 3 be followed. Before sampling a pasture soil: 2) Earthworms .............. 3 1. Visit the county Cooperative Exten- ridge tops and will be glad you sampled 3) Soil smell ................... 4 sion Office and get their guide on soil top, side and end slopes separately. 4) Aggregation ............. 4 sampling procedure. 5) Water infiltration .... 4 5. Make sure that sampling depth matches the 6) Soil compaction ..... 4 2. Look across the landscape and locate all depth that the soil test report will be based hotspots. Hotspots are areas of excessive on. Many agronomists advise taking pastureConclusion ........................ 5 or unusual nutrient concentration, such samples at 3 or 4 inches deep because mostReferences ........................ 6 as soils around feed bunks, hay feeding of the grass roots are in the top 4 inches.Further resources ........... 6 areas, shade trees, watering sites, loafing The prescribed depth should be in the soilAssessment sheet ......... 7 areas and wet spots. sampling procedure from your Cooperative Extension Office. If you do take a sample at 3. Sample these hotspots separately, or avoid a depth other than the one the lab specifies, them during your sampling. make note of it on your sample sheet so the 4. Sample according to apparent patterns lab can adjust accordingly. such as slope and previous fertilization. 6. Prepare the sample for shipping according When field areas appear dissimilar, sam- to the lab’s recommendations.ATTRA—National SustainableAgriculture Information Service ple them separately. Nutrients tend to( is managed flow downhill in pastures, meaning that Producers generally have the choice of usingby the National Center for Appro-priate Technology (NCAT) and is top slopes will tend to have lower nutri- a private laboratory or the state universityfunded under a grant from the ent levels and the down slope will tend lab to do their soil analysis. Commercial labsUnited States Department ofAgriculture’s Rural Business- to have higher levels. Mixing soil samples cost more but generally have a quicker turn-Cooperative Service. Visit the from all over the pasture will mask these around time and a more complete soil testNCAT website ( for differences and lead to wasted fertilizer report than university labs. Though hotlymore information on dollars. When it comes time to buy fer- contested by some researchers, soil analysisour sustainable agri-culture projects. tilizer, you may only need to fertilize the featuring the base saturation percentages
  2. 2. provides useful information for making fer- tilizer choices. If you would like to get a sec- Table 3. Soil test analysis between a ond opinion, it may be worthwhile to hire poor area and good area of a pasture a consultant to help you with the sampling Nutrient Poor area Good area and the fertilizer recommendations. Nitrogen — — To back up your fertilization program you Phosphorus OK OK may want to take forage samples to see what Potassium low OK effect the fertilizer had. You can also stra- Calcium OK OK tegically utilize soil and forage tissue sam- pling by making comparisons between Magnesium OK OK poor growth areas and good growth areas, Sulfur OK OK or before-and-after comparisons. The three tables below show some hypothetical examples of strategic soil and plant tissue sampling. Assessing soil biological Forage analysis can be used to judge the activity and health success of a fertilization program by iden- While nutrient status is essential to soil tifying any remaining nutrient deficits. For health and vitality, biological activity andRelated ATTRApublications example, the before-and-after forage analy- soil structure should be appraised to get a sis shown in Table 1 shows that the applied more complete picture. The biological soilNutrient Cycling component creates and maintains many fertilizer met all crop needs for major andin Pastures secondary nutrients. In addition, soil and desirable soil conditions. Many biologicalA Brief Overview forage analysis taken from adjacent poor parameters are quite costly to measure andof Nutrient Cycling and productive field areas can be used to require hours of laboratory time. Others canin Pastures better identify nutrient imbalances. Th is be quite inexpensive and convenient. TheSustainable Soil is illustrated in Tables 2 and 3. Visit your following assessment procedures can be per-Management county extension agent or a private consult- formed in an hour or so using inexpensive, ant to learn effective methods for taking a locally available materials (Holistic Man- forage sample. agement International, 2007). These proce- dures are derived from Holistic Management Table 1. Forage tissue analysis before Biological Monitoring Manual available from and after fertilization Holistic Management International. For a Nutrient Before fert. After fert. more complete cropland assessment, order Nitrogen low OK this publication. Ordering information is Phosphorus OK OK listed in the Further resources section. Potassium low OK Calcium OK OK When to make these assessments Choose a time of year when soil biological Magnesium OK OK activity is high, usually in late spring Sulfur low OK and mid-fall. Select a day when the soil is moist but not wet, after all excess water has Table 2. Forage tissue analysis between drained away. Generally, the soil is right a poor area and a good area for this assessment when you cannot roll Nutrient Poor area Good area the soil into a ball and it crumbles easily in Nitrogen low OK your hand. Phosphorus OK OK Avoid taking samples: Potassium low OK • From wet soils. When the soil sticks Calcium OK OK to your shoes, it is too wet. Magnesium OK OK • During drought periods or times of Sulfur low OK excessive heat.Page 2 ATTRA Assessing the Pasture Soil Resource
  3. 3. • From cold soils. Begin by selecting the first point for evalu- • Within a month following tillage, ation at the sampling site and lay the 1-foot fertilization or liming. diameter ring on the ground. The following assessments are most conveniently done by completing all six at the first point beforeEquipment needed moving on to the second point. • Pencil • Assessment sheet Points of assessment • Clipboard to hold the paper 1) Living organisms • Shovel Clip all the standing vegetation within the • Can or jar capable of holding 16 wire circle down to the ground and remove fluid ounces (1 pint) but no more it. Pull back the soil surface litter and look for • Small round bottle capable of holding signs of living organisms other than plants. ½ cup of water A small hand rake may help in turning the surface litter. Count the number of different • Bucket with 2 gallons of water for kinds of living critters, such as beetles, ants, I each assessment sheet to be filled out millipedes, centipedes, snails and more, on f a pasture is • Watch with a second hand or the soil surface within the ring. Record the highly variable, a stopwatch numbers on the assessment sheet. assess each • Tape measure It is advisable to start turning the surface distinct area • Hand grass clippers litter from the outside of the ring toward separately. In each the center. This forces mobile critters to pasture unit, three • Homemade soil penetrometer, the center where they will be seen by the described below sampling sites observer. If you start at the center and work should be selected. • A wire ring that measures 1 foot toward the ring, the critters have a chance to across, made of wire or flexible pipe escape outside the ring undetected. With this assessment the number of species, or diver- Note: The length of wire required to make sity, is more important than the number of a circle with a 1-foot diameter is approxi- individuals. mately 39 inches, depending on the thick- ness of the wire. Remember to allow some A higher number of different types of organ- extra length to attach the two ends and isms indicates more biodiversity. The more make the ring. Measure the diameter of biodiversity, the better the first stage of the wire ring when the ends are attached decomposition will proceed. to make sure it is 1 foot across. 2) EarthwormsLocating sample sites While still at the circle, count the numberAn individual assessment sheet should be of wormholes inside the ring. The surfaceused for each pasture. If a pasture is highly holes are the vertical burrows of nightcrawlervariable, assess each distinct area separately. worms. After counting the wormholes, insertIn each pasture unit, three sampling sites the shovel to its maximum depth and turnshould be selected. Use field maps, com- over the shovelful of soil. Break the soil apartpasses, landmarks or global positioning sys- with your hands and count the number oftems to locate representative sample sites earthworms present. The smaller wormsthat can be relocated year after year. These found with the shovel will most likely besites become permanent locations for assess- the surface-dweller earthworms that do noting change over time. Each field site can be burrow vertically.marked on a map to aid relocation. At each Record the numbers on the assessmentsampling site, choose two points to take the sheet. Also note how easy or difficult it wasactual assessment. to shovel the soil. Turning a shovelful ATTRA Page 3
  4. 4. soil also correlates well with tilth and ease indicated here by a high score. Unstable of tillage. The more earthworms found in aggregates break apart easily and the this process, the better. Earthworm burrows individual soil particles can be easily eroded by enhance water infiltration and soil aeration. runoff water. Higher scores are generally more Earthworm digestion of soil and organic common under perennial sod. Lower scores are matter cycles nutrients. Worms are a general generally more common on soils with annual indicator of soil health. Earthworms may not tillage operations and clean cultivation. be present in croplands recently converted to Move away from the wire circle to a fresh pasture. They should slowly return over sev- area. Clip a small area of grass to ground level eral years from adjacent field margins as soil if necessary to see the soil surface clearly. Fill health improves. a 1-pint container with water. Holding the container as close to the soil surface as pos- 3) Soil smell sible, gently pour the water on the soil. Try While still at the hole dug for worm counts, to pour all the water out within five seconds, grab a handful of topsoil and take a whiff. the idea being to avoid disrupting the soil Record the smell on the assessment sheet as surface with the water flow, but pouring fast follows: enough to determine how quickly the waterA well- soaks into the ground. Using the stopwatch, aggregated 0.0 = putrid/chemical/sour start timing once all the water has been soil will take 0.2 = no smell poured out. Stop timing when the last of thein water rapidly, as water just finishes soaking into the ground. 0.4 = fresh/earthy/sweetwill a soil with high This is the infiltration time to be recordednumbers of vertical on the assessment sheet. 4) Aggregationwormholes. Next, measure the wet spot across its widest Select a soil aggregate, or crumb, from a hand- point with the tape measure and record the ful of topsoil. Make sure the aggregate is not length on the assessment sheet. Pouring on a a rock or pebble. Put the aggregate in the small slope will influence the rate of runoff. If you round bottle of water or the 1-pint container. are comparing two cropping practices on Allow it to stand for one minute, using the sloping ground, make sure the slope is the stopwatch to keep time. Observe if the aggre- same under both practices since slope will gate is breaking apart or staying intact. If it influence the runoff rate. stays intact after one minute, gently swirl the bottle several times and observe again. If it is still intact, swirl the bottle vigorously and 5) Water inf iltration observe the aggregate again for intactness. The faster water enters the soil, the less likely Record the following scores: it is to run off overland and cause erosion. A well-aggregated soil will take in water rap- 1 = aggregate broke apart within one minute idly, as will a soil with high numbers of ver- in standing water tical wormholes. Texture plays a significant 2 = aggregate remained intact in standing role in water infi ltration. Sandy soils will water but broke apart after gentle swirling take in water more quickly than silty-loam soils, and clay soils will take in water quite 3 = aggregate remained intact after gentle slowly. Finally, since soil moisture at the time swirling will influence this assessment, don’t put too 4 = aggregate remained intact after vigorous much confidence in an infiltration compari- swirling son between two fields if one is irrigated and the other is dry. After vigorous swirling, remove the aggregate and smash it between your fingers to make sure it was not a pebble. If it was a pebble, 6) Soil compaction select another aggregate and do the test again. Assessing soil compaction requires making a Healthy soils have very stable aggregates, simple tool beforehand. A soil penetrometerPage 4 ATTRA Assessing the Pasture Soil Resource
  5. 5. can be constructed from a 1/4-inch rod compaction of the surface layer, whichsharpened on the end as seen in Figure 1 restricts downward water movementbelow. Start with a rod that is 3 feet long. (Holistic Management International, 2007).Use a fi le to make 1-inch marks from thepointed end, as shown in the drawing. ConclusionPush your homemade penetrometer into the Performing the soil organism assessmentsoil as deep as you can with modest effort. described will enhance observational skills,Record the inches of penetration up to a max- which is always beneficial. Some other use-imum of 12 inches. Do not record any pene- ful observations include plant vigor, planttration depths beyond 12 inches, as we are not coloration, drought tolerance and the ratetesting for deep penetration. Avoid putting at which livestock manure is dispersed andall your weight into the pushing or stomp- decayed. Healthy soil conditions are largelying on the penetrometer to make it go deeper. created by the helpful soil organisms, whichRecord the penetrometer depth on the assess-ment sheet. If you hit a rock or tree root, try are beneficial with a little management toagain. For comparison, probe an undisturbed meet their needs.natural area nearby with your penetrometer. Don’t be discouraged if the pasture assess-As a secondary test, you may wish to probe ment numbers come up lower than expecteddeeper with a longer penetrometer to locate the first time. Rather, let the results be anany deeper hard pans to note on the comment incentive for continued commitment to soilsection of the assessment sheet. improvement. Pursue progress rather thanThe deeper the probe easily penetrates the perfection. An assessment provides a startingsoil, the better. Ease of soil penetration point from which to build toward the future.with the penetrometer correlates to deep Set your sights high. Discard the idea thatroot development, ease of downward water soils require hundreds of years to build up.flow, or no hardpan, and tillage ease. A Soils can begin to improve just a few monthsprobe that won’t penetrate the soil indicates after appropriate decisions are made.Figure 1: Homemade soil ATTRA Page 5
  6. 6. References Nation, Allan. 1995. Quality Pasture. Mississippi Valley Publishing, Corp., Jackson, MS. 285 p.Holistic Management International. Holistic Manage- To order this publication, visit the Stockman Grassment Biological Monitoring Manual. 2007. 59 p. Farmer online store at www.stockmangrassfarmer. net/cgi-bin/page.cgi?id=364.html or contact Stock- man Grass Farmer, PO Box 2300, Ridgeland, MSFurther resources 39158-9911, 1-800-748-9808, (601) 853-1861,Anon. 1999. Soil Quality Test Kit Guide. Soil QualityInstitute. Natural Resources Conservation Service. (601) 853-8087 FAX, sgf@stockmangrassfarmer.comUSDA. Accessed May 2009. Tugel, A.J., A.M. Lewandowski and D. Happe-vonArb,assessment/files/test_kit_complete.pdf eds. 2000. Soil Biology Primer. Ankeny, IA: Soil andAnon. 2003. Pastureland Soil Quality – Indicators Water Conservation Society. 48 p.for Assessment and Monitoring. Natural Resources To order this publication, visit the Soil and Water Con-Conservation Service. USDA. Accessed May 2009. servation Society online store at index.cfm?fuseaction=c_Products.viewProduct&catIEvanylo, Greg and Robert McGuinn. 2000. D=574&productID=5154Agricultural Management Practices And SoilQuality. Natural Resources and Environmental Holistic Management International. Holistic Manage-Management. Virginia Cooperative Extension. ment Biological Monitoring Manual. 2007. 59 p.Virginia Tech. Accessed May 2009. To order this publication, visit the HMI online at, Richard. No date. An Introduction to Nutrient or contact Holistic Management InternationalManagement. Conservation Technology Information Center. (HMI), 1010 Tijeras, NW, Albuquerque, NMAccessed May 2009. 87102, (505) 842-5252, (505) 843-7900 FAX,nutrient mgmt primer_1.pdf hmi@holisticmanagement.orgPage 6 ATTRA Assessing the Pasture Soil Resource
  7. 7. Pasture Soil Assessment SheetProperty________________________ Field _________________ Date _______ Examiner _________________ Living Soil Earthworm Earth- Aggrega- Water Water Points organism Soil smell penetra- holes worms tion infiltration infiltration types tion species/ circle #/circle #/shovel scorea scoreb timec distanced inches Site I 1 2 Site II 1 2 Site III 1 2 Totals Average*a smell score = 0 putrid/chemical/sour; 2 no smell; 4 fresh/earthy/sweet; for in-between smell, use odd numbers 1 or 3.b aggregation score – 1 = broke apart in water after 1 minute; 2 = broke apart after gentle swirling; 3 = intact after gentle swirling; 4 = intact after vigorous swirlingc time required for water to infiltrate into the soild distance across wet spot at widest point* divide the total in each column by 6Supporting Information1. Are there signs of erosion in this field? yes ____ no_____2. List the crops and practices done in this field in the last 2 years: _________________________________________________________________________________________________________________________________________________________________________________________________ ATTRA Page 7
  8. 8. Assessing the Pasture Soil Resource By Preston Sullivan, NCAT Agriculture Specialist Published 2001 Updated April 2010 by Hannah Sharp, NCAT Intern © NCAT Holly Michels, Editor Amy Smith, Production This publication is available on the Web at: or IP128 Slot 46 Version 042810Page 8 ATTRA