Loamy soilsLoamy soils have the most favorable physical properties
Potting media criteriaHigh moisture retention and rapid drainageIt can be difficult toeffective for both It is rarely cost optimizemoisturefarmers to change the texture retention and drainage in or other inherent properties ofreal soils the soils on their farms
≠Understanding inherent differences in soil properties
WEB SOIL SURVEY- a great source of info on soil inherent properties
What are these crazy peopletrying to do ? Location: Laurenburg, NC Date: 1961 Very deep plowing aspart of a futile effort to create deep “Prairie”soils in North Carolina
Good Tilth Poor Tilth The soil fabric http://www.grdc.com.au/growers/gc/gc48/conference1.htm
The soil pore network serves as a respiratory and circulatory systemhttp://www.mtm.kuleuven.ac.be/Research/NDT/IDO_SHerman_final.ppt
Understanding your soil’s respiratory and circulatory system Pore size Drainage pores 10- 30 μm Field Capacity Easily available Plant available water Permanent wilting point 0.2 μm Unavailable water Adapted from Buol (2000)
Relationship between fine mineral fraction and SOM Soils with more fine particles normally retain more SOM Magdoff and Weil (2004)
Weak relationship between clay content and SOC for 1261 agricultural soils in England and Wales Clearly many factors other than clay affect C accumulation Webb et al.(2003)
Temperature affects SOM dynamics Organic matter destruction by aerobic organisms Your farm and consumption in 50 yrs Organic matter Organic matter consumption OM production production synthesis by plants ~ 70 F mean annual temp TemperatureBrady and Weil (2002)
Landscape position affects SOM dynamicsPoorlydrained Where does the most OM accumulate? Interstream divide Somewhat Moderately LANDSCAPE poorly well drained drained POSITIONS Well drained Poorly Shoulder Interfluve drained Valley floor SOIL Backslope DRAINAGE CLASSES
Agriculture normally accelerates loss of SOM http://www.extension.umn.edu/distribution/cropsystems/components/7402_02.html
OM depleted top soilErosion has caused major redistribution of OM OM enriched sediment
Artificial drainage has greatly increased the number of days when soils are suitable for field operations but has also contributed Pollution of to manywater resources environmental Loss of SOM problems
4742 Identify 2 methods of increasing SOM. Adapted from Magdoff and Weil (2003)
Small increases in OM can improve macro-aggregation Superior air/water relationships Healthier root growth and function (justification statement)NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE
There’s more than one way to collect a soil sample but results have little value if the sample is not representative http://www.arlington.k12.va.us/schools/abingdon/programs/naturalistclub/pic%2012-04/good%20diggin%20shot.JPG
Composite samplingMultiple sub-samples arecollected fromeach managementunit and mixedtogether
Recommendations Analytical results So what do thenumbers mean ???
Have any of you ever had to run a 40as part of a try-out for a team? How well does an athlete’s 40 time predict their ability to play the game?
By themselves, extractable nutrient levels are not informative. Extractable nutrient levels provide an index ofnutrient availability that can be interpreted using results from field experiments.
Meaningful interpretation of soil test results requires field calibration100 %yield 50 % yield Soil test P concentration (ppm) http://www.ipm.iastate.edu/ipm/icm/2003/11-17-2003/mehlich3.gif
moisture temperature microbial activitySoil test levels are not directly related to most of the factors controlling nutrient availability during a growing season. Calibration experiments were not conducted using organic management practices rooting depth root health
http://www.extension.umn.edu/distribution/horticulture/components/M1190fig1.htmNutrients that are not Nutrients that can be easily redistributed easily redistributed
Sampling vegetable crops for tissue analysis http://www.cahe.nmsu.edu/pubs/_a/a-123.html
Analytical results Estimated Nutrients available for a single cropTotal nutrient content of DM is adjusted for moisture and availability http://188.8.131.52/D:/2005/WASTES/Predicti/7000/WAW06343.PDF
Feed the soil vs. Feed the crop ? Both strategies are important ! Unhealthy roots in soils with low SOM and poor structure use nutrients inefficiently… Healthy roots need available nutrients !Plants with poorly developed roots tend to havenutrient deficiency Acute rootand drought stress disease symptoms Chronic root malfunction
How oftendo you How oftenlook atlook do youroots ? at roots?
What happened to my soil?? Tillage when a soil is too wet often creates clods that require a period of wetting and drying and/or freezing and thawing (in addition to biological activity) before good structure is restored.
Are you familiar with the fence post principle? Zone of maximum biological activity and rapid residue decay
The soil stomach Bacteria Plant roots depend Fungi Microflora on an external Algae digestive system Protozoa Microfauna “ the soil food web” Nematodes Microarthropods Mesofauna Enchytraeids Earthworms Ants, termites, spiders Macrofauna Mollusks Others: rodents, snakes, Megafauna voles, amphibians, etc.
What do bacteria do in soil ? Colonize aerobic and anaerobic environments Decompose easily digested organics Mediate redox transformations Nourish bacterivores Fix N
Most N transformations in soil are carried out by bacteria!! SoilPlant biomass
What do fungi do in soil ? Decompose less easily digested organics Penetrate residues Stabilize soil structure Nourish fungivores Form symbioses with plant roots and soil fauna Compete with plant pathogens Parasitize plants and soil animals Produce toxins e.g. aflatoxin produced by Aspergillus flavus on peanut
Most plant pathogens arefungi but most fungi are not plant pathogens !!
Soil organisms in areconcentrated HOT SPOTS ! detritusphere rhizosphere Adapted from Coleman et al. (19??)
Cover crops increase annual root production and function Feed livestock Cover Crops Recent studies indicate thatCCs can have many root production is the bestother beneficial predictor of long-termeffects Adapted from Magdoff and Weil (2004) retention of SOM.