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Soil Quality and Organic Farming: 

Soil Quality and Organic Farming HORT 390 Fall 2006

Soil is more than nitrogen (N) phosphorus (P) and potassium (K): 

Soil is more than nitrogen (N) phosphorus (P) and potassium (K)

Nitrogen deficiency symptoms (poor growth, yellow OLDER leaves): 

Nitrogen deficiency symptoms (poor growth, yellow OLDER leaves) Tomato: Growth dwarfed, thin and upright habit; stem and petioles rigid; leaves pale green, occasional purplish tints, older leaves yellowing. from The Diagnosis of Mineral Deficiencies in Plants by Visual Symptoms by Thomas Wallace, M.C., D.Sc., A.I.C. Published by His Majesty's Stationary Office — 1943 Carrot: Growth dwarfed and thin; leaves pale green and older leaves yellow and red tints and die off early. Celery Plant: Growth dwarfed; foliage pale green and older leaves yellow and die early.

Phosphorus deficiency symptoms (poor root growth, purple color): 

Phosphorus deficiency symptoms (poor root growth, purple color) from The Diagnosis of Mineral Deficiencies in Plants by Visual Symptoms by Thomas Wallace, M.C., D.Sc., A.I.C. Published by His Majesty's Stationary Office — 1943 Growth stunted; leaves lustreless green and dull purple tints. Leaves strong purple tints. Growth dwarfed and thin; leaflets droop, curl backward and develop strong, dull purple tints.

Potassium deficiency (burning at leaf edges, don’t confuse with insect damage): 

Potassium deficiency (burning at leaf edges, don’t confuse with insect damage) Leaflets slight marginal and intervenal chlorosis followed by brown marginal scorching; scorched margins curled foward. Intervenal chlorosis near margins followed by marginal scorch. Internodes short, leaves relatively long; marginal and tip browning of leaves.

Slide6: 

Prairie Soil vs. “Ag” Soil N and P in the organic matter pools.

Fertility Amendment Options- Nitrogen (N): 

Fertility Amendment Options- Nitrogen (N) Organic Sources Cow manure .5-1.5% Horse manure 0.6 % Chicken manure 2-4% Sheep 3-4% Alfalfa hay 2.5 % Blood meal 13% Soybean meal 7% Fish meal 10% Vetch 3.1% Compost 1-3% Fertilizers Ammonium nitrate 33% Anhydrous ammonia 82% Ammonium sulfate 21% Potassium nitrate 13% Urea 46%

Fertility Amendment Options- Phosphorus (P2O5): 

Fertility Amendment Options- Phosphorus (P2O5) Organic Sources Cow manure .7-1.6% Horse manure .7-1.2 % Chicken manure 4.5-6.0% Sheep 1.2-1.6 Alfalfa hay 0.5 % Blood meal 2% Soybean meal 1.2% Fish meal 6% Vetch 3.1% Bone meal 15% Compost 0.5-1.5% Fertilizers Phosphoric acid 54% Superphosphate 20% Concentrated superphosphate 46% Rock phosphate 30% (but availability very low) Colloidal phosphate 22% (availability low, but better than rock) Note: Rock and colloidal sources allowed in organic production.

Fertility Amendment Options- Potassium (K20) : 

Fertility Amendment Options- Potassium (K20) Organic Sources Cow manure 2.4-3.6% Horse manure 1.2-2.2 % Chicken manure 1.2-2.4% Sheep 3-4% Alfalfa hay 2.5 % Blood meal 1% Soybean meal 1.5% Vetch 2.5% Wood ash 5-7% Greensand 5% (low availability) Compost 0.5-2 % Fertilizers Potassium nitrate 44% Potassium chloride 62% Potassium sulfate 53% (allowed in organic production if mined and not refined)

Fertility Amendment Options- Pros and Cons : 

Fertility Amendment Options- Pros and Cons Organic Sources Can be bulky, best if locally available. Sometimes less expensive, sometimes more expensive Most contribute to organic matter pool and long-term fertility Must wait at least 90 to 120 after “raw” manure application to harvest food crops. Fertilizers Convenient, available for purchase. Soluble, plant available Many contribute to the “salt index” of the soil, and also most lower the pH (see Knott’s handbook for details)

Slide11: 

Organic Matter Pool, or “Savings Account” Available Nutrient Pool, or “Checking Account” Extractable N, P, K, pH and micro-nutrients -- Organic matter -- Total N & P -- Total C & N

Slide12: 

“Banking” on Soil Nutrient Levels Your Checking Account -- Mineral N, available P and K -- This is an indication of what will be available that growing season -- Soil pH will influence the availability of these and micro-nutrients Your Savings Account -- Organic matter content, total N, total P, clay release of K. -- These are slowly available, but can accumulate over time to be available later. -- This is sometimes called nutrient “buffering.”

Slide13: 

How to build up your soil “savings” account. Local, on-farm sources: - cover crops, annuals and perennials. - hay mulch - compost - raw manure (use with caution, not on leafy crops) - wood chips, ash (also use with care) Purchased products: - alfalfa and soybean meal (N) - bone meal, rock phosphate (P) - lime (for pH) - sulfur (to lower pH) - blood meal (for N)

Slide14: 

Practices that deplete your soil “savings” account. Too much tillage. Bare ground (no mulch on top). No living crops (no roots in the soil). Soluble fertilizers without concurrent addition of carbon rich mulches or composts.

Slide15: 

Definition of Soil Quality Soil Fertility Physical Properties Biological Activity “The ability of soil to function; to supply plants with adequate nutrients, have good drainage and aeration, promote root growth and biological activity.”

Slide16: 

Soil is not Dirt

Physical Tests -- Soil Texture: 

Physical Tests -- Soil Texture Fill a jar 2/3 with soil. Fill the same jar about 7/8 full of water. Add detergent (optional) to break up aggregates. Shake well. Measure height of settling at 30 seconds, 30 minutes, and 24 hours – or -- look at particle size differences – sand, silt, and clay layers.

Texture largely determined by parent material of soil, past erosion, and new deposits (such as topsoil addition): 

Texture largely determined by parent material of soil, past erosion, and new deposits (such as topsoil addition) Sandy soil – good drainage, but doesn’t hold water or nutrients well. (particles 0.05 to 2 mm) Silt – moderate drainage, moderate nutrient and water holding capacity. (0.002 – 0.05 mm) Clay – poor drainage, can supply K mineral, shrink/swell with water (<0.002 mm) All of these characteristics are helped with the addition of organic matter, especially composts.

Can also examine “macro-organic matter flotation” with the same system.: 

Composts Grass sod Various garden plots Ag field with no residue Macro-organic matter is important because it feeds the “active” organic matter pool, that promotes water stable aggregates, infiltration, and other positive soil attributes. Can also examine “macro-organic matter flotation” with the same system.

Organic Matter Pools: 

Organic Matter Pools Stable Humus Macro-Organic Matter (mulch, residue, roots, large pieces of compost, etc.) Active Decomposing Organic Matter (particulate OM or POM) Soil Test for OM Active OM Stable OM Humus test

Soil biological tests include earthworm counts (by hand), extraction of soil insects with light above and funnel below into a jar. No accurate tests yet for microbial species diversity. Soil respiration rate tests also available, but difficult to interpret.: 

Soil biological tests include earthworm counts (by hand), extraction of soil insects with light above and funnel below into a jar. No accurate tests yet for microbial species diversity. Soil respiration rate tests also available, but difficult to interpret. Soil Biology

Soil biological test interpretation: 

Soil biological test interpretation The “let it rot” test More soil biological activity results in faster rate of decomposition of cellulose material (paper, cloth, wood, etc.) In general, soil microbial diversity and abundance is a good thing. Detailed fungal and bacterial counts can be performed by professional labs, but the results may not be very repeatable. Also expensive.

The “will it rot?” soil test.: 

The “will it rot?” soil test. Wet filter paper. Place in bottom of flat covered dish. Fill dish with moist soil. Add a little more water if needed. Incubate and watch. Observe the amount of decomposition after certain length of time. Examples (see photos) incubated for 1 week at 95o F. Worm compost Garden soil Field soil

Soil Respiration Rate –the reality: 

Soil Respiration Rate –the reality More CO2 (carbon dioxide) coming off the soil means the soil is respiring (breathing) more. This indicates either a high rate of respiration of existing organisms, or high numbers, or both. Having more organisms is a good thing, but a high respiration rate also means your soil system is burning off carbon…which lowers your organic matter levels, which is a bad thing. High respiration rate is a result of optimal temperatures, moisture, and aeration, sometimes as a result of tillage.

Water Stable Aggregates: 

Water Stable Aggregates Formed by the aggregation of clay (smallest particles), followed by gluing together of macro-aggregates with bacterial secretions, fungal hyphae, and root hair bonding.

To measure water stable aggregates:: 

To measure water stable aggregates: Use a stack of sieves under water. Demonstrate with a few aggregates in a shallow dish. Field soil Prairie soil

To measure the effect of water stable aggregates:: 

To measure the effect of water stable aggregates:

Procedure:: 

Procedure: Assemble filter paper, funnel, and jar. Add 1 scoop (dry) soil. Gently add 1 scoop water and start timer. Record first reading when water is not visible. Repeat with 2nd scoop of water.

A similar test can be run in the field. Use a section of irrigation pipe or coffee can to create an “infiltrometer.”: 

Figure 14. Illustration of an infiltrometer A similar test can be run in the field. Use a section of irrigation pipe or coffee can to create an “infiltrometer.” In a 6 inch diameter ring, pour 1 7/8 cup water. Measure amount of time to soak in. Repeat measurement.

Four Ways to Improve Infiltration:: 

Four Ways to Improve Infiltration: Add organic matter Add organic matter Add organic matter Don’t work the soil when wet!!!

What to do with results from the Soil Test Lab: 

What to do with results from the Soil Test Lab

Slide32: 

Collect sample Lab does something with it….. Results and recommendations sent to you in the mail. Put on some fertilizer or other product

Soil Tests – the art and the science: 

Soil Tests – the art and the science Recommendations for fertility amendments Action Representative sample collection Lab accuracy, differences of methods. Interpretation of the lab values – low, medium, high, very high…. Previous crop Intended crop Cropping history and legume credits Manure and compost credits Late spring nitrate test Organic matter levels sample handling, drying….

Idealized fertilizer response curve: 

Idealized fertilizer response curve Fertilizer rate Yield Low High

Nutrient levels – a story about Goldilocks and the three bears…..: 

Nutrient levels – a story about Goldilocks and the three bears…..

Slide36: 

Hypoxia - The dead zone, a 6,000-square-mile area in the Gulf of Mexico that is almost totally devoid of life, persists despite conservationists’ ongoing efforts to rein it in. First mapped in the mid-1980s, the zone is caused by nitrogen fertilizer runoff, which flows from inland farms down the Mississippi River and into the gulf. Nitrogen causes huge summer algal blooms that decompose and sink to the bottom, where bacteria feast on them and, in the process, suck vital oxygen from the seawater. Courtesy of SEAWiFS/NASA/ GSFC/Orbimage   Brownish water from the Mississippi River billows into the Gulf of Mexico in this 2000 image.

Interpretation of chemical tests: 

Interpretation of chemical tests How much is “just right?” How do you know if there is not enough? When is there too much?

Several options for fertilizer recommendations include:: 

Several options for fertilizer recommendations include: Replacement – calculate anticipated needs of crop (in lb/A) and apply that level (minus soil test level). Allow for fertilizer use efficiency of only 50%, and also 25 to 50% from organic sources in application year. Sufficiency – based on previous research, estimate average fertilizer amount to achieve 90 to 95% of maximum yield. Little consideration of future nutrient levels. Build-maintenance – attempt to minimize the probability of P or K limiting crop yield, and also build soil test levels over a 4 to 8 year period. FBTSOYP – common method, observe plants, and track soil test levels periodically.

Ways to detect nutrient deficiencies: 

Ways to detect nutrient deficiencies Visual symptoms; use your crop as a bioassay. This could be costly if levels are too low. Tissue testing. This more common with perennial crops, large scale cropping. Requires standardized controls with known developmental age/stage, certain plant part (e.g. “petiole of the 4th leaf from the growing tip,” Soil test; Promoted for years, practiced by some.

When looking at plant symptoms, remember that:: 

When looking at plant symptoms, remember that: Symptoms indicate lack of plant availability or uptake of the nutrient. This could be due to low levels in the soil, OR…. Root system of the plant is stunted. This could be due to soil compaction, poor aeration/flooding, not enough irrigation, or other reason. Look at the roots. Blossom end rot in tomatoes in KS often occurs with the first fruit, before the roots are fully developed. (Marr, pers. comm.) Mycorhizae can improve root function.

Understanding pH: 

Understanding pH (chart of nutr. Avail. Here)

How to adjust soil pH: 

How to adjust soil pH Add liming products to raise pH. See various sources in publications. Not commonly needed in KS unless using fertilizers that acidify the soil. Add sulfur to lower pH. Ammonium sulfate works fastest, but elemental sulfur allowed by organic standards. See sheets for rates. Soils with high exchange capacity (CEC) will require more product to change the pH.

Slide43: 

Summary --A Definition of Soil Quality – Context: soil type, slope, climate……. Problems -Salinity -Low in nutrients -Erosion -Drainage Soil is OK Soil Quality - High OM - Tilth - Infiltration Nutrient buffering

For more information:: 

For more information: http://www.oznet.ksu.edu/ (to get to all KSU publications, soil test lab info, etc.) http://www.oznet.ksu.edu/kswater (for “Citizens Guide to Soil and Water Testing”) http://soils.usda.gov/sqi/index.html (fact sheets and other info on soil quality) http://www.woodsend.org/ (copies of other soil quality publications, compost testing) http://www.amazon.com or other book seller (for copies of “Soul of the Soil.”)

Product Related Web Sites:: 

Product Related Web Sites: http://www.woodsend.org/ (compost testing, respiration rate tests) http://www.lamotte.com (for nutrient and humus test kits) http://www.hach.com (for nitrate, pH, and ammonia test strips) http://www.3m.com (for E. coli plates, order #6484 EC plates, $70 for 50, also need pipets)