Building Soil Organically: A Discussion of Practical Applications and Why They Work

Bo HollandScreech Owl FarmNelson County, VA

Daniel ParsonOxford College Farm

Oxford, GA

Approach to Production

• Diverse vegetable operation• About 3 acres production• Intensive rotation in 12 quarter-acre blocks• Marketing-CSA, Farmers’ Market, Restaurant

sales

Organic Production

“A production system that is managed… to respond to site-specific conditions by

integrating cultural, biological, and mechanical practices that foster cycling

of resources, promote ecological balance, and conserve biodiversity”

Organic Fertility

• Cultural: Rotation planning• Mechanical: Mined substances• Biological– Cover cropping in rotations– Plant and animal materials

Crop Rotations

• Prevent one crop from robbing nutrients• Allow maximum use of cover crops• Provide planning for fertility– Crop list applies directly to land area– You know what crop comes next– Possible to schedule liming or compost/mulch

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Converting a Conventional Recommendation to Organic

• UGA online resource• Apply organic amendments for any

recommendation• What is your preferred amendment?– Least expensive– Most effective– Locally available– On-farm resource like compost

Converting a Conventional Recommendation to Organic

• Begin with your preferred amendment-or-

• The most balanced in N P K• Determine what else you need to apply• Convert amendment pounds/acre to

pounds/field or pounds/bed

What Next?

• Calculate application for each field• Chart the amounts for each amendment• Add up those amounts• Put together an order– Plan ahead for when you need the materials– Get together with others in your local area

Make it Practical

• Write down ‘recipe’ for each field• Make copies and keep in the barn• Convert to volume on fertilizing day– Weigh amendments into bucket/container– Mark bucket or container– Use markings each time to get it right

• Load bags into cart and measure in field

Is it Effective?

• Previous ‘one-size-fits-all’ approach– Wasting $ and resources?– Optimal crop response?

• New system for 2013– Spent the same $ on amendments– Improved crop response– Better use of resources

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Building Soil Organically: Practical Applications and Why they Work

Southern Sustainable Agriculture Working Group Annual Conference

Mobile, AL – January 17, 2014

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Principle: Feed the Soil, and Let the Soil Feed the Crop

• Soil life modulates the release of plant-available nutrients.

• Its activity is intensified in the plant rhizosphere (next to root surfaces) to maximize efficient nutrient delivery.

Provided that the soil life receives an adequate quantity and diversity of organic residues and plant root exudates.

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Why it Works: Strengths of the Parson Produce Cropping System

• 18 cover crops within a 13 year crop rotation.

• Most cover crops grown to early flowering = optimum stage for quality and quantity of fresh OM.

• Organic fertilizers (feather meal, True 7.5-5-7.5) also feed soil life.

A vigorous cover crop of buckwheat occupies a fallow bed (foreground).Production crops grow in other beds (background).

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Why it Works: some Enhancements to Consider

Add compost to the system: Provides diverse inoculum

of beneficial soil organisms. Good source of P –

calibrate rate to deliver desired amount.

Shorten interval between cover crop termination and vegetable planting: Consider no-till or strip-till

planting into rolled cover.

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Principle: the Law of ReturnGive back to the soil what has been taken out through production and cultivation.(Sir Albert Howard, 1940s)

Nutrients: replenish nutrients removed in harvest

Organic Matter: feed the soil life – cover crops, manure, organic mulch, residues, etc.

Harvest removes nutrients and organic matter from the cycle. Tillage burnsup OM, promotes leaching.

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Why it Works: Strengths of the System

• Science-based translation of Clemson U. recommendations for organic fertilizer use.

• Clemson U. rates for N and K are conservative, and thus sufficient.

• Crop- and field-specific NPK rates optimize outcomes.

• Slow-release organic fertilizers can be applied pre-plant – no side-dress needed.

Tomatoes may require more K and less N than leafy greens, and are amended accordingly.

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Why it Works: some Enhancements to Consider

Legume or legume-grass cover crops can provide 35-100 lb available N/ac.

Nitrogen recommendations ignore soil mineralization and cover crops: Can reduce N inputs by 0.5X

the total cover crop N. Healthy, living soil can

provide most or all of a warm season crop’s N needs.

Cool season crops need additional N – succulent green manures or organic fertilizer.

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Why it Works:some Enhancements to Consider

Clemson U. recommendations for P exceed crop P removal even where P tests sufficient. Vegetable harvests remove

20 – 60 lb phosphate/ac. Reduce phosphate

application to this range except where soil P is below sufficiency.

Very high soil P inhibits mycorrhzal fungi – apply less P for net drawdown.

Phosphorus application rate

In low-OM, low-biological activity soil, much of applied P is tied up, and rates higher than actual crop uptake areneeded for optimum economicyield. In healthy, living soil, mycorrhizae and other soillife make more P crop-available.

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A couple concerns with the Clemson recommendations

• Micronutrient recommendations based on crop only, without reference to soil test level:– Manganese recommended for snap bean (“Mn-

sensitive crop”) where soil Mn level is ample. – No Mn is needed in this case.

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Four Principles of Soil Health

• Keep soil covered as much of year as possible.• Maximize living roots in the soil profile.• Minimize soil disturbance.• Energize the soil system with biodiversity.– Multi-species cover crops - 5 or more species from

3 or more plant families

Based on the work of the NRCS Soil Health Team in Greensboro, NC – David Lamm, Ray Archuleta, Steve Woodruff, and Terry Briscoe

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Why it Works: Strengths of the System- maximizing soil coverage, living roots

• Tight Rotation – 18 cover and 18 cash crops in 13 years

• No unplanted fallow• Living vegetation

present most of the year

• Cover crops provide abundant root exudates for soil life

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Why it Works: Strengths of the System- minimizing soil disturbance

• No chemical pesticides, herbicides, fungicides – protects soil life.

• Limited use of soluble fertilizer (potassium sulfate only).

• Minimal, shallow tillage to plant cover crops after vegetable harvest.

Cover crops, cash crops, and even weeds are far better for the soil than herbicide-fallow.

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Why it Works: some Enhancements to increase cover & roots, reduce disturbance

• Reduce tillage and waiting period after cover crop.

• No-till cover crop roll-down and vegetable planting.

• Practical for tomato, pepper, broccoli, cabbage, other transplants, potato, garlic, squash, beans.

• Possibly cucumber, melon.• Not suitable for beets, carrots,

direct-sown greens spading machine for one-pass cover crop tilldown.

Pepper starts are no-till trans-planted by machine into aroll-crimped cover crop of wheat at North Carolina A&TState University, Greensboro.

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Practical considerations: green manure cover cropping

Pros: Readily-available food for soil life Maximizes active organic matter Biofumigation (brassica covers) Fine seedbed for direct-sowing Accelerates nutrient release

Cons: Tillage burns up SOM, disrupts

soil fungi & earthworms May lead to crusting, erosion Stimulates weed emergence

Plow-down vetch green manure feeds soil life,releases N, facilitatesseed bed preparation.

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Practical considerations: roll-crimping

The roller-crimper terminates mature annual cover cropslike this without tillage or herbicides.

Pros:Maximizes stable and total

organic matter.Continuous soil coverage.Reduces emergence of annual

weed seedlings. Soil fungi, earthworms

undisturbed.

Cons: Slower nutrient release. Lower soil temperature.Cannot direct-sow fine seeds.Perennial weeds may increase.

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Why it Works: Strengths of the System- energizing with diversity

• 20 vegetable crops from 11 plant families.

• Cut flowers in rotation add more diversity.

• 9 cover crops from 3 plant families.

• Each crop fosters a unique soil microbiota in its rhizosphere.

Diversified crop rotations support a wider diversity of life below ground, thereby enhancing soil fertility and soil quality.

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Why it Works: Enhancements to consider to increase diversity

• NRCS soil health teams in Greensboro, NC and in North Dakota are planting cover crop mixes of 5 – 10 species from 3 – 5 families.

• Increased benefits to soil quality and cash crop yield are seen compared to grass-legume biculture.

Some examples: Rye, oats, hairy vetch, crimson

clover, Austrian pea (winter – commercially available)

Rye, wheat, oats, tillage radish, Aus. pea, crimson clover, vetch, turnip, mustard (winter – NRCS trials in VA)

Sorghum-sudan, pearl millet, cowpea, buckwheat, sunflower (summer – used in home garden)

Building Soil Organically: A Discussion of Practical Applications and Why They Work

Bo HollandScreech Owl FarmNelson County, VA

Daniel ParsonOxford College Farm

Oxford, GA