Maximizing Soil Health in Organic Systems

1. Organic Soil Management Primary importance in organic systems Organic systems depend on soil organisms to supply nutrients and suppress disease. Purpose of management is to nourish soil organisms so they can build soil structure and cycle nutrients.

2. Factors to be managed • Soil air Greatest • Soil water • Soil organic matter • Soil minerals Least Plant response

3. Soil air management • Most important because beneficial soil organisms need oxygen to live. • Anaerobic organisms produce plant toxins and bad smells. • Plants also need oxygen in the soil for nutrient uptake and for growth of the roots. O2

4. Typical oxygen and Carbon dioxide levels in soil and air Oxygen 21% Carbon dioxide 0.0376% Oxygen 15% Carbon dioxide 2-4%

5. Gas exchange needed to replenish oxygen in soil • Factors which drive gas exchange: • Temperature • Rainfall or irrigation • Gas diffusion • Barometric pressure

6. Temperature • Gas particles move away from each other as temperature rises – less dense. • As temperature in soil increases, the gas with high carbon dioxide concentration to move to atmosphere. • As temperature in soil decreases, it causes atmospheric, oxygen rich gas to move into soil. Soil Temp. Carbon dioxide Soil Temp. Oxygen

7. Rainfall or Irrigation • Water occupies same space in soil as air. • As water fills the space, it drives out the air. • As water drains through the soil, it draws air in behind. • Wet soil heats and cools more slowly than dry soil.

8. Gas diffusion Gases move from areas of higher concentration to areas of lower concentration Low High CO2 High O2 Low Oxygen 21% Carbon dioxide 0.0376% Oxygen 15% Carbon dioxide 2-4%

9. Barometric pressure • Effects on soil air just as atmospheric air – high pressure pushes oxygen rich atmospheric air into soil • Low pressure causes carbon dioxide rich soil air to escape to the atmosphere • Soil air is slower to respond than atmospheric air

10. Managing Soil Air • Primary management technique is tillage • Breaks up soil to ped size- good gas exchange • Avoid compaction • Compaction limits pore space • Avoid crusting • Raindrops destroy soil structure, limits gas exchange

11. Soil Water Management • All living organisms need water to survive. • Too much or too little water can kill.

12. Properties of water • Polar molecule • Universal solvent • Surface tension • Capillary action • Cohesion Courtesy of rst.gsfc.nasa.gov

13. Soil water capture and retrieval • Cohesion –water molecules are attracted to each other and pull each other along • Saturation • Field capacity • Capillary action

14. Managing soil water • Primary technique is tillage – to create pore space • Optimum soil water content is 20-30% but it will fluctuate with rain and/or irrigation • Monitor soil moisture with moisture meter or visual examination • Different areas will have different moisture levels

15. Soil organic matter • Made up of living and dead residues in different stages of decomposition (living, dead and long dead) • Food source for the decomposers who feed on dead organisms and waste products

16. Soil organic matter • Living • Bacteria decompose simple carbohydrates • Fungi decompose complex organic materials • Recently dead • Micro- and macro- organisms – plant roots, earthworms, fungi, bacteria, etc. • Long dead • Well decomposed humus • Holds nutrients and water in soil • Dark color causes to warm up faster

17. Factors which effect soil organic matter • Climate – temperature, rainfall • Soil texture –heavy clay vs light sands • Topography- steep, flat slopes • Vegetation – grasslands , forest • Soil pH – neutral, acidic or basic • Cultural factors – tillage, crops, soil amendments

18. Managing soil organic matter • Two ways: • Conserve existing organic matter • Adding organic matter to soil

19. Conserving soil organic matter • Avoid excess tillage • Retain crop residue • Cover crops

20. Adding organic matter to soil • Raw manure • Organic standards considerations • 120 days for root crops • 90 days for other crops • Compost • Requires a large amount • Must have source of materials to compost • Must be gathered

21. Soil mineral management • Least effect on crop production • Good management leads to better plant health, higher nutritional quality, increasedflavor and shelf life • Especially important in SE US because soils have been depleted – long warm season with abundant rain – higher rates of reactions in the soil, rapidly leached out of soil N P K S Ca Mg Fe Cu

22. Essential soil minerals

23. Managing soil minerals • Primary technique is a soil test • Analysis of test • How to Convert an Inorganic • Fertility Recommendation to an Organic One

24. Tillage and cultivation • Tillage • Deeper • Purpose to incorporate air space • Cultivation • Shallower, less than 1 inch • Purpose to improve aeration and combat weeds

25. Tillage • Incorporate air spaces • Avoid mixing layers • Use only when necessary • Timing depends on soil type • Clay soils- not too wet or too dry • Sandy soils – must have high moisture

26. Farm implements Chisel plow Tiller Spader Subsoiler

27. Double digging • Double digging is a type of tillage, done by hand. • The purpose is to loosen the soil so that water and roots can penetrate deeply. • Equipment needed is a shovel, sturdy fork, board, marking string or tape, stakes and tape measure. • The other vital component is strength and energy!

28. Select a site in full sun

29. Clean off the vegetation

30. Measure off the bed

31. Mark the bed perimeter

32. Dig a trench across one end

33. Put the soil in a wheelbarrow

34. The trench should be a spade length in depth

35. Use a board to stand on while digging, to reduce compaction

36. Use a fork to loosen soil below trench

37. Dig another trench, filling in the first with soil from the second trench

38. Use the fork to loosen the soil in the second trench

39. Double digging • Continue to dig trenches, filling in the previous ones, until the whole bed is dug. • Use the soil from the first trench to fill in the last trench dug. • This may take a while, depending on how hard your soil is and how many people are working. This bed is going to take a while, since the clay is really hard. • Thanks fo Chuck Pugh and Silford for the demonstration.

40. Summary • Purpose of management is to nourish soil organisms so they can build soil structure and cycle nutrients. • Soil air – most important, managed with tillage • Soil water – dipolar nature results in special characteristics, occupies same space as air • Soil organic matter –material from which bacteria and fungi release nutrients • Soil mineral – 12 essential minerals, managed with soil test