Kefyalew Girma DestaOklahoma Cooperative Extension Service

Plant and Soil Sciences Department

Organic Matter MATTERS!

IT MEANS A LOT! Improve water infiltration rate/holding capacity Supply free nutrients Decrease pests, pollution from pesticides and

heavy metals Soil pH buffer Improve soil tilth/ structure Reservoir of nutrients and water CEC C sequestration: reduce CO2 and CH4

Improve microbial mass and species diversity

OM level %

WHC, lbs Rain ,in

4-5 165-195 4-6

1.5-2 35-45 0.5-1.5

If OM<2.5%, N,P and K leach away

Water holding capacity

NT vs CT

Prior et al., 2003

Mielniczuk, 1996

pH

Infiltration

. . . IT MEANS A LOT!

Effect on CEC

Soil particle CEC (cmol/kg)

Humus 100-300Smectites (black swelling clays)

60-150

Kaolinite (white clay) 2-15

Fe and Al oxides (from ferrosols)

<1

McLaren and Cameron (1996).

Gardener et al.,2002; composting and compost proceeding

Effect on microbes, dairy manure

First thing first! What is the goal?

o Short-term nutrient supply o Slow nutrient supply

Highly decomposable material vs slow decomposing materials

Nature of the organic enterprise Soil type and problem

Building Soil OM 3-Strategies

1. Decrease losses

2. Add Organic Material/Matter

3. Consider Sustainability

1. Building Soil OM: decrease losses

Reduce tillage Erosion control

Corn, Hussain et al., 1999, SSSAJSchertz et al., 1984, ASAE, proceeding

. . . Decrease lossesMinimize monocropping

Crop Sequence Inches of topsoil remaining

Continuous Corn   7.76-year rotation* 12.2Continuous timothy grass

17.4

* Corn, oats, wheat, clover, timothy, timothy, 100 yrs Gantzer et al. 1991, AJ 83:74-77

Highly Variable

1. Cover Crops Spring Annuals

o Oats and Triticale.

Summer Annualso Buckwheat, Cowpea, and Sorghum

Winter Annualso Austrian Winter Pea, Hairy Vetch and Winter Rye

are planted in late summer/early fall, over winter, and resume growing the following spring.

Biennials:o Yellow Blossom Sweet clover and perennials Red

Clover can be grown for longer term soil-building.

. . . Cover CropsCommon C:N ratios of cover crops

Organic Material C:N Ratio Reference

Young rye plants 14:1 (Sarrantonio, 1994)

Rye at flowering 20:1 (Sarrantonio, 1994)

Hairy vetch 10:1 to 15:1 (Sullivan, 1990)

Crimson clover 15:1 (McLeod, 1982)

Corn stalks 60:1 (Sarrantonio, 1994)

Sawdust 250:1 ((McLeod, 1982)

If we return 2.2 tons/ac/yr of residue to the soil, it will maintain soil OM at constant level in continuously cropped soils.

2. Green manure

Non-legumes: supply OM Legumes

o Both OM and fix No Legumes add 25-70 lbs N/ac

. . . Green ManuresBiomass and N yields of winter annual GM crops

Cover Crop Biomass tons/acre Nitrogen lbs/acre

Sweet Clover 1.75 120

Berseem clover 1.10 70

Crimson Clover 1.40 100

Hairy Vetch 1.75 110

“Green manure crops can supply an OM equivalent of 9 to 13 tons per acre of farmyard manure or 1.8 to 2.2 tons dry matter per acre.” However, the benefit from green manure crops’ soil benefits will be gone in a year or less.

Schmid and Klay, 1984

3. Animal Manure

Type N, lbs/t

P, lbs/t K, lbs/t Solids%

% PAN yr1

B density lbs/cu yard

Dairy solids 5 1 2 20 0-20 1100Beef feedlot 12 3 14 25 20-40 1400Broiler litter 73 28 55 70 40-70 900Laying hen 37 25 39 40 1400Horse 9 3 13 35 0-20 1400Sheep 18 4.0 29 28 1400

Species, feed, and handling dependent

4. Compost Low in nutrient Low availability More of OM buildup Very easy procedures available Any organic material can be composted Materials vary

Compost vs Manure?Compost Manure

slow release form of nutrients usually higher nutrient content

easier to spread sometimes difficult to spread

higher investment of time or money lower investment of time or money

lower potential to degrade water quality

higher potential to degrade water quality

less likely to contain weed seeds more likely to contain weed seeds

reduced pathogen levels potential for higher pathogen levels

more expensive to purchase less expensive to purchase

fewer odors odors sometimes a problem

improves soil tilth improves soil tilth

5. Uncomposted Yard Debris Nutrient rich/poor, depends on

material Better than compost Grass clippings release nutrients

quickly; 20 lbs N/wet ton, 5-20% is available

Wood takes for ever! Leaves and small branches

decompose quickly

6. Packaged Organic Fertilizers Easy to use Less variable More concentrated Expensive! Blended forms

Organic Fert N, (%DW)

P2O5, (%DW) K2O (%DW)

Feather meal 1-2 1-3

Steamed bone meal 7-13 20-30 <1

Dried Kelp 1-2 <1 2-15

Seed meal 6-7 2-3 1-2

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