SOIL QUALITY- AGRONOMY Technical Note No.1

Cover and Green Manure Crop Benefits to Soil Quality

Soil Quality and Resource Effects of Conservation Practices Management One of the goals of conservation Soil is one of the five resources— planning is to consider the effects of soil, water, air, plants, and animals—that conservation practices and systems on NRCS deals with in resource planning. soil quality. This is the first technical Soil is intimately related to the other note in a series on how conservation four resources, and its condition can practices affect soil quality. This either negatively or positively impact the technical note is designed to compliment United States other resources. For example, if the soil local or regional information on the Department of Agriculture surface is functioning adequately, the specific nature of cover crops. soil will allow water to infiltrate, thus Natural reducing the potential for erosion and Resources Cover and Green Manure Crop increasing the amount of water stored for Conservation Benefits to Soil Quality Service plant use. This function of soil affects water quality, plant growth, and the 1. EROSION - Cover crops

Soil Quality Institute health of animals. In addition, protection increase vegetative and residue cover 411 S. Donahue Dr. of the surface layer resists wind erosion, during periods when erosion energy is Auburn, AL 36832 thus protecting the air resource. Soil high, especially when main crops do not 334-844-4741 X-177 Quality is a critical factor in the furnish adequate cover. Innovative Technical management of natural resources, and planting methods such as aerial seeding, Note No.1 the protection or enhancement of soil interseeding with cyclone seeder, or

April, 1996 quality is the key component of all other equipment may be needed, when resource management assistance main crop harvest, delays conventional activities in the NRCS. planting of cover crops during recommended planting dates. What is Soil Quality? 2. DEPOSITION OF SEDIMENT - Soil quality is the capacity of a Increase of cover reduces upland specific kind of soil to function within erosion, which in turn reduces sediment This is the first note natural or managed ecosystem in a series of Soil from floodwaters and wind. Quality-Agronomy boundaries to: 3. COMPACTION - Increased technical notes on * sustain plant and animal productivity the effects of land biomass, when decomposed, increases management on soil * maintain or enhance water and quality. This organic matter promoting increased information is air quality microbial activity and aggregation of general and covers * support human health and habitation. soil particles. This increases soil porosity broad application. and reduces bulk density. Caution: plant As defined, the terms soil quality, cover crops when soils are not wet, or soil health, and soil condition are use other methods such as aerial seeding. interchangeable. 4. SOIL AGGREGATION AT with conservation tillage systems, cover THE SURFACE - Aggregate stability crops are killed with chemicals and left will increase with the addition of and the on or partially incorporated in the soil. decomposition of organic material by Caution: Research has shown that microorganisms. incorporation of legume cover crops 5. INFILTRATION - Surface cover results in more rapid mineralization. reduces erosion and run-off. Cover crop However, due to delay in availability of root channels and animal activities, such nitrogen from legume cover crop in as earthworms, form macropores that conservation tillage, a starter fertilizer increase aggregate stability and improve should be applied at planting. (Reeves, infiltration. Caution: Macropores can 1994). An ARS study done in Morris, result in an increase in leaching of Minnesota reported dramatically higher highly soluble pesticides if a heavy rain carbon losses through C02 remissions occurs immediately after application. under moldboard plow plots as However, if only sufficient rainfall compared to no-till. It was reported that occurs to move the pesticide into the carbon was lost as C02 in 19 days surface soil after application, the risks following moldboard plowing of wheat for preferential flow are minimal. Cover stubble that was equal to the total crops, especially small grains, utilize amount of carbon synthesized into crop excess nitrogen. residues and roots during the growing season. Long-term studies indicate that 6. SOIL CRUSTING - Cover crops up to 2 percent of the residual organic will provide cover prior to planting the matter in soils are oxidized per year by main crop. If conservation tillage is moldboard plowing” (Schertz and used, benefits will continue after Kemper, 1994). planting of main crop. Increases of organic matter, improved infiltration, 8. PESTICIDE CARRYOVER - and increased aggregate stability reduce Cover crops reduce run-off resulting in soil crusting. reduced nutrient and pesticide losses from surface runoff and erosion. 7. NUTRIENT LOSS OR Increased organic matter improves the IMBALANCE - Decomposition of environment for soil biological activity increased biomass provides a slow that will increase the breakdown of release of nutrients to the root zone. pesticides. Legume cover crops fix atmospheric nitrogen and provide nitrogen for the 9. ORGANIC MATTER - main crop. Legumes utilize a higher Decomposition of increased biomass amount of phosphorus than grass or results in more organic matter. Research small grains. This is useful in animal shows cover crops killed 2-3 weeks prior waste utilization and management. Small to planting main crop, results in grains are useful as catch crops to utilize adequate biomass and reduces the risk of excess nitrogen, which reduces the crop losses from soil moisture depletion potential for nitrogen leaching. Caution: and tie up of nutrients. To prevent nutrient tie ups, cover crops 10. BIOLOGICAL ACTIVITY - should be killed 2-3 weeks prior to Cover and green manure crops increase planting main crop. Tillage tools are the available food supply for used to kill and bury cover crops in microorganisms resulting in increased conventional tillage systems. However, biological activity.

2 11.WEEDS AND PATHOGENS - Summary Increased cover will reduce weeds. Cover and Green Manure Crops as Caution: Research has shown reductions a conservation practice can improve soil in yield are possible in conservation health. Soil quality benefits such as tillage cotton systems following winter increased organic matter, biological cover crops. Reductions are attributed to activity, aggregate stability, infiltration, interference from residue (poor seed/soil and nutrient cycling accrue much faster contact), cool soil temperatures at under no-till than other tillage practices planting, increased soil borne pathogens, that partially incorporate the residue. and increased insects and other pests. One example comes from the Jim Harmful effects from the release of Kinsella farming operation near chemical compounds of one plant to Lexington, Illinois. He reports that another plant (allelopathic) are possible organic matter levels have increased with crops like cotton, but losses can be from 1.9 percent 6.2 percent after 19 reduced by killing the cover crop 2-3 years of continuous no-till (Schertz and weeks prior to planting main crop, and Kemper, 1994). Future technical notes achieving good seed/soil contact with will deal with other conservation proper seed placement. Cover crops have practice effects on soil quality. The goal shown some allelopathic effects on of the Soil Quality Institute is to provide weeds reducing weed populations in this information to field offices to enable conservation tillage (Reeves, 1994). them to assist landusers in making wise 12. EXCESSIVE WETNESS - decisions when managing their natural Cover and green manure crops may resources. remove excess moisture from wet soils, resulting in reduction of “waterlogging” References: in poorly drained soils. Caution: transpiration of water can be a detriment Reeves, D.W. 1994. Cover Crops and in dry climates. Planners should adjust rotations. p. 125-158 In J.L. Hatfield, the kill date of cover crops to manage and B.A. Stewart (eds.) Crops Residue soil water. Management, Adv. Soil Science. Schertz, D.L. and W. D. Kemper. (1994) Crop residue management systems and their role in achieving a sustainable, productive agriculture. ISCO94 Conference. New Delhi.

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