Crop Insurance Today May 2013 - (Page 42)

Cover Crops CropInsuranceTODAY • provide soil erosion control • absorb and retain/recycle nutrients • protect water quality • maintain and/or improve soil organic matter content By Dr. Mark Zarnstorff, NCIS Crop production has taken many different twists and turns over the past decade or two. We have seen a rise in the use of transgenic crops that help control insects and weeds. We have seen an increase in the use of conservation tillage with some producers adopting a no-till approach to crop production. We have also seen the adoption of high technology use with yield monitors, variable rate seeding and fertilizer and pesticide application. The most recent change is the use of cover crops in crop production. The questions many people have are what are “cover crops” and why are farmers starting to use them. Cover Crops– A Simple Definition What is a cover crop? The simplest definition of a “cover crop” is a crop that is grown on the field during a time of year when the primary crop is not being grown. The primary crops grown in a large area of the U.S. are corn and soybeans, which are seeded in early spring, grow throughout the summer and are harvested in mid- to late autumn. This leaves the late autumn, winter, and early spring with no growing crop in the soil. This time period can be when a fair amount of the yearly precipitation total occurs and because of this there is a great potential for soil erosion, both by water and wind, if there is not enough stubble or other types of residue covering the soil surface. The use of cover crops is not really new; in fact cover crops have been used throughout the world for quite some time. There are many advantages that can be gained by the use of cover crops: 42 MAY2013 • maintain and improve soil structure • fix atmospheric nitrogen • provide weed control • provide forage Let’s look closer at the various benefits. The first I have already mentioned - prevent soil erosion. This is very important in areas where there is a fair amount of relieve or roll to the land. The other factor is that a good amount of moisture occurs during the period when the primary crop is not being grown. Crop residue provides a good way to reduce soil erosion; however, there are many times that there is very little crop residue left after harvest such as when corn is harvested as silage, after soybean harvest, when corn stalks or wheat straw are harvested for biomass/ethanol and straw board production or used as animal feed or bedding. The removal of the residue leaves the soil surface vulnerable to water and wind erosion. The use of a cover crop may provide cover for the soil surface as well as root growth that will keep the soil from moving during the times before planting of the major crop the next season. The next two benefits are similar to soil erosion prevention. The nutrients that are applied for crop production are not all removed when the crop is harvested. This is especially true of phosphorus and nitrogen in the form of nitrates. Cover crops capture or “scavenge” excess nitrogen and keep nitrogen from reaching the ground water or running off with surface water. This is the case in areas such as the East Coast where much of the crop production areas are near rivers that eventually flow into the various bays of the oceans. Nitrogen and phosphorus can be leached or lost from soil erosion resulting in a major potential for water quality problems. When the nutrients are scavenged they are available for the subsequent crop. Soil organic matter is an important factor in crop production. The increased use of burning fossil fuels has increased the CO2 of the atmosphere and one of the ways greenhouse gasses can be decreased is by “capturing” it in plants. The plant takes in CO2 as part of the photosynthesis cycle and uses that as the building blocks of the sugars that becomes the plant. The more plant material that can be produced results in more soil organic matter. This is also part of the recycling of the nutrients that we touched on above. The soil organic matter, along with the humic acids that are part of the breakdown of the plant matter, are the “glues” that improve the soil structure. The improvement of soil structure allows for greater infiltration of water into the soil, so that more water can be stored in the soil and less will be lost due to water going over the surface of the soil. The fixing of atmospheric nitrogen is a major source of nitrogen for many of the crops grown in the U.S. The crops that can do this are often termed legumes and they accomplish this “fixing” of the nitrogen through a relationship with bacteria called rhizobia. The rhizobia/plant interaction is very specific and the type of rhizobia that will work with soybeans is different than the type that will grow and produce nitrogen with alfalfa. The use of legumes is not new in crop production. Legumes have been grown in rotation with other crops for many years. The annual legumes, such as soybeans and crimson clover, produce enough nitrogen for their needs and often additional nitrogen is released to the crops following them. Generally, a perennial legume will produce more nitrogen that is then available for the crops following in rotation, but this usually takes a couple of years. Weed control is a potential benefit from the use of cover crops. This benefit requires that there is enough growth of the cover crop for it to be a “mulch” and usually shade out the young, developing weed seedlings. The production of biomass by the cover crop can be both a good thing and bad thing. This

Table of Contents for the Digital Edition of Crop Insurance Today May 2013

President's Message
2012 Year in Review
2013 Annual Convention Great Success!
Max Erickson Awarded Outstanding Service Award
Larry Heitman Pesented Leadership Award
Leadership of NCIS Regional/State Crop Insurance Committees
How Do Farmers Manage Risk When It Comes in So Many Forms?
Step 9-Monitoring and Controlling the Farm Business Q: How do I monitor progress over time?
Three Industry Stalwarts Presented Lifetime Achievement Awards
Cover Crops
Crop Insurance Plan Comparison
NCIS Retirements

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