Water Resources: BIOEN3 Issues & Opportunities in March 2012 Bioenergy Generation Factsheet 3.2.5 CRP Conversion: Missouri As CRP contracts expire, producers must decide whether to renew the contract or convert to cropland. There are several keys areas to consider before taking action. monitored to ensure a successful grain crop production. Nitrogen (N) increases during CRP because of organic matter in the soil. During the summer, the nitrogen will be released at a high rate but is often released too late to be used by a first-year corn crop. If soybeans are planted the first year out of CRP, nitrogen released during that summer and fall will be available to the second-year corn crop. Soil Quality CRP fields typically have increased soil organic matter, soil tilth and soil pore space. These changes improve water availability for plant use, and reduce water runoff and soil erosion. Crop roots grow better because there are more earthworm burrows in the soil. Soil compaction has been reduced because CRP fields have not been tilled for many years. Broadcast urea ammonium nitrate (UAN) will become tied up if it cannot fall through the residue to the soil. Up to half of broadcast urea-nitrogen can be lost to the atmosphere, so it is best to inject or work it into the soil with tillage. Taking a soil test before planting and then applying fertilizer or lime as needed is the best way to manage soil nutrients. The effects of tillage on soil: Established soil pores are broken, resulting in less water infiltration and more runoff Organic carbon and nitrogen decline rapidly after tillage The advantages of no-till crop production: Maintains soil structure and organic matter Slows mineralization of carbon and nitrogen that occurs when sod is killed Crop Selection Selection should be based on: Personal preference Price outlook Fertility levels Potential pest problems (weeds, diseases, insects, etc.) Amount of vegetative cover Soil Fertility Soil ph and potassium (K) levels remain relatively constant during CRP. Phosphorus levels should be
Soybeans Soybeans have a more flexible planting date than corn. There is a wide range of post-emergence herbicides available, such as Roundup and Liberty. Using Roundup with Roundup Ready soybeans controls the sod and broadleaf weeds in the crop. Planting soybeans right away allows more time for organic matter to decompose and to increase organic nitrogen available for future crops. Soybeans can also be planted if the presence of soil insects is unknown. Other things to consider: Atrazine can be used to control the sod and annual weed species. If there is an infestation of perennial broadleaf weeds, planting corn would be best because Banvel, Clarity, Stinger, Roundup or 2,4D can be used. Other things to consider: Planting date Nitrogen requirements Soil insects Corn needs an early planting date to avoid yield loss, and there may be limited time for spring sod control because of it. Early planting dates may also mean planting into cool, wet soils, which may result in stand loss. Soil ph Presence of soybean pathogens Inoculation for nitrogen fixation In a no-till field, corn will require more nitrogen because of limited nitrogen release in the soil the first year out of CRP. Most of the soil fungi that cause early-season diseases and root rots in soybeans can live for a long time in the soil. In general, planting quality seed under the best possible conditions and avoiding seed or seedling stress will reduce the loss to earlyseason diseases. Soybean cyst nematode (SCN) eggs can survive in the soil for at least 9 years. It is best to assume that if SCN was present in the field before the land went into CRP, it is still there. Corn Corn is a good crop to plant because seed placement and depth are not as critical as they are with other crops. Corn is also better suited to low ph soils. White grubs and wireworms can be expected in the CRP fields. Solar bait traps can be set 3 weeks before planting and then checked just before. If the traps average one wireworm per trap, granular soil insecticide is recommended. Other insects that may be present: Glassy cutworm Bronzed cutworm Common stalk borers (not a problem if the CRP field was pure grass) Sod webworms Seed corn maggots Diseases are not likely to be more prevalent or severe in CRP converted fields than previously tilled fields.
Grain Sorghum Grain sorghum can be planted later than corn, which means warmer, dryer soils. Atrazine can also be used to control sod and weeds in the crop. The seed is smaller and difficult to plant at the proper depth in heavy residue. There are also limited post-emergence grass herbicides available for grain sorghum. Wheat Insects, such as wireworms, and weed control can be big problems for winter wheat. There are no selective herbicides to control perennial grasses. It is difficult to plant the seed at the proper depth in heavy residue, especially in no-till fields. Wheat is more sensitive to improper seed placement than other crops. Certain pathogens present in other grass species may spread to wheat. For example, take-all is a disease caused by a soil-borne fungus that can infect barley, bromegrass, wheatgrass and quackgrass, and then move to wheat. What to do if take-all was a problem in the CRP planting: Destroy CRP planting as far ahead of the wheat crop as possible to reduce inoculum in the field Till to break up crowns and roots to speed up decomposition of infested plant matter Fertilize properly to reduce losses Other diseases that may be present in wheat after CRP: Helminthosporium diseases Fusarium diseases Foliage diseases Virus diseases If wheat is to be planted, it is best to choose wheat varieties with resistance to diseases likely to occur in the field. In a rotation, it is best to plant wheat 2 or 3 years after the first cropping.. Mowing and Herbicide Application The most effective method to control sod and weeds is a combination of mowing and applying herbicide during the summer and fall before the cropping season. It allows for a more uniform herbicide application. Cool-season species control: Mow with flail chopper from mid-july through August Allow 8 12 inches of regrowth Apply herbicide in mid- to late September Herbicide should be applied to cool-season grasses at least 2 weeks before a killing frost. Warm-season species control: Mow fields in June Allow 8 12 inches of regrowth Apply herbicide in mid-july to mid-august Recommended rates: Cool-season Roundup Ultra at 1 to 1.5 qt/acre or Touchdown at 0.8 to 1.2 qt/acre. Use the higher rate for orchard grass and bromegrass. Warm-season
Roundup Ultra at 2 qt/acre or Touchdown at 1.6 qt/acre. Spring Vegetation Management Mowing in the spring will help control perennial cool-season grasses and help establish corn and soybean stands by removing prairie vole habitats. Roundup or Touchdown can control coolseason grasses effectively in the spring. Before planting soybeans, it is best to apply 2,4-D ester at least 7 days in advance. Plan to apply herbicide during the first week of May and plant in mid-may. Controlling sod with spring herbicide applications may be harder in soybeans than in corn or grain sorghum. Using Roundup or Touchdown to control cool-season grasses may require several weeks to achieve results. For rapid control of vegetation, apply Gramoxone and follow with another treatment 10 to 21 days later. Weather restrictions for burning: Wind speed less than 15 mph Relative humidity 30 60 percent Air temperature 45 75 degrees Fahrenheit Cloud cover less than 70 percent Prairie Voles Prairie voles, also known as field mice, may be a major pest for corn production in fields converted from CRP. Perennial grasses and broadleaf weeds provided a habitat for large populations. The animals will dig into the planter slot to eat the seed or small seedling. Once the seedling is 8 10 inches tall, the prairies voles will not eat it. All fields should be scouted at least 30 days before planting. If there are 5 or more colonies per acre, control measures should be taken, especially if corn is going to be planted. Control Techniques: Managing Vegetation with Fire Fire may be an option to remove old top growth and stimulate new growth in fields that have not been mowed since they were in CRP. To prepare for a burn, mow or disk around the area. The width of this area should be two times the height of the established vegetation. Winter wheat and bluegrass can also be drilled into the area to reduce soil erosion and to act as a fire retardant. Close mowing reduces cover Hay removal removes cover, do this 2 3 weeks before planting Controlled burning removes cover and food, usually done in late winter or early spring Early pre-plant herbicide applications reduces cover, do this at least 30 days before planting Tillage destroys cover, food and vole colonies It is best to burn in late February through early April when the soil is still moist.
Alternative feeding can be used where scouting was not done. This provides enough food for the voles for at least 3 to 4 weeks and should be done a few days before planting: Broadcast whole kernel corn at 2 bushels/acre Broadcast cracked corn at 4 bushels/acre (large populations) or 2 bushels/acre (small populations) * Prepared by Erica Jobman and Tom Franti