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Challenging times put a premium on researchBy Doug Rich Cotton acreage in the Missouri Bootheel is going down as the price of corn, soybeans and wheat go up. Cotton acreage in the United States could be down as much as 20 percent this year as more farmers switch acreage to grain crops. Even though producers are responding to market signals by planting more grain crops, those who have made the investment in equipment to plant and harvest cotton will continue to grow cotton on a part of their tillable acres. Cotton has been grown in the Missouri Bootheel for decades and will continue to be grown there for many decades to come. Research to make the most of the acres planted to cotton will continue as well. Cover crop One of those research projects is looking at the management of cover crop wheat in ridge-till cotton. Southeast Missouri and northeast Arkansas are very flat and producers have problems with blowing sand in the spring. Historically it starts getting windy in southeast Missouri in May, usually around Mother's Day. "The tendency over the years has been for the fields to get bigger because we are using bigger equipment," David Dunn, Soil Testing Lab Supervisor at the University of Missouri Delta Center, said. "There are fewer trees as windbreaks." "The common practice is to plant wheat in the middles as a cover crop to reduce the damage from blowing sand," Gene Stevens, crop production specialist at the University of Missouri Delta Center, said. Typically, producers will bed up their cotton in the fall and run a planter behind the "hipper" (lister) to plant wheat in the middles. Most of the farmers do not broadcast the wheat solid on the beds, just in the middles. Some farmers take old grain drills and remove part of the planter units, leaving the ones spaced in the cotton row middles, Stevens said. The most common practice is to mount an air seeder on the toolbar of the hipper and broadcast the wheat seed in the rows. Usually the wheat seed will sprout and peg without being covered with soil and this method saves trips across the field. This wheat is then killed before it reaches maturity to prevent it from pulling moisture and nutrients away from the cotton crop. "The experiment we are conducting now at Clarkton is looking at timing of the burn down," Stevens said. "We are trying to find the optimal time to kill the cover crop." If producers burn down the wheat too early, it does not provide enough wind protection for the emerging cotton crop. The wheat needs at least two joints of growth on it before it is burned down to provide enough stubble to stop the wind. If producers keep the wheat too late it pulls moisture away from the cotton. Another related issue is early application of nitrogen. Producers want all of the nitrogen going to the cotton crop and not the wheat. Test results show that wheat killed in early April was less effective in reducing wind damage to cotton seedlings than wheat killed after the boot stage. Killing wheat after May 9 reduced plant height and leaf area in cotton seedlings. May 9 was the optimal date for killing wheat used as a cover crop in cotton. In order to reduce the cost of buying wheat seed every year Stevens said they are looking at using legumes as a cover crop. "We looked at clover because it matures a little earlier and has the possibility of reseeding itself," Stevens said. Robin crimson clover successfully reseeded itself almost every year before cotton planting. Even with clover, however, allowing the cover crop to mature and take moisture away from the cotton is undesireable in low rainfall conditions. Predict Nitrogen Another ongoing research project at the Delta Center is looking at the use of "on-the-go" sensors to predict nitrogen needs in cotton. Specifically, the research project seeks to determine the sensor model, wavelength and height that gives the best prediction of sidedress nitrogen needs. It is looking at the best growth stage for sensor-based sidedressing. GreenSeeker, Crop Circle and Crop Scan equipment-mounted sensors are being evaluated in the project. There are two types of sensors, passive and active. Passive sensors read reflected light and active sensors shoot a light down on the plant. CropScan is a passive sensor; CropCircle and Green Seeker are active light sensors. Earl Vories, USDA-ARS agricultural engineer at the University of Missouri Delta Center, said the passive type sensors have more frequencies to look at but need to be used in full sunlight, which limits their time in the field. Active sensors take sunlight out of the process and can be used at anytime a producer can get in the field. One test will evaluate cotton leaf color and yield response as affected by nitrogen fertilizer rates and soil types. "But it is just not color," Vories said. "Color is what we all think about because it is obvious to our eyes. It is also looking at near infrared reflectance too. There can be more differences than in just what you see with color." Soil types Tests over the last two years were conducted on silt loam, sandy loam and clay soils. Soil types that can all be found in southeast Missouri cotton fields. "Our soils in this part of the world are quite variable," Dunn said. "In one field it can go from a gumbo to a sand rather quickly. You can't apply one blanket rate of nitrogen over the field." A second test will look at the difference in leaf reflectance between cotton varieties. "We have used three different sensor types and my interpretation to date is that any of them could work," Peter Scharf, associate professor at the University of Missouri, said. "One is not field ready to be an ag instrument but the other two are." To date, they have found that height of the sensor is not really an issue. Sensor readings were taken at heights of 10 inches, 20 inches and 40 inches above the plant canopy. They also found that first square is probably too early to do a good job of determining nitrogen needs of the cotton plant. "The reason being that nitrogen status of the plant is not very well reflected in size of leaf or color at that point," Scharf said. "We tried three different times: first square, mid-square and first flower. We would like to be able to do it at first square because that is when most producers we work with are putting on their in-season nitrogen." Over the six tests they have conducted so far, the nitrogen rates suggested by the sensors are just a little lower than what the typical producer would use. "If you managed nitrogen perfectly, you could make $43 per acre more than with typical nitrogen management," Scharf said. "Over all six experiments, if you followed the system we have set up with the sensors, you would make $10 more per acre at mid-square and $17 more per acre at early flower." It has been proven in work with corn that sensors can measure crop color and predict nitrogen needs of the plant. Extensive testing with 28 on-farm demonstrations were conducted with corn from 2004 to 2006. These are challenging times for the cotton industry. At times like these, producers become more interested in things that will help them survive, like the research being done at the University of Missouri Delta Center and research centers throughout the cotton production regions in this country. Doug Rich can be reached by phone at 785-749-5304 or by e-mail at richhpj@aol.com. 2/25/08 Date: 2/21/08
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