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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #199224


item Vories, Earl

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/31/2006
Publication Date: 8/31/2006
Citation: Vories, E.D. 2006. Using sensors to predict nitrogen needs in cotton [Meeting Abstract]. Delta Center 45th Annual Field Day, Portageville, MO., August 31, 2006. University of Missouri P.4.

Interpretive Summary:

Technical Abstract: Applying nitrogen (N) in excess of crop needs results in unused soil nitrate and increased potential for N loss. Unused nitrate can move to groundwater, to surface waters, or denitrify from the soil into atmospheric greenhouse gases. Farmers want to be good environmental stewards; however, many ideas proposed for reducing N loss from fields create the risk of reduced productivity and profitability. To reduce N loss while maintaining productivity, several research groups have recently explored variable rate N fertilizer application. Advances in reflectance sensor technology have allowed development of sensing/applicator systems for assessing N needs and automatically adjusting N application rates based on the principle that plants under N stress are lighter in color and reflect more light than plants with sufficient N. Researchers in Missouri and other states have been working cooperatively to develop recommendations for N fertilizer application on corn based on reflectance measurements. Research is underway at the Delta Center to apply the same approach to cotton. Research plots with N application rates ranging from 0 to 200 lb N/acre were established on a Tiptonville silt loam at the University of Missouri (MU) Lee Farm near Portageville and a Bosket fine sandy loam at the MU Rhodes Farm near Clarkton. Reflectance readings were made at approximately two-week intervals beginning shortly after the first square growth stage and are expected to continue through physiological maturity. Supporting measurements include soil N content, leaf chlorophyll content, and plant growth and maturity indicators. Similar measurements were also made in an ongoing N study on a Portageville clay at the MU Lee Farm. The goal of this research is to develop recommendations for reflectance-based N application. In this way, optimal rates can be applied to every part of the field, rather than making field-wide blanket applications and knowing that some areas of the field will receive too much N while others don’t receive enough. In this way, both the economic impact on the grower of applying more N fertilizer than needed and the environmental side-effects of excessive N application will be reduced. In addition, indirect effects on growth and maturity resulting from excessive or deficient N can be better managed.