Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/21/2013
Publication Date: 7/21/2013
Citation: Vories, E.D., Jones, A., Sudduth, K.A., Drummond, S.T., Benson, R. 2013. Effect of drought stress on sensing nitrogen requirements for cotton. ASABE Annual International Meeting. Paper No. 131620324. Interpretive Summary: Current nitrogen (N) management for crop production often results in inefficient use of N fertilizer that can lead to economic losses and environmental contamination. A field experiment was conducted in 2010 - 2012 at the University of Missouri Fisher Delta Research Center to investigate using crop sensors to better synchronize N application and crop N demand for cotton. Plots with total applied N ranging from none to the local recommended rate and timings from all preplant to all 10 days after first flower were observed on irrigated and rainfed cotton. Rainfall varied among the years, which is typical for the Mid-South region. Similarly, observation of significant in-season and end-of-season factors varied considerably among years. The highest correlations with yield were associated with reflectance and plant height; however, as more data are collected the relationship between in-season (sensors) and end-of-season (yield and quality) observations should improve. This research is important for improving N recommendations for cotton. Producers will benefit from fewer excess N applications resulting in wasted fertilizer, energy, and labor, and everyone will benefit from less environmental contamination contributing to problems like the hypoxic zone in the northern Gulf of Mexico.
Technical Abstract: A field experiment was conducted in 2010 - 2012 at the University of Missouri Fisher Delta Research Center to investigate crop sensors and the timing of sensor data collection for both irrigated and rainfed cotton receiving different nitrogen (N) rates and timings of N application. Eleven N treatments were included, with total N ranging from 0 – 134 kg ha-1 and timings from all preplant to all 10 days after first flower. Sensors for canopy reflectance, height, and temperature were driven through the plots once preflower and once postflower each season. While growing degree days indicated that air temperatures were similar all three years, rainfall varied, which is typical for the Mid-South region. Observation of significant in-season and end-of-season factors varied considerably among years. When the data from all three years were combined and subjected to a correlation analysis, most of the correlations were highly significant even if they were not numerically large. For yield, only correlations between both postflower NDVI and height had r greater than 0.5. However, as more data are collected and additional variables investigated the relationship between in-season and end-of-season observations should improve. While these data demonstrate that in-season sensor measurements can detect differences in water and nitrogen status for cotton that result in end-of-season differences in yield and fiber properties, further research, including looking at additional sensors, is needed before recommendations can be made for developing real-time N-application algorithms that account for the effects of drought stress.