Improving nitrogen fertilizer use efficiency in surface- and overhead sprinkler-irrigated cotton in the desert southwest

Authors: BRONSON, KEVIN; Hunsaker, Douglas - Doug; MON, JARAI; ANDRADE-SANCHEZ, PEDRO - UNIVERSITY OF ARIZONA; WHITE, JEFFREY; Conley, Matthew; Thorp, Kelly; Bautista, Eduardo; BARNES, EDWARD - COTTON, INC.

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2017
Publication Date: 1/4/2018
Citation: Bronson, K.F., Hunsaker, D.J., Mon, J., Andrade-Sanchez, P., White, J.W., Conley, M.M., Thorp, K.R., Bautista, E., Barnes, E. 2018. Improving nitrogen fertilizer use efficiency in surface- and overhead sprinkler-irrigated cotton in the desert southwest. Soil Science Society of America Journal. 81:1401-1412. doi:10.2136/sssaj2017.07.0225.
DOI: https://doi.org/10.2136/sssaj2017.07.0225

Interpretive Summary: Low nitrogen (N) fertilizer use (NUE) efficiency in cotton is a critical issue with surface-irrigatation, particularly when N fertilizer is dribbled into irrigation water. We compared a soil test nitrate recommendation approach with a canopy reflectance-based N management strategy for two years with surface irrigation, and for two years under overhead sprinkler irrigation in Central Arizona. The surface irrigation studies also compared fertigation of N fertilizer with knifing-N and the addition of the enhanced efficiency fertilizr additive Agrotain Plus to urea ammonium nitrate (UAN). Cotton lint and seed yields increased with N fertilizer in all four site-years. Recovery efficiency (RE) of N at low N fertilizer rates ranged from 21 to 61 % with surface irrigation, and 81 to 97 % with overhead sprinkler. At higher N rates, RE was similar between the two irrigation systems (23-41%). Deep percolation below 1.8 m was 4 to 11 % of applied surface irrigations and rain, but was absent in the overhead sprinkler. Nitrate leaching was apparently the largest N loss pathway in the surface irrigated system. Fertigating UAN into surface irrigation resulted in similar lint yields and RE as knifing-in of UAN. Use of Agrotain Plus with UAN gave similar yields and RE as using UAN alone. Reflectance-based N management saved 50 % of N fertilizer of the full soil-test based dose, without a yield reduction in three of four site-years. Nitrogen fertilizer recommendations were too high with the soil test based approach, and more realistic with the reflectance treatment.

Technical Abstract: Nitrogen fertilizer use efficiency (NUE) is low in surface-irrigated cotton (Gossypium hirsutum L.), especially when adding N to irrigation water. A NO3 soil-test algorithm was compared with canopy reflectance-based N management with surface- overhead sprinkler-irrigation in Central AZ. The surface irrigation studies also compared fertigation of N fertilizer with knifing-in of N and the addition of a urease and nitrification inhibitor (Agrotain Plus [Koch Agronomic Services, Wichita, KS)]) to urea ammonium nitrate (UAN). Cotton lint and seed yields responded to positively to N fertilizer in all four site-years. Recovery efficiency (RE) of N at low N fertilizer rates (60 to 76 kg N ha-1) ranged from 21 to 61 % with surface irrigation and 81 to 97 % with overhead sprinkler irrigation. Deep percolation below 1.8 m was 4 to 11 % of applied surface irrigations and rain, but was undetectable in the overhead sprinkler. Leaching of NO3 was apparently the largest N loss pathway in the surface-irrigated system. Fertigating UAN into surface irrigation resulted in similar lint yields and RE as knifing UAN. Use of Agrotain Plus with UAN gave similar yields and RE as using UAN alone. Reflectance-based N management using normalized difference vegetation index-amber (NDVIA) saved 50 % of N fertilizer of the full soil-test based dose without a yield reduction in three of four site- years. Nitrogen fertilizer was over-prescribed with the soil-test-based treatment. This may have been due to not accounting for N mineralization, which the reflectance method indirectly measures.