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Nitrogen Uptake and Residual Soil N in San Joaquin Valley Cotton

R.B. Hutmacher, M. Keeley, R.L. Travis, W. Rains, R. Delgado, S. Perkins, B. Weir, R. Vargas, S. Wright, D. Munk, B. Roberts and M. Jimenez Jr.


The first two years of study have been completed in a multi-location study to evaluate the response of a current California Acala cotton variety to applied N under a range of soil types, production conditions, and levels of residual soil N. Total calculated applied N plus changes in soil NO3-N during the period from spring to fall (planting versus post-harvest) ranged from a low of 136 to a high of 252 lbs N/acre across the different N treatments and study locations. At the Westside Research and Extension Center location, the only site (in 1996) with a significant yield reduction with low N applications, average applied N plus depletion of soil NO3-N to a depth of 8 feet averaged 164, 206, 214, and 226 lbs N/acre in the 50, 100, 150 and 200 lbs N/acre treatments in 1996. In 1996, with only one site with a significant yield reduction with decreasing amount of applied N, petiole NO3-N levels during the flowering and boll maturing stages were within levels established as sufficient according to University of CA recommendations for petiole NO3-N. during the entire growing season at six out of eight locations. In 1997, there was a broader range of petiole NO3-N levels, with three out of the eight locations showing borderline sufficient or deficient levels during flowering and boll maturation. In 1997, three locations (out of eight total) showed significant yield reductions at N applications levels of 100 lbs N/acre or less.

Reprinted from Proceedings of the 1998 Beltwide Cotton Conferences pp. 654 - 658
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998