Evaluation of Cotton Response to Rates, Sources, and Timing of Nitrogen Application by Petiole Analysis1

Abstract

AbstractThree experiments were conducted on a calcareous clay loam soil to determine the relationship between nitratenitrogen content of cotton (Gossypium barbadense) petiole and yield; and to employ the petiole analysis technique for evaluation of calcium nitrate, ammonium nitrate, and urea as N sources and evaluation of timing of N application. Increase in cotton yield associated with unit increment of petiole nitrate was proportional to the decrement from the maximum and the data were fitted to the exponential equation of Spillman. Cotton yield was not affected by N source and time of application, but petiole nitrate was sensitive to both. Calcium nitrate was the best fertilizer and the availability coefficients of N in ammonium nitrate and urea as a fraction of that in calcium nitrate were 0.714 and 0.511, respectively. Splitting the applied N in thirds proved superior to a split into two applications or to a single total application, and the availability coefficients ratios were 20.889, and 0.566, respectively.