Using cotton petiole nitrate‐nitrogen concentration for prediction of cotton nitrogen nutritional status on a clayey soil¹

Published with the approval of the director of Arkansas Agricultural Experiment Station. This research was supported in part by funds supplied by Arkansas fertilizer tonnage fees.

Abstract

Soil and petiole nitrate‐nitrogen (NO₃‐N) analyses have been used to monitor the nitrogen (N) nutritional status of cotton (Gossypium hirsutum L.) in Arkansas. The basis for in‐season N fertilizer additions has been NO₃‐N monitoring for the most recently matured leaf petiole. In this manner N fertilizer can be adjusted so that N is not limiting during growing seasons conducive to high yields. The objective of studies reported herein was to determine petiole NO₃‐N levels that define deficient, adequate, and excessive N nutritional status of irrigated cotton growing on a clayey soil. Experiments were conducted on a Sharkey silty clay (very fine, montmorillonitic, nonacid, thermic, Vertic Haplaquept) located on the Northeast Research and Extension Center at Keiser, AR. The experimental design was a 5 by 5 Latin Square with a split plot arrangement of treatments. Subplots were cultivars of cotton, and main plots were N rates of 0, 56, 112, 168, and 224 kg/ha applied as 56 kg/ha splits beginning just before planting, again at pinhead square, and again at 56 or 110 kg/ha at early bloom until all N for a treatment was applied. The N fertilizer was 32% N solution (16% urea‐N and 16% ammonium nitrate‐N). Petioles were collected weekly beginning the week before first bloom and continued for eight weeks. Cotton was harvested and lint yield calculated. Subsequent analysis of petiole NO₃‐N and lint yield were performed using (a) X ² and (b) percent correct predictions on both the actual lint yield versus petiole NO₃‐N content and the lint yield versus the slope of the petiole NO₃‐N content with time. The results indicated that (a) the percent correct predictions were the best predictor, (b) petiole NO₃‐N predicted lint yield losses from the week before first bloom until three weeks later at approximately 80% correct estimates and falls to 50% correct estimates for subsequent weeks, and (c) slope of NO₃‐N with time gives percent correct estimates approximately 50% of the time. These results indicate that petiole NO₃‐N content by itself is useful for determining the N nutritional status of cotton until the third week of bloom.

Notes

Published with the approval of the director of Arkansas Agricultural Experiment Station. This research was supported in part by funds supplied by Arkansas fertilizer tonnage fees.