EFFECTS OF INCREASING NITROGEN FERTILIZER RATES IN CONSERVATION TILLAGE COTTON

摘要

Conservation tillage is now the primary method of growing cotton in the Tennessee Valley of Northern Alabama. One test was conducted in 2004 to evaluate nitrogen (N) fertilizer rates under various conservation tillage systems. Another test was conducted in 2003 and 2004 to evaluate N fertilizer rates needed by irrigated cotton when planted into a small grain cover crop. Results in 2004 indicate the current N recommendation of 60 pounds per acre for conservation tillage cotton without cover crops and90 pounds of N per acre when a small grain cover crop is used appears adequate for optimum yields. Cotton no-tilled into rotations of soybeans or double cropping of wheat with soybeans required 90 pounds of N fertilizer for optimum yields in this study.This is higher than the current recommendation of 60 pounds of N per acre. Cotton planted into corn residue also indicated a very positive trend toward higher yields with the 90 pound rate of N fertilizer. Irrigated cotton yield response to N fertilizerrates was similar each year. Cotton yields were optimized when an N fertilizer rate of 130 pounds per acre was applied following planting into a small grain cover crop.