Effect of Nitrogen Fertility On Agronomic Parameters and Arthropod Activity in Drip Irrigated Cotton

A field study was conducted at the Texas AgriLife Research farm near Plainview, Texas, to evaluate the crop growth parameters and arthropod population abundance as influenced by varying nitrogen fertility rates under a drip irrigation production system. Five nitrogen application rates (0, 50, 100, 150, 200 lbs/A) had been deployed annually for seven years consistently to the same experimental units to create maximum discrimination among treatment plots through variation in residual nitrogen. Residual nitrogen levels were monitored on all plots every year. Foliage dwelling mobile arthropods were monitored weekly by using a gas-powered blower sampler that collected insects from the upper half of the foliage, beginning at the initiation of squaring until crop cut-out. Plant parameters including plant height, leaf area, leaf nitrogen, leaf chlorophyll content, fruiting patterns, lint yield, and lint quality were measured. After seven years of continuous application of variable rate of N, residual N levels varied significantly between the 200 lbs/A and lower nitrogen level (<100 lbs/A) treatments. Plots with 150 lbs/A N had consistently the highest root length, plant height, and leaf size. Variation in residual N levels coupled with variable N application resulted in phenotypic expression of nitrogen deficiency in cotton across treatment plots, especially between zero-N plots and N-applied plots. Cotton arthropod pest densities were positively correlated with nitrogen fertility rate.