Assessment of Nitrogen Content, Uptake, Partitioning, and Recovery by Cotton Crop Grown under Surface Irrigation and Drip Fertigation by using Isotopic Technique

Abstract Field experiments were carried out through four consecutive years, 1995–1998, to assess the effect of irrigation methods and nitrogen (N) rates on nitrate status of the soil, N uptake, efficiency, partitioning, equivalent nitrogen fertilizer uptake (ENFU) and equivalent total nitrogen uptake (ETNU) by cotton by using the 15N technique. Treatments consisted of two irrigation methods, surface irrigation, and drip fertigation. Drip-fertigated cotton received five different nitrogen rates (0, 60, 120, 180, 240 kg N/ha), while only one rate (180 kg N/ha) was applied to the surface-irrigated cotton. All N fertilizers were applied as urea 46% N. Representative samples of the aboveground portions of cotton plants were harvested from the labeled subplots at physiological maturity and then were separated into leaves, stems, and fruiting forms. Dry matter weight, total N content, N uptake, and 15N excess atom percentage were assessed for each plant fraction, except lint. Soil-water status was monitored by u...