Nitrogen Fertilizer Recovery Efficiency and Nitrate Leaching in Cotton for Different Irrigation Systems.

Nitrogen fertilizer recovery efficiency (NFRE) in irrigated cotton is often reported as being low, e.g., < 50 %. We present data from West Texas of NFRE of cotton for different irrigation systems. Nitrogen content and biomass of cotton was determined at first open boll. Nitrogen fertilizer recovery efficiency averaged 15, 40, and 75 % for furrow irrigation, LEPA (low energy precision -center pivot), and subsurface drip (SDI), respectively. The differences in NFRE were attributed not only to the frequency and quantity differences in the various irrigation modes, but also to the fertilizer timing and number of splits. Specifically, N fertilizer was added in one or two splits at the planting and squaring in furrow irrigation. In LEPA, N is fertigated/injected through the irrigation system several times during the season in 30 lb N/ac doses. In SDI 1-3 lb N/ac day were injected on about 30 days over a 5- 8 week period. Residual profile nitrate (NO₃) (0-1.5 m) was greatest in furrow irrigated fields. Leached NO₃, i.e., extractable soil NO₃ below 1 m, was also greatest in furrow irrigated fields.