Effect of method and scheduling of irrigation on water and nitrogen use efficiencies of Okra (Abelmoschus esculentus)

Production of fresh vegetables usually calls for application of large amounts of irrigation water and fertiliser nitrogen (N). Combined application of high rates of water and N leads to excessive leaching of nitrate nitrogen, making most of it unavailable to the plants. Very few studies have been conducted to investigate the combined effect of irrigation method and scheduling on the yield, N use (based on N balance in the root zone) and N uptake (based on N content of plant material) of vegetable crops, especially Okra. A field experiment was conducted in a coarse textured lateritic soil (Haplustalf) of Kharagpur, India, planted to Okra to investigate the effect of method and scheduling of irrigation on yield attributes. Three methods of irrigation: sprinkler, furrow and basin and three irrigation treatments scheduled at 15, 30, 45 and 60% maximum allowable depletion (MAD) of available soil water were studied. The results of the study revealed that on sandy loam lateritic soil planted to Okra crop, furrow irrigation results in the maximum deep percolation (DP) loss while the minimum deep percolation occurs under sprinkler irrigation. Irrigation scheduled at 15% MAD resulted in higher deep percolation loss than irrigation timed at 60% MAD, particularly under surface irrigation methods. The DP loss under furrow and check basin irrigation scheduled at 15% MAD could be reduced to almost half by scheduling at 30% MAD. Maximum fresh fruit yield, nitrogen uptake and nitrogen uptake efficiency of Okra were obtained with sprinkler irrigation scheduled at 30% MAD, whereas the maximum nitrogen use efficiency (NUE) was obtained with furrow irrigation scheduled at 15% MAD. Irrigation schedules with 60% MAD resulted in the minimum fresh fruit yield, nitrogen use, nitrogen uptake as well as the least nitrogen use and uptake efficiencies irrespective of irrigation method. Thus, scheduling irrigation at 30% MAD under sprinkler method of irrigation was found to be the best for Okra crop in sandy loam soil. (C) 2002 Elsevier Science B.V. All rights reserved.