EFFECT OF IRRIGATION REGIMES, PLANT POPULATION AND PHOSPHORUS LEVELS ON THE YIELD ATTRIBUTES AND YIELD OF SOYBEAN (Glycine max (L.) Merrill)
Field experiments were conducted at Tamil Nadu Agricultural University, Coimbatore, India during the summer (January – April) and kharif (June – September) seasons of 1994 and 1995 in a split plot design. The main plot consisted of three levels of irrigation, with irrigation water/cumulative pan evaporation (IW/CPE) ratios of 0.40, 0.60 and 0.80, and three levels of plant population (0.33, 0.44 and 0.66 million plants ha –1). The subplot treatments consisted of three levels of phosphorus (80, 100 and 120 kg P2O5 ha –1). The results revealed that irrigation at IW/CPE 0.80 with a plant population of 0.66 million plants ha –1 and a P level of 100 kg P2O5 ha –1 is promising in obtaining maximum yield in soybean. Under an irrigation regime of IW/CPE 0.80, the total water consumption varied from 450 to 533 mm, while it varied from 350 to 438 mm at IW/CPE 0.60 and from 250 to 393 mm at IW/CPE 0.40.