Effect of irrigation scheduling on performance of summer legumes grown in 'association of sugarcane

A field experiment was conducted during 2001-03 to find out an optimum irrigation schedule for intercrops grown in association with spring sugarcane, on silty clay-loam soil, having 23.4% moisture at field capacity and 8.6% at permanent wilting point (PWP). Daily evapotranspiration (ET) varied from 3.3 to 16.8 mmlday. Mungbean (Phaseolus radiatus L.), urdbean (F! mungo L.) and cowpea [Vigna unguiculata (L.) Walp.] gave highest yield of 4.1, 3.85 qlha and 73.0 qha, respectively with irrigation at, 1W : CPE ratio of 1.2 compared to 3.25, 2.75 and 6.10 qlha with irrigations at flowering and pod-filling stage. All the intercrops reduced cane yield due to decline in number of millable canes and cane weight. Mean reduction in cane yield was 14.2% with cowpea, 11.5% with urdbean and 9.2% with mungbean. Irrigation at 1.2 IW : CPE ratio resulted in highest cane yield of 97.0 tonnesl ha, being respectively 3.7, 8.1 ; : CPE ratio of 1.0, 0.8, and irrigations at critical growth nd 13.3% higher than IW stages. Sugarcane + cowpea g.we highest mean cane-equivalent yield (1 07.0 tonneslha), being 6.8, 10.0, and 8.7% more than sole sugarcane and intercropping with urdbean and mungbean respectively. Sugarcane inter- cropped with cowpea gave highest gross return of R s 101,6501ha followed by sugarcane alone (Rs 951 90) as against Rs 92,435 with sugarcane + urdbean. Respective Benefit : cost ratio was 0.89, 0.90 and 0.73. Irrigation applied at 1.2 IW : CPE ratio gave significantly highest cane-equivalent yield (1 09.5 tonneslha) with benefit : cost ratio of 0.85 as against 92.4 tonneslha and 0.77 with irrigation at critical growth stages of intercrops.