Optimizing nutrient and irrigation requirement of sugarcane (Saccharum species hybrid complex) and French bean (Phaseolus vulgaris) intercropping system

A field experiment was conducted during 201013, on a sandy-loam soil at Pusa, Bihar to find out optimum nu- trient and irrigation requirement of French bean (Phaseolus vulgaris L.) when intercropped with autumn sugarcane (Saccharum spp. hybrid complex). Fifteen treatment combinations consisted of 5 fertility levels [sugarcane + French bean (1: 2) with 100% recommended dose of fertilizer (RDF) to both the crops and residue incorporation, sugarcane + French bean (1: 2) with 100% RDF to sugarcane and 50% RDF to French bean and residue incorpo- ration, sugarcane + French bean (1: 2) with 100% RDF to sugarcane and 100% N to French bean and residue re- moval (existing recommendation), sugarcane + French bean (1: 2) with 100% RDF to sugarcane and 100% N and P to French bean and residue incorporation, sugarcane + French bean (1: 2) with 100% RDF to sugarcane and 100% N and K to French bean and residue incorporation) and 3 irrigation schedules [no irrigation, 1 irrigation at 45 days after sowing (DAS) and 2 irrigations at 45 and 75 DAS] were evaluated in factorial randomized block design with 2 additional treatments as sole sugarcane and sole French bean. Application of 100% RDF to sugarcane and French bean with residue incorporation produced significantly higher grain (1.15 t/ha) and haulm yield (1.90 t/ha) of French bean. The treatments of sugarcane + French bean with 100% RDF to both the crops and residue incor- poration, sugarcane + French bean with 100% RDF to sugarcane and 100% N and K to French bean and residue incorporation and sugarcane + French bean with 100% RDF to sugarcane and 100% N and P to French bean and residue incorporation being similar noticed significantly enhanced cane-equivalent yield (100.0, 95.8 and 94.8 t/ ha), gross returns ( 2,29,400; 2,19,600 and 2,17,300/ ha), net returns ( 1,41,900; 1,33,100 and 1,30,100/ha) and benefit: cost ratio (2.62, 2.53 and 2.49), respectively, over rest of the treatments. The same treatment also ac- counted for higher land-equivalent ratio, area-time equivalent ratio and N, P and K uptake of sugarcane and French bean with greater available N, P and K status in post-harvest soil. Among the irrigation schedules, the highest cane yield (89.0 t/ha), French bean grain (1.20 t/ha), haulm yield (1.98 t/ha) and cane equivalent yield (106.0 t/ha) were recorded in treatment that received 2 irrigations at 45 and 75 DAS. Similarly, the maximum land- equivalent ratio, area time-equivalent ratio, gross returns, net returns, benefit: cost ratio and N, P and K uptake was noted from the enhanced levels of irrigation. The sugar yield was significantly increased with each successive increase in level of irrigation. Considering the total productivity and economics, sugarcane + French bean (1: 2) with 100% RDF to sugarcane and 100% N and K to French bean and residue incorporation, could be adopted un- der similar agroecological situations with twice irrigation up to the period of French bean at 45 and 75 DAS and normal irrigation for sugarcane after harvest of French bean.