Productivity and P-use efficiency of clusterbean (Cyamopsis tetragonoloba) as influenced by bio-regulators and phosphorus

A field experiment was conducted at Bikaner during 1999 and 2000 on sandy soil to study the effect of bioregulators (thiourea and dimethylsulphoxide) and phosphorus on productivity and P-use efficiency of clusterbean [Cyamopsis tetragonoloba (L.) Taub.]. The study revealed that application of thiourea 5 kg/ha in the soil (split), thiourea 5 kg/ha + dimethylsulphoxide 2 kg/ha in the soil (split), foliar spray of 500 ppm thiourea and foliar spray of 500 ppm thiourea + 100 ppm dimethylsulphoxide proved effective in improving the growth and yield-attributing parameters over the control. The maximum seed yield of 1.988 tonnes/ha was obtained with thiourea 5 kg/ha ++ dimethylsulphoxide 2 kg/ha in the soil (split) along with 17.2 kg P/ha, which was on a par with yield obtained with application of 5 kg thiourea/ha in soil (spilt) and 8.6 kg P/ha, and foliar spray of 500 ppm/ha thiourea and 8.6 kg P/ha. Growth indices, viz. leaf-area index (LAI) and crop-growth rate (CGR) also improved with bio-regulators and phosphorus application. Application of phosphorus up to 17.2 kg P/ha significantly improved the LAI and CGR at 60 and 90 days after sowing (DAS), number of nodules/plant, pods/plant and pod length as well as P-use efficiency. The gum content increased significantly due to phosphorus application up to 8.6 kg P/ha. The maximum P recovery of 47.4 kg/ha was obtained with the application of 8.6 kg P/ha followed by 17.2 kg/ha (26.4 kg/ha). The highest P uptake by seed (10.72 kg/ha) was obtained with 5 kg thiourea/ha + dimethylsulphoxide 2 kg/ha in the soil (split). Soil and foliar applications of thiourea and dimethylsulphoxide recorded higher agronomic as well as physiological efficiency of the applied phosphorus.