Effect of levels of phosphorus on seed yield and nutrient uptake of castor (Ricinus communis L.)

Graded doses of phosphate (0 to 210 kg P₂O₅, ha⁻¹) were applied to a low-P red sandy loam Alfisol and castor (Jyothi) was grown as a test crop. Phosphate levels influenced the uptake of phosphorus by castor significantly over control both at flowering and harvesting stages. Apparent recovery of P and Bray's yield showed a gradual decrease with increasing rates of phosphate application. Relatively higher P:S and P:K nutrient uptake ratio i.e. 0.96 and 0.17, respectively, in castor shoots at 210 DAS was observed at 30 kg P₂O₅ ha⁻¹. Castor seed yield and yield attributes were influenced significantly due to phosphate application up to 30 kg P₂O₅, ha⁻¹. Critical P value in soil was found to be 12.8 kg P ha⁻¹ and in castor shoot it was 0.12% at flowering stage.