Effect of phosphorus and potassium on growth characters, forage yield, nutrient uptake and quality of lucerne (Medicago sativa)

A field experiment was conducted on well-drained sandy loam soils during the winter, summer and rainy (kharif) seasons of 2003–04 to study the nutritional requirement of major nutrients (P, K) for lucerne (Medicago sativa L.) crop. Application of 300 kg K2O/ha significantly increased the green-forage, dry-matter and crude-pro-tein yields by 17.2, 13.3 and 17.6%, respectively over the control (50 kg K2O/ha), whereas the application of 150 kg K2O/ha significantly increased the green-forage yield only compared with the control in cumulative yield of 12 cuts. Both the lucerne varieties (‘GAUL 1’, ‘AL 3’) were more responsive to higher levels of potassium. Application of 75 kg P2O5/ha along with 300 kg K2O/ha to lucerne variety ‘AL 3’ recorded significantly highest dry-matter yield and maximum uptake of N, P and K, whereas the highest crude-protein yield and the maximum uptake of N and K were obtained with combined application of 75 kg P2O5/ha and 300 kg K2O/ha to variety ‘GAUL 1’. Application of 50 kg P2O5 + 300 kg K2O/ha to ‘GAUL 1’ showed the maximum net return and net incremental cost: benefit ratio, followed by application of 75 kg P2O5/ha + 300 kg K2O/ha to variety ‘AL 3’.