Grain yield and phosphorus uptake by wheat as influenced by long-term phosphorus fertilization

Phosphate reactions in the soil have important implications for crop growth and its nutrition to plants. Using a 40 years old long-term fertility experiment, we studied the fate of different sources of applied P into its nutrition to wheat in calcareous soils in a pearl millet-wheat cropping system during rabi 2009 and 2010. Results showed that water soluble sources of phosphatic fertilizers (Single super phosphate, Diammonium phosphate, Urea ammonium phosphate) were found superior over partially water soluble (nitrophosphate) and mineral acid soluble (RP) sources in terms of grain yield and P uptake. With increasing levels of P from 60 to 120 kg P2O5 ha-1, grain yield and P uptake increased significantly. Cumulative mode of P application was found the best for grain yield and P uptake as compared to direct and residual mode. The available P, saloid-P and Al-P were positively and significantly correlated with grain yield (r = 0.829** to 0.894**), straw yield (r = 0.833** to 0.890**), P concentration in grain (r = 0.666* to 0.749*), and total P uptake (r = 0.860** to 0.928**). Multiple regression equations between yield and P uptake and various inorganic P fraction of soil also indicated that saloid-P and Al-P were the important forms of inorganic P and contributed mainly towards grain and straw yield and total P uptake. Key words: Phosphatic fertilizers, wheat grain yield, phosphorus uptake.