Soil Phosphorus Dynamics and P Uptake by Medicinal Crops as Influenced by Locally Available Organic Amendments in Light-Textured Soil of Semi-arid Western India

Low phosphorus (P) use efficiency necessitates the high rate of P fertilizer application to achieve the desired crop yield. Locally available organic amendments may be alternative of costly inorganic P fertilizer, but their impact on soil P availability and plant uptake needs further study. Consecutive 2-year field investigation was conducted to examine whether organic amendments had a similar impact on soil P pools and the P uptake by medicinal crops to that of inorganic P fertilizer. The field experiment was conducted with treatments consisting of various organic amendments (farmyard manure, vermicompost, and castor cake) alone or in combination with jivamrut (biodynamic preparation) and recommended dose of inorganic fertilizer. The 2-year cumulative P uptake was significantly higher in the treatment receiving vermicompost (37.5-39.4 kg ha(-1)) and castor cake (35.2-36 kg ha(-1)) along with jivamrut as compared to inorganic P fertilizer (25.4-31.9 kg ha(-1)). The same organic treatments recorded high P recovery as well as negative P balance. There was no significant difference in water-soluble and Olsen P recorded in the treatments receiving inorganic P fertilizer as well as vermicompost + jivamrut and castor cake + jivamrut. However, significantly higher microbial biomass P (MBP) and alkaline phosphatase (ALP) activity was recorded in the treatment receiving organic amendments along with jivamrut. Positive correlation between P uptake, Olsen P, MBP, and ALP activity indicates that organic amendments contributed to plant P uptake by improving soil P availability. Hence, locally available organic amendments were more effective in improving soil P availability than inorganic P fertilizer.