SURENDRA BABU, PANAND SINGH, MAISHNAM2016-09-142016-09-142014http://krishikosh.egranth.ac.in/handle/1/76561The present investigation entitled “Comparison of Reduced P Application and Supplemental Enhancement of Selected Nutrients on their Availability and Yield of Rice Crop (Oryza sativa L.) in High-P Soil” was carried out at AICRP on Micronutrients, Hyderabad Centre, ANGRAU to determine (i) the availability of Nitrogen, Sulphur, Zinc and Boron under different P regimes of the same soil. (ii) to determine whether reducing the P application or supplementing additional nutrients is a better choice in high- P soil in terms of yield of paddy crop and (iii) to identify the most required nutrient among N, S, Zn, B, Fe Spray to augment the yield by supplementing them beyond the current recommended levels. One laboratory experiment was conducted after developing low (16) , medium (40), high (63 ), v. high (102 ) and v.v high (128 kg P2O5 ha-1) soil- P fertility regimes of a low P soil using its P- fixation characteristic curve and by employing 3 levels each of N, Zn, S and B. Net house experiment was conducted employing a high- P soil (89 kg P2O5 ha-1) using paddy as test crop with nine (9) treatments comprising different individual supplementation doses and their combination of N, S, Zn, B, Fe Spray and Multimicronutrient Sprays in combination of two levels of P application (100 % and 70 % RDP). The development of different P – fertility regimes using P- fixation characteristic curve was satisfactory. Under laboratory condition, the availability of N, S, Zn and B increased with increasing levels of their applications, irrespective of soil P fertility regimes in 45 days of contact period. Likewise, the availability of N and S increased with the increase in contact period from 15 to 45 days. However, in case of boron and zinc, their availability decreased as the contact period in the soil increased from 15 to 30 days and there after increased by 45th day of incubation. The enhanced P- fertility regime had significant effect on availability of nutrients under study under laboratory condition. The nitrogen availability increased from 223 to 299 kg N ha-1 in the same soil as the P- fertility regime shifted from low to v.v high thereby registering a 34 per cent enhancement. Sulphur extraction by CaCl2 extractant increased by 46 per cent in 45 days from 15.39 to 22.53 mg S kg soil-1 with increased P – fertility regime. However, the hot water soluble boron extraction decreased by 22 per cent (from 3.28 to 2.55 mg kg-1) as the P fertility regime of the soil increased from low (16 kg P2O5 ha-1 to v.v high (128 kg P2O5 ha-1) status. The Net House experiment result revealed that additional application of nutrients like N, S, B, Zn and their combination beyond their recommended levels affect the yield of paddy in a high P soil. Application of boron @ of 25 % RD B helps in increasing the paddy grain yield most by 16 per cent, S by 13 per cent, N by 7 per cent and N + S by 22.4 per cent indicating that boron is most useful to increase the yield in a high- P soil even when its content is above critical limit. This observation is also back- up with incubation study results varying applied boron availability decrease with the increase in the soil- P fertility regime. The choice between reducing the P- fertilizer in a high- P soil without affecting the yield and enhanced yield with addition of supplemental doses of nutrients like boron or sulphur will determine whether the reduction in input cost is priority or improving the productivity with little more expenditure. Both these aspects need field level verification and also will determine how long the accumulated P in the soil with support such activities.enNUTRIENTS, YIELD, RICE, CROP, HIGH- P, SOILThesis