Phosphorus Utilization from Rock Phosphate by Maize (Zea mays L.) Through Integrated Organic Manures

Abstract

Pakistan is a subtropical, semiarid country of 79.61 M ha area, which relies heavily on agricultural production to supply food for its rapidly increasing population of over 135 million. The country is divided into four regions, two of which contain the majority of the flat topographic plains having the bulk of 21 M ha of cultivated land. There are two general cropping seasons in tropical flat plains of Pakistan i.e. Rabi (winter) and Kharif (summer) season. Cotton, maize, rice and wheat are the main crops of Pakistan. Majority of Pakistani soils are calcareous and alkaline with pH in the range 7.5 to 9.5. These soils reduce the availability of P considerably as P is converted to insoluble forms at this pH. Overall, P fertilizer application to Pakistani soils is inadequate. Energy crisis, high prices of phosphatic fertilizers and their shortage at peak crop requirement has become a serious issue in Pakistan. Rock phosphate (RP) has low bio-solubility of about 0.1 % under alkaline conditions if applied directly. Therefore, bio-solubilization RP to release P needs to be boosted up using some innovative approaches. Pakistan by default contains considerable quantity of economical reasonable quality RP in Abbottabad and Haripur districts. However, extensive scientific work is needed so that local rock phosphate may be used for P nutrition. Under this research plan four consecutive experimental units were performed to enhance total and water soluble P content in RP. In the first study, local and imported rock phosphates in combination with different materials of organic nature were applied. The purpose of above research proposal was to explore role of organic materials for P release from local & imported RP and P uptake by maize crop. Maximum solubilization of P was achieved when filter cake press mud (FCP) was applied in combination with rock phosphate. The 2nd study comprised of 7 treatments with three replications. Use of dewaxed filter cake press mud was evaluated as most suitable source of local rock phosphate. Third study of this research proposal comprised of 7 treatments which were replicated thrice. Combined use of FCP with RPR and TSP performed better than their individual use. Use of organic amendment improved soil organic carbon fraction of soil compared to control. The 4th study was conducted in the field using RCBD with five treatments. Exogenous application of FCP along with indigenous Hazara rock phosphate RPR and NK proved as better nutritional source compared to control. Further, application of selected organic manure (dewaxed filter cake press mud) improved soil organic carbon fraction in similar environment condition.