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Rock phosphate (RP) is a valuable source of plant available phosphorus (P) however its solubility in alkaline soils is negligible when applied directly. We studied the possibility of solubilizing RP by composting it with municipal solid waste (MSW) and P solubilizing bacteria (PSB). The MSW was composted with 5 and 10% charge rates of RP and/or two PSB strains, viz., Klebsiella pneumonia and Burkholderia cenocepacia for 120 days. These composts treatments were analyzed for total and soluble P contents with fifteen days interval. The compost enriched with 10% of RP and both strains of PSB resulting in the highest total P (2%) and soluble P contents (120 mg kg-1) was selected for raising maize in greenhouse conditions. The treatments included 50 and 100% of the recommended dose of P fertilizer (100 kg P2O5 ha-1), enriched compost equivalent to 50, 100, 150 and 200% of recommended P rate and a mixture of compost and P-fertilizer (75:25) to supply recommended P rate in soil (25% from P fertilizer and 75% of recommended P from enriched compost). Enriched compost at 200% of recommended P resulted in the highest concentrations of N, P and K (18.2, 7.8 and 162 mg kg-1, respectively) in soil. Uptake of N, P and K by maize plants was also the highest (2.9, 0.47, 1.72%, respectively) with this treatment. However, the plant height of maize was maximum (61.4 cm) with recommended dose of P fertilizer but statistically at par with higher rates of enriched compost (58.9 cm). The highest fresh weight (123.6 g) and dry weight (32.3 g) of maize plants per pot were obtained from enriched compost at 200% of recommended P followed by full dose of recommended P fertilizer. Combined use of enriched compost (75: 25) gave maize yield (114.8 g) comparable to sole application of P-fertilizer (121.1 g) and enriched compost (123.6 g). Combined application of enriched compost and P-fertilizer in 75:25 ratio proved equally effective by giving yield comparable to higher application rates of both enriched compost and Pfertilizer. [ABSTRACT FROM AUTHOR]

Present study was carried out at Department of Soil Science and Soil Water Conservation, PMAS-Arid Agriculture University, Rawalpindi, Pakistan to obtain phosphorus (9) enriched compost from municipal solid waste (MSW) including rock phosphate (RP) solubilized with phosphate solubilizing bacteria (PSB) and to evaluate this compost for enhancing maize growth and nutrient uptake. The MSW composting treatments were RP (5 and 10% by weight of MSW) and PSB strains (Burkholderia-cepacia and Klebsiella-pneumoniae) in different combinations, incubated for 120 days. Combined addition of RP (10%) and both PSB strains resulted in the highest contents of total P (2.05%) and soluble P (120 mg/kg). This compost was selected for growing maize as test crop in the greenhouse. Treatments included application of P-enriched compost (PEC) for 50, 100, 150 and 200 percent of recommended P rate for maize and a combination of compost and SSP (75:25), half and full rate of SSP fertilizer. The highest dose of PEC (200%) caused higher concentration (mg/kg) of macronutrients (nitrate-N 18.2; available P 7.8; extractable K 162) in soil. Contents of N P and K in maize plants were 2.9, 0.47, and 1.72 percent, respectively being also higher under this treatment. The PEC (200%) yielded the highest fresh and dry weight (123.6 and 32.3 g/pot followed by that with full rate of SSP. Mixture of PEC and SSP (75:25) also gave results comparable to those obtained from 200% PEC and SSP. Therefore, use of PEC and P-fertilizer mixture is suggested as an economic and efficient way of P input to soil for having sustainable maize yield. [ABSTRACT FROM AUTHOR]