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Impact of Phosphorite on pH, Electrical Conductivity and Water Soluble Phosphorous Extracted from Incubated Citrus Waste Compost

Mussaddiq Khan Khalil, Shuja Ur Rehman Qureshi, Waqar Ali, Mukhtiar Ali and Shabir Khan Utmankhel

Citrus waste having acidic reaction may have additional advantage over other organic residues as compost materials in alkaline calcareous soil but the process of its composting is very slow. In this study an attempt was made to access the release of P from RP added citrus waste during 180 of incubation and its effect on pH and EC of the composting media. Citrus waste consisting pulp, fruits skin and juice with total net weight of 500 g (fresh) were added with 0, 15, 30 and 60 g of RP (equivalent to 0, 3, 6 and 12%, respectively) and were incubated in oven at 36 ± 20°C for 180 days. All pots were also added with 20 ml water and 20 g FYM to optimize the moisture level and augment the microbial decay in pots. Results showed that RP mixed citrus waste had higher pH, EC and more water soluble P as compared to non-treated citrus waste (control) at all incubation intervals of 0, 15, 30, 60, 120 and 180 d suggesting releases of salts and P from RP. These values of pH, EC and water soluble P increased with increase in RP levels and passage of time which could be associated to neutralization of RP with organic acids of citrus and CO2 mineralization with time. It is concluded that addition of RP not only enhanced the quality of compost but could also promote the citrus waste decomposition process. Though the higher RP levels was best in our results, but other levels and their consequent effect on soil and crop yields should be assessed along with their environmental risks for wider and long term recommendations.