Aerobic composting of water lettuce for preparation of phosphorus enriched organic manure

Abstract

In this study, rock phosphate (RP-compost) enriched composts were prepared by mixing rock phosphate with water lettuce (Pistia stratiotes) with and without effective microbes. The treatment comprised of four types and includes control plant material (water lettuce), water lettuce and rock phosphate (WL+RP), water lettuce, rock phosphate, effective microorganisms (WL+RP+EM) and water lettuce, rock phosphate, effective microorganisms and urea (WL+RP+EM+Urea). The present investigation indicates that the nutrients availability was enhanced in the compost with the time span. RP-compost had higher total and available P than normal compost. Inoculation with effective microorganisms increased total P, available P and other nutrient contents in the compost like N, K, Zn and B. The trend of pH shows the production of organic acids in the compost was in the ascending order in the initial days, and it was descending after 45 days. Electrical conductivity (EC) of the compost increase with the time span which shows the availability of the nutrients. The soluble phosphorus was decreased in the initial days of the composting while trend became ascending after 45 days of the composting. The trend of the nitrogen release was similar to the phosphorus, but the released nitrogen remained below the content in the control. The trend of available P in the treatments remained as it was decreasing in the control but the availability of the phosphorus was increased in the other treatments particularly in the treatment where WL, RP, EM and urea was applied. This treatment was recorded as P enriched compost, because carbon to nitrogen ratio was also stabilized in this treatment. Thus, RP enriched compost could be an alternative and viable technology to utilize both low grade RPs and re-use water lettuce plant efficiently.