An evaluation of Nitrogen and Phosphorus release pattern from organic manure and ERP in organic tea cultivation.

Abstract

Abstract Compost plays a dominant role in most of organic tea lands in Sri Lanka. Hence availability of major plant nutrients in soils amended with Compost is of paramount importance for efficient management of soil fertility in organic tea gardens. An incubation study was carried out at the Tea Research Institute, Hantane, using soils collected from Gami- Seva -Sevana organic tea estate at Galaha with the main objective of evaluating Nitrogen (N) and Phosphorus (P) release pattern in soil, when amended with Compost. Compost was applied at the rate of 25 and 50 mt ha·1 application·1 while keeping the quantity of Eppawala Rock Phosphate (ERP) and Poultry Manure (PM) constant. The treatments were Compost, Compost + ERP and Compost + ERP + PM for both levels of Compost. The treated soils were incubated for 12 weeks and changes in soil available P, NHi + - N, NO3- - N and pH were measured at 3 weekly intervals. Mineralization of organic matter in Compost and Poultry Manure resulted in the release of NHi+ - N and NO3• - N, and subsequent acid production helped in dissolving ERP and release of P in an available form to the soil. Ammonification process reached the maximum at the 6th week, and thereafter NHi + was converted to NO3• by nitrification. Thus nitrification process increased gradually throughout the incubation period. The reduction of soil pH could be mainly due to acidity produced through nitrificatidn. The availability of P reached the maximum at the 3rd week and thereafter it decreased. The treatment, which comprised of Compost at 50 mt ha·1 +ERP+ PM gave the highest availability of P, NH/ - N, and NO3- - N and lowest pH reduction in tea soil.