Decomposability and mineralization pattern of coirpith in latosols

Abstract

An investigation on the decomposability and mineralisation pattern of coirpith in latosols was carried out at the Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, Thrissur during the period 1990 – 92. The experimental soil was laterite and the various treatments for mixing with the soil comprised of coirpith raw as well as enriched with Pleurotussajorcaju, urea and rockphosphate. The individual and different combinations of these factors were compared with Glyricidiamaculata applied to the soil. The study involved and incubation experiment and field trial. In order to measure the decomposition of coirpith compared to glyricidia in laterite soil under incubation, the measurement of CO2 evolution was carried our for a period of six months. A field experiment was conducted to study the influence of additives such as microbe, rockphosphate and urea on decomposition of coirpith. The fertility value of the resulting compost was evaluated by estimating pH, organic carbon, cation exchange capacity, available N, P and K of the soil at monthly intervals for a period of one year. Humic and fulvic acid contents of soil were estimated one year after the incorporation of treatments in the soil. The mineralisation of lignin rich coirpith was found to be accelerated due to the addition of both Pleurotussajorcaju and mineral N in the form of urea. With all the treatments and treatment combinations the rate of Co2 evolution was found to be the highest at the second day of incubation and appreciable changes were associated in general, up to 48th day of incubation. There after it declined and attained almost equilibrium values at the end of sixth month. Due to the incorporation of either the glyricidia or coirpith with the without the various adjunctants a steady state of acidic reaction was maintained in the soil. Even with the application of coirpith alone, there was only slight reduction in soil pH. There was not much variation between glyricidia and coirpith treatments on organic carbon content of the soil. Both the microbe and urea enrichment to coirpith reduced the organic carbon content due to faster decomposition whereas it was slightly improved by the addition of rockphosphate. Though there was hike in the CEC of the soil immediately after the addition of organic materials, the values tended to decrease at the end. There was progressive increase in the available nitrogen contents of the soil with the advancement of period of incubation due to the mineralization of glyricidia and coirpith. Among the coirpith treatments, the maximum value was noticed when coirpith was enriched with all the additives. The addition of organic materials also favoured an improvement in available P content of the soil. The contents of available P in the soil increased when coirpith was incorporated with urea. Regarding the release of available K from the soil, the glyricidia incorporation always showed a better performance as compared to coirpith treatments. The microbial inoculation seemed to decrease the humic and fulvic acid contents from their original levels due to decrease in organic carbon content of the soil. This was noticed one year after incorporation of treatments into the latosols.