Effect of coir pith on physico-chemical and moisture retention properties of selected soil groups of Kerala

Abstract

An investigation on the effect of coir pith on physico- chemical and moisture retention properties of selected soil groups of Kerala was carried out at the Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, Thrissur during the period 1991-93. Three major soil groups selected for the experiment were coastal sandy, laterite and red. Pots were filled with these soils at the rate of 10 kg soil per pot. Coir pith at the rate of 5 t ha -1, 10 t ha-1, and 20 t ha-1, was added in the soil. An absolute control treatment with no coir pith application and a control treatment with farm yard manure applied at the rate of 5 t ha-1 were maintained. One set of pots was used for incubation study for a period of one year. The soils were maintained at field capacity. Samples were collected from the pots at quarterly intervals and analysis was done for various physico- chemical properties like volume – mass relationships, moisture retention at tensions of 30, 500, 1000 and 1500 kPa and organic carbon. At the end of one year after incubation water stable aggregates and cation exchange capacity were analysed. Another set of pots was used for in vitro study. Cocoa (Theobroma cacao L.) seedlings were raised in the pots. Irrigation was given as and when the plant showed temporary wilting symptoms and the interval between the consecutive irrigations was noticed for different treatments. At the end of the sixth month the plants were taken out and analysed for nitrogen, phosphorus and potassium and uptake of these nutrients were calculated. Soil samples were also collected from the pots to study the available nitrogen, phosphorus and potassium contents. It was noticed that the application of coir pith significantly improved the bulk density, maximum water holding capacity and per cent pore space. There was a significant increase in the moisture retention at different tensions. Water stable aggregates were measured and per cent aggregate stability, mean weight diameter, structural coefficient and stability index showed significant increase with the increasing levels of coir pith. Soil moisture retention at different tensions was significantly influenced by the addition of coir pith. As the level of coir pith increased soil moisture retention increased. Organic carbon content showed an initial increase to a period of six months and subsequently decreased. Cation exchange capacity showed an increasing tendency with increasing levels of coir pith. Significant correlation was obtained between various physical properties and organic carbon content of the soils. After the removal of the crop the available nitrogen content of the soil decreased with increasing levels of coir pith whereas available phosphorus and potassium contents increased with increasing levels of coir pith.