Influence of multi purpose trees on physico-chemical properties of soil in coconut based agroforestry systems

Abstract

A characteristic feature of tree based land use system is their potential to improve the physico chemical attributes of soil and overall site productivity. The effects of intercropping of three fast growing multipurpose trees viz. Casuarina (Casuarina equisetifolia L.), Ailanthus (Ailanthus triphysa (Dennst.) Alston) and Leucaena (Leucaena leucocephala (Lam) de Wit.) planted in one year old coconut plantations, on soil physico-chemical and biological properties were studied in a field experiment laid out at the Instructional farm,  Kerala Agricultural University, Vellanikkara. The experiment was laid out during 1993 in one year old coconut plantation spaced at 7 x 7m .The MPTs were planted between rows of coconut at a spacing of 2.33 m. The observation on soil physico-chemical properties of soil was made during 2004-2006 period. MPTs had tremendously increased the water holding capacity and infiltration rate of the soil. Ailanthus interplanted plots showed higher water holding capacity (77 .80%) and infiltration capacity (18.5 cm h ^-1) of the soil. Coconut plots interplanted with casuarina showed lower soil pH (4.9) values compared to sole-coconut plot while highest pH was recorded in sole coconut plot. Agroforestry practices considerably increased the organic carbon content of the soil (were 1.52% instead of 0.65% in control). Leucaena interplanted plots shown higher concentration of available N (203.64 ppm) while, Casuarina interplanted plots showed higher available P (9.85 ppm), available K (66.18 ppm) and the surface layer had more concentration of available nutrients. As the soil depth increases the available nutrient concentration was found to decrease. Results of the study confirms the complementary effect of MPTs in improving the physico-chemical properties of soils.