Effectiveness of coir dust and rubber latex based slow release fertilizer on the growth of immature rubber (Hevea) and soil nutrient availability

Slow release type of fertilizers (SRF)enhance nutrient retention in soil, increase fertilizer use efficiency and mitigate environmental problems. As such techniques, this study examined the influence of encapsulated coir bricks (ECB) on the growth of immature Hevea plants at field conditions. Single application of two types of ECB;ECB type 1 and ECB type 2 which were produced by using different quantities of inorganic fertilizers with filling mediums were evaluated against the conventional type of four split applications. Plant diameter was measured at 6 months after planting and plant girth was measured at 12 and 18 months after planting. Leaf nutrients, soil nutrients and soil pH were measured at 18 months after planting. Application of two types of ECB and conventional type of fertilizer gave almost identical growth performances; with reference to plant diameter and girth. Moreover, ECB type 2 recorded the highest plant diameter at 6 months after planting (1.65 cm) and plant girth at 12 months after planting (10.545 cm) and 18 months after planting (14.81 cm) even though not shown significant differences among treatments. Leaf macro nutrients; N, P, K, Mg and soil total N, available P, exchangeable Ca and pH values were also comparable. Significantly higher exchangeable soil K values were observed with ECB applications over the conventional type fertilizer application. Moreover, the highest available soil P (26.4 ppm), exchangeable K (168 ppm), exchangeable Ca (258 ppm) and Mg (31.72 ppm) could be observed with SRF applications. On the above ground, there is a possibility of using single application of both types of ECB as a substitute for four split applications of conventional fertilizers recommended for immature rubber plants.