ASSESSING DECOMPOSITION RATES AND NUTRIENT RELEASE FROM VARIOUS ORGANIC MATERIALS IN PINEAPPLE CULTIVATION

Abstract

Deteriorating soil fertility remains a persistent issue affecting agricultural production in Kalutara, a wet zone in Sri Lanka. Using heavy amounts of synthetic fertilizer to enrich soil fertility is harmful to the environment. Therefore, finding alternative, more sustainable, and cost-effective organic nutrient management systems is vital. This study was designed to assess the decomposition dynamics and nutrient release patterns of various organic matters (OMs) through a litter bag experiment conducted in pineapple cultivation. The four different organic matters; Gliricidia (G), Compost (C), Cattle manure (CM), and Poultry manure (PM) were used as treatments. The experiment was arranged in a Randomized Complete Block Design (RCBD) with 3 replicates. Decomposition rate (remaining dry mass after 16 weeks of decay) and the release of certain macronutrients [nitrogen (N), phosphorous (P), potassium (K)] and micronutrients [zinc (Zn) and manganese (Mn)] were analysed. After 16 weeks of the study, the results revealed the significantly highest decomposition rate (0.12±0.007 g week-1) with Gliricidia compared to other OMs (p<0.05). The order of decomposition for OM were shown as G>PM=CM=C. From the nutrient analysis, the significantly (p<0.05) highest release of P (5.76±0.4%), and K (0.10±0.01%) were recorded with PM showed simultaneously the highest (p<0.05) release in Zn (0.09±0.001%) and Mn (0.08±0.002%). However, the significantly highest N (13.57±0.6%) was released with Gliricidia compared with other OMs (p<0.05). Overall, it can be concluded that PM is highly effective as OM for nutrient release for many tested nutrients, however, it exhibits limitations in releasing N with lower decomposition. Hence, future studies will be essential to enhance the decomposition rate of PM, making it a viable alternative source for cultivating pineapples.