Sustainable cashew plantation management on weathered tropical soils through biomass and nutrient cycling

Understanding biomass decomposition and nutrient cycling in tree plantations is crucial for evaluating their impact on soil health and advancing environmental sustainability practices in tropical agroecosystems. By analysing the decomposition of leaf litter and other organic materials, we aim to understand how these processes contribute to nutrient availability and sustainability. This study evaluates the biomass accumulation, nutrient uptake, and cycling dynamics in cashew (Anacardium occidentale L.) in monoculture plantations established on weathered tropical soils over 25 years at Puttur, India. Findings revealed a substantial increase in total above-ground biomass from 0.44 tonnes per hectare (t ha⁻¹) in the first year to 58.78 t ha⁻¹ by year 25. Similarly, root biomass increased significantly, with coarse roots growing from 0.12 t ha⁻¹ to 10.18 t ha⁻¹ and fine roots from 0.14 t ha⁻¹ to 8.19 t ha⁻¹ over the same period. Leaf and litterfall data demonstrated an upward trend in biomass with tree age, contributing to enhanced soil nutrient cycling. Weed biomass showed a declining trend as tree age increased, reflecting the competitive advantage of mature cashew trees. Cashew apple and nut yields also increased markedly, with the apple yield rising from 0.57 t ha⁻¹ to 30.11 t ha⁻¹ and nut yield from 0.08 t ha⁻¹ to 3.72 t ha⁻¹ by year 25. Nutrient analysis of various biomass components indicated significant increases in nitrogen, potassium, phosphorus, calcium, and micronutrients with tree age. The annual nutrient turnover for coarse and fine roots, leaf litter, and cashew apples showed progressive increases, underscoring the critical role of nutrient recycling in maintaining soil fertility and supporting cashew production. The findings highlight the importance of tailored nutrient management strategies to support optimal tree health and yield throughout the lifecycle of trees in the orchard.