Abstract
Aims
Production of high yielding forage grasses on the extensive areas of tropical sandy soils in the Lower Mekong Basin is constrained by acidity, low soil nutrient concentrations, and potassium and sulfur depletion, limiting the ability of rural households in the region to meet the economic opportunities arising from the growing demand for livestock products in Asia. This research aimed to measure the response of forages grown in sandy soils that were provided with additional potassium sulfur, and lime inputs. It was hypothesized that additional potassium, sulfur and lime above local recommendations would increase biomass production and soil organic carbon concentrations.
Methods
An experiment was conducted over two years in the Lao PDR to compare the response and soil organic carbon accumulation of forage grasses grown in sandy soils that were either managed according to recommended fertilizer and manure additions, or provided with additional potassium and sulfur at four different rates, and lime.
Results
Yield increases of 25% were achieved with additional K and S but benefits were conditional on season and variety. Soil organic carbon concentration in the top 5 cm increased by up to 1.38 t ha−1 with forage production.
Conclusions
High yielding forages are likely to become limited by soil potassium. The imbalance of supplied nitrogen relative to potassium highlights inefficiencies in the recommended rates relative to forage production requirements, demonstrating potential to improve productivity and reduce nitrogenous waste. Increases in organic carbon stocks indicate the potential for improved forages to provide environment benefits.
