Assessment of Soil Potassium Supplying Capacity from Soil Nutrient Reserves and Dissemination of Nutrient Management Technologies through Nutrient Manager

The current project was initiated to estimate, through a plant-based assay, the magnitude and variation in soil K supplying capacity across a range of soils with varying soil properties in Bangladesh. This will help develop soil-based coefficients (e.g., soil K supplying capacity, K draw down factor, etc.), which can be used with Nutrient Manager, a field-specific nutrient recommendation tool developed by the International Rice Research Institute (IRRI), in the determination of fertilizer K requirements for rice and maize.

In the first phase of the study, representative soil samples from diverse locations are being collected throughout Bangladesh to represent a diversity of mineralogy and properties suspected to be related to soil K supplying capacity. The samples will be analyzed for non-exchangeable, exchangeable, and total (solution) K concentrations. After analysis, 15 samples ranging from high K reserves to severely K deficiency will be selected for pot experiments. Rice will be grown to the booting stage and maize will be grown to V8 stage before biomass harvest. After harvest, the soil in each pot will be mixed and another crop will be grown. This will be repeated for about 6 to 8 crop cycles without the application of K. Results of the pot studies and subsequent field experiments will be utilized to develop field-specific nutrient recommendation tools to facilitate on-farm application of site-specific K recommendations in rice and maize. The first year’s work of the project also facilitated the cooperation between scientists in Bangladesh and IRRI to further develop site-specific K recommendation principles for integration within their decision support tool. Bangladesh 006