Rates and Residual Effects of Potassium Fertilization in a Brazilian Soil

IPNI-2010-BRA-56

25 Mar 2014

2013 Annual Interpretive Summary


Potassium is responsible for several vital functions for plant development (enzyme activation, translocation and stock of compounds, osmotic regulation, water maintenance etc.) and high yields. Potassium fertilization is essential for balanced plant nutrition in the acid soils of the tropics, including in Brazil. In many areas farmers are cutting back on fertilizer expenses, which could compromise good yields, profits and food security in the future. The main objective of this study is to verify the effects of reducing K fertilizer rates in some Brazilian soils. The study is also looking at some other important factors that may affect the effectiveness of K fertilizer in tropical soils (e.g., applications of P, lime, and phosphogypsum, time of application and locality effects) to evaluate their effects on soil K status with time, plant K status with time and grain yields.

Results for the third crop season (2013) (soybean and maize second crop) indicated statistically significant response to K rates for soybean yield and K leaf content, statistically significant response to K rates for maize seed weight and plant height, statistically significant response to K rates for soil K availability, a positive effect of lime and phosphogypsum application for maize yield and plant height, and for soil pH and base saturation, effect of locality of K application for soybean K leaf content. Thus far the results are in agreement with initial expectations demonstrating the importance of an adequate K supply. The project is planned to continue for three more years.