Exploration of Responses to Potassium in Western Uruguay

This research is partly based on previous observations of K deficiency and responses in field crops grown within the northwestern Uruguay region. Field experiments in the first 3 years of this study (2006/07, 2007/08, and 2009/10) have also showed significant responses to K fertilization.

Data from the first 3 years of field work and other studies, including 50 experiments under wheat, barley, maize, soybean, sunflower, or sorghum, were compiled to evaluate the relationship between relative yield and soil exchangeable K (0 to 20 cm). A critical range of 0.33 to 0.50 cmol/kg (129 to 195 ppm) was estimated, below which there is a high probability of response to K fertilization. Integration of soil survey data with this field work has allowed researchers to estimate that 4 million ha have the potential for soil K deficiency in northwestern Uruguay.

Field work in 2009/10 evaluated the residual effects of K fertilization in the previous year on soybean grain yields. Five of 13 experiments showed significant yield responses to residual K fertilization. Grain yield responses averaged 247 kg/ha in sites with soil exchangeable levels below 0.35 cmol/kg (136 ppm). On-going studies are looking at the dynamics of K release from crop residues, the K buffering capacity of different agricultural soils, and the temporal variation of soil exchangeable K under contrasting management. Uruguay-02