Exploration of Responses to Potassium in Western Uruguay

Several regions of Uruguay has recently shown K deficiencies and responses. This project looks to determine the different areas with K deficiency, evaluate responses in the main field crops, and provide information on K soil testing.


29 Sep 2017

Research with impact - Documenting the Need for Potassium in Uruguay

La Manera 2014/15; with K in front, without K in the back

Agriculture in Uruguay initially developed in high potassium (K) soils, under conventional tillage and crop rotations that required no K fertilizer. The scenario changed during the last decades driven by increasing grain prices. The annual cropped area tripled between 2002 and 2014, with soybean now sown on 67% of the area. Cropping systems have intensified, shifting from crop-pasture rotations to continuous annual cropping under no-till cultivation. The K balances in Uruguay (application minus removal) are negative due to the absence of K fertilization. As soybean production increases, the K balance becomes more negative. In addition, agriculture has expanded into marginal soils that are already low in K.
IPNI supported several experiments through a joint project with the Faculty of Agronomy (UdelaR), INIA, and other Uruguayan institutions and with the partial support of Canpotex to identify the need for additional K fertilizer through improved calibration of soil test analysis. Field studies between 2007 and 2014 found a response to K fertilizer in 32 of 110 sites. These studies support a critical soil K concentration range of 120 to 160 ppm as a guide to defining the need for additional fertilizer.
However, the scatter plot shows a wide range in predicted K response, which highlights a need for further site-specific research. These studies represent a breakthrough in fertilizer research in Uruguay, demonstrating the need
for K in many cropping systems. Fields that were responsive to K fertilizer averaged 66% higher yields for maize, 37% for barley, 12% for wheat, and 10% for soybean, compared to plots that omitted K.
These results have largely contributed to the increase in annual K2O imports to Uruguay, rising from 9,000 t in 2003 to 146,000 t in 2013.

Additional Resources

Documenting the Need for Potassium in UruguaySize: 2.35 MB