Rates and Residual Effects of Potassium Fertilization in a Brazilian Soil

IPNI-2010-BRA-56

29 Apr 2016

2015 Annual Interpretive Summary


Potassium is responsible for several vital mechanisms for plant development (e.g., enzyme activation, translocation and stock of compounds, osmotic regulation, water maintenance, etc.) and high yields. Potassium fertilizers are essential for balanced plant nutrition in the acid soils of the tropics, including Brazil. In many areas, farmers are cutting back on fertilizer expenses, which could compromise crop yields, profits, and food security in the future. The main objective of the study is to verify the effects of cutting back K fertilizer rates in some Brazilian soils. The study is also looking at other important factors that may impact the effectiveness of K fertilizer in tropical soils (i.e., P, lime, 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 of last season (sixth year of the project) showed: 1) soybean yield has not shown any significant decrease yet, but the second maize crop yield has shown significant decrease after two years of K suppression; 2) soybean and second maize crop yield have already shown great response to K application, while the second maize crop yield also shows a great negative response to curve K suppression; 3) use of phosphogypsum in the soil improves second maize crop yield with K application; 4) results indicate that the best time to apply K is at soybean seeding time; 5) the lime application effect on K response still needs more evaluation; 6) the effect of suppression of P on crop yields still needs more evaluation, and (7) results have not showed continuous effect of K placement at regular practices on crop yields. Project will continue in 2016.