---Do you know tthe critical level of potassium for soybean?

Question

which amount of potassium we can use for soybean in different soils?

Answer 1

The objective of this project is to enhance our mechanistic understanding of factors and processes that govern K fluxes in the soil and improve our ability to predict the amount of fertilizer K required on a soil-specific basis. Five field sites were established at regional Purdue Agricultural Centers, along with one site in northwest Ohio. Each had an initial soil test level (whole field average) at or below the critical level for potassium. The soils represented groups of major agronomic importance. The cropping system is a corn and soybeans rotation, with both crops present in each year. The K rates are annual additions of K (0, 36, 72, 145, and 217 lbs K2O/A) or biennial K additions (0, 72, 145, 217, 434 lbs K2O/A) with K applied for the full two year rotation before either corn or soybeans. Initial exchangeable K soil test levels (0-4 in) were higher than expected. The laboratory analysis of soil K, including exchangeable and non-exchangeable K (tetraphenylboron extractable), and plant K accumulation is ongoing. Across sites, there has been a significant corn yield response to K, but soybean yields did not respond to K in any site year. This project is developing a well-documented set of nutrient uptake and soil test calibration data which should prove valuable in assessing soil test and recommendation procedures for several major Midwest soil types.