Low Soil Phosphorus and Potassium Limit Soybean Grain Yield in Ohio

Core Ideas Twenty‐one percent of the soil samples were within the build‐up range for P. Twenty‐three percent of the soil samples were within the build‐up range for K. Soybean yield decreased when soil test P and K were within the build‐up range. A soil survey was conducted in Ohio with the following objectives: (i) to assess the status of soil fertility; (ii) to examine soybean grain yield in areas with fertility levels in the build‐up range, where soil test levels were less than the critical level (CL); the maintenance range, where soil test levels were between the CL and maintenance limit (ML); and the drawdown range, where soil test levels were greater than the ML; and (iii) to determine if the soil test and yield data collected support the state‐established fertility recommendations. Soil sampling was conducted from 2013 through 2015 resulting in 593 total samples. Soil P, K, Ca, Mg; pH; organic matter (OM); and cation exchange capacity (CEC) were measured. Soybean grain yield was also collected from the sampling areas. Twenty‐one and 23% of the soil samples collected were within the build‐up range for P and K, respectively. On average, grain yield was 7 bu/acre lower in sampling areas associated with soil P levels in the build‐up range, whereas an average grain yield reduction of 4 bu/acre was associated with K levels in the build‐up range. In sampling areas, there was no difference in grain yield associated with soil P and K levels within the maintenance range and drawdown range. Our data suggest that soil test levels within the build‐up range were associated with lower soybean grain yields.