Losses of Soil Potassium

Potassium losses are caused by:

1. Crop removal

2. Fixation

3. Leaching

Fixation and leaching are not serious problems for Nebraska soils. As was previously discussed, fixation can result in temporary “tie-up” of potassium. Over a period of time, however, potassium eventually becomes available. Leaching is not a problem on silt and loam soils, but can be a problem on sandy soils.

By far, crop removal accounts for the largest loss of potassium from soil. In general, potassium content of grain is less than straw or stover. Corn cut for silage would remove about 195 pounds of potassium per acre. Much of this could be returned in the form of animal manure applications from the livestock operation. Corn harvested for grain would leave the stover in the field; and, since potassium is water soluble, it would be quickly returned to the soil. Table 6.3 shows rates of potassium removal for common crops grown in Nebraska.

Crop Yield K2O Removed (pounds/acre)
Corn 150 bushels/acre 35
Grain stover 6300 bushels/acre 160
Wheat 60 bushels/acre 15
Grain straw 5000 bushels/acre 90
Soybean 50 bushels/acre 70
Alfalfa 4 tons/acre 100

Table 6.3.  Average Removal of Potassium by Crop Production