Soil potassium level in relation to potassium treatment, season of year and soil moisture level

Soil samples on twice monthly basis were taken from six plots located on Agronomy-plant pathology South farm and five samplings from four plots located on the Agronomy Northern Experiment Station at DeKalb. Twice monthly soil samples showed that percent soil moisture content, soil acidity, field-moist and air-dry exchangeable potassium were lower in summer months and higher in winter months, while non-exchangeable potassium test levels were higher in summer months and lower in winter months. Successive extractions of the sum of six non-exchangeable potassium extractions are consistant at 30%, 20%, 15%, 13%, 11% and 9%. Exchangeable, non-exchangeable and mineral potassium are interrelated by an equilibrium and are interchangeable. Exchangeable potassium in soil samples from field plots with lower K treatment history increased with drying (air and oven), while field plots with higher K treatment history decreased over field-moist K test with different intensities. Changes with storage were detected from test made at the time of field sampling to later test in the test levels of exchangeable potassium of the air-dried soil samples over times under laboratory condition. Month-to-month least significant differences were noted for all the tests. There was no trend in the field moisture and soil acidity but a significant seasonality existed. Field-moist and air-dry K test levels are effected by seasonal cycle and trend. Plots treated with K rates alone showed more buildup levels of exchangeable potassium, while non-exchangeable K test levels increased more by K and N rates applied togather. Twice monthly variation limits the interpretative values of all tests.U of I OnlyETDs are only available to UIUC Users without author permissio