Fertilizer sources were urea, treble superphosphate, monoammonium phosphate, potassium chloride, potassium nitrate, and ammonium chloride. Plot size was six rows wide and 20 feet long. Locations were characterized by standard soil analyses. Ammonium acetate extractable K was determined from 0-6 inch soil samples. Grain yield responses to K and Cl fertilization and associated K and Cl soil analyses are shown in Table 1.
Response refers to the difference between appropriate treatment means.
Most of the experiments were conducted on a conventional alternate crop-fallow cropping system. Yield responses were averaged by location and analyzed by a t-test. As indicated in Table 1, K or Cl response in these studies was not predictable by soil analyses. Plant analysis may be a better indicator of spring wheat Cl status. Research from other locations in Montana and other states had found soil and plant analysis as useful indicators of K and Cl response.