Potassium fixation of different soil types and nutrient levels

Potassium (K) fixation plays a significant role in the soil-plant system influencing the effectiveness of fertilization. Among the factors controlling fixation capacity of soils, clay mineralogy and soil moisture are of primary importance. The objective of this experiment was to study tbe K fixation capacity of different soil types and K levels as well as to develop quantitative relationships between amounts of exchangeable K and fixation under wet and dry conditions. Soil samples were collected from seven sites of national multi-location long-term fertilization trials representing different soil properties and K levels (i.e. clay content, clay minerals, and plant-available K). At higher K fertilizer rates, exchangeable K was higher, and as a consequence, lower wet K fixation capacities were obtained. On the other band, higher values in dry fixation of K were observed with higher K fertilizer rates. A good correlation was obtained between dry K fixation capacity of the soils and ammonium acetate-exchangeable K in soils having more than 20% clay. By contrast, a lower correlation was obtained between wet and dry fixation capacities. Relationships between clay mineralogy and fixation capacities were also studied in this experiment.