The influence of crop residues in vertical soil mobility of potassium

This study has been developed to evaluate the influence of applying different types and doses of crop residues on potassium (K) mobility in soil columns. Rhodic Haplustox samples were collected at depths of 0.0-0.10, 0.10-0.20 and 0.20-0.30 m and used to create such soil columns, keeping the same profile distribution. The experimental design was randomized with three replications and the treatments resulted in a 4x4 factorial design, 4 types of crop residues (brachiaria+sunflower; Mix (cultivated radish+oat+winter vetch); cultivated radish and wheat) and 4 doses of residues (0, 10, 15, and 20 Mg ha-1). The grinded and dried residues were applied to the surface of the columns, which were then irrigated with distilled water and incubated for 10 days to stabilize the reactions. After incubation, the soil columns were disassembled and separated into 0.05 m layers (0.0-0.05, 0.05-0.10, 0.10-0.15, 0.15-0.20, 0.20-0.25 and 0.25-0.30 m). The samples of each layer were dried, sieved and analyzed to determine the amount of exchangeable K. The results obtained indicated that surface application of crop residues alters soil levels of exchangeable potassium, especially in the 0.0-0.05 m layer. Increases in residue doses may cause a significant and linear increase in exchangeable K content in the 0.0-0.05, 0.05-0.10 and 0.10-0.15 m soil layers. Superficial application of residues of cultivated radish and Mix produced the largest increases in levels of exchangeable K, reaching depths of 0.30 m. Increases in potassium adsorption in the soil surface layers reduces the need for potassium fertilization and can reduce production costs and environmental pollution