Soil Chemical Properties as Affected by Six Crop Rotation Sequences and Four Residue Levels.

Crop rotations with residue incorporation can be beneficial to the sustainability of agriculture, however as long-term studies are required to determine effects on soil properties, farmers usually don't practice crop rotations. The objective of this study was to evaluate the effects of crop rotations with residue incorporation (0%, 50%, 100%, and 200%) on soil chemical properties of a volcanic soil after 4 years of cultivation. The evaluated rotations were canola (Brassica napus L.)-bread wheat (Triticum aestivum L.), canola-durum wheat (Triticum turgidum L.), canola-corn (Zea mays L.), bean (Phaseolus vulgaris L.)-bread wheat, bean-durum wheat, and bean-corn. The experiment consisted of six crop rotations, four levels of residue incorporation, and four replicates, analyzed as split-plot design. Samples were taken from the topsoil, and the following soil chemical properties were evaluated: pH, organic matter, electrical conductivity, nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), aluminum (Al), and sulfur (S). The results showed that crop rotations affected all the chemical properties evaluated, whereas the level of residue incorporation only affected the concentrations of exchangeable Mg and K. Most of the evaluated crops rotations had beneficial effects on the soil properties. The canola-durum wheat crop rotation recorded the lowest values in OM, available N and the exchangeable Ca, Mg, and Na. Exchangeable Mg and K had a directly proportional relationship with the level of residue incorporation. In conclusion, the incorporation of residues in different doses during 4 years of crop rotation in this volcanic soil had little effect on its chemical properties. [ABSTRACT FROM AUTHOR]