Organic Composition of Green Manure During Growth and Its Effect on Cation Mobilization in an Acid Oxisol

Shoot samples of oil seed radish and black oat were collected during the winter at 60, 75, 90, and 120 days after planting (dap). At each cutting organic composition of the water soluble fraction (WSF) was determined and its effects on the mobilization of cations in acid soil were evaluated using PVC soil columns. A biological test based in root growth of pre-germinated wheat seeds was conducted for 7 days in soil columns after application of the WSF of plant materials. The relative organic composition of the plant materials changed between cutting times and the greatest values were observed at 60 dap for oil seed radish and 75 dap for black oat. In the later sampling dates, the relative values were decreased sharply. The identified organic compounds were aliphatic and phenolic organic acids. The application of the plant extracts in soil columns increased the pH and the concentrations of exchangeable calcium (Ca), magnesium (Mg), and potassium (K), and decreased exchangeable Al. Few differences between pl...