A laboratory experiment was conducted to evaluate the effects of water soluble plant extracts on soil acidity. The plant materials were: black oat, oil seed radish, white and blue lupin, gray and dwarf mucuna, Crotalaria spectabilis and C. breviflora, millet, pigeon pea, star grass, mato grosso grass, coffee leaves, sugar cane leaves, rice straw, and wheat straw. Plant extracts were added on soil surface in a PVC soil column at a rate of 1.0 ml min-1. Both soil and drainage water were analyzed for pH, Ca, Al, and K. Plant extracts applied on the soil surface increased soil pH, exchangeable Ca ex and Kex and decreased Al ex. Oil seed radish, black oat, and blue lupin were the best and millet the worst materials to alleviate soil acidity. Oil seed radish markedly increased Al in the drainage water. Chemical changes were associated with the concentrations of basic cations in the plant extract: the higher the concentration the greater the effects in alleviating soil acidity.
Plant residue; organic material; leaching
