Rock Powder Can Improve Vermicompost Chemical Properties and Plant Nutrition: an On-farm Experiment

Together with farmers, we evaluated nutrient availability from vermicomposted gneiss powder, assessed its influence on growth promotion, nutrition and heavy metal accumulation in maize plants and the effect on soil chemical properties in the field. Three soil treatments were applied: fertilization with vermicompost with gneiss powder, fertilization with vermicompost without gneiss powder, and soil without fertilization (control), in a randomized block design with five replicates. The dry weight of shoots and the concentrations of potassium, calcium, magnesium, manganese, nickel, chrome and lead in the dry matter of maize were higher with vermicompost with gneiss powder. In the soil, the potential of hydrogen and phosphorus, potassium and calcium concentrations were higher with vermicompost with gneiss. There were no detectable levels of heavy metal wastes in the soil after the experiment. We conclude that vermicomposted gneiss powder has potential for use in agriculture as a nutrient source and can improve soil chemical properties.