Behaviour of Different Levels and Grades of Diatomite as Silicon Source in Acidic and Alkaline Soils

Diatomite or Diatomaceous earth (DE) is a sedimentary rock that results from the deposition of Si rich unicellular life forms (diatoms) found in both salt and fresh water. The cell walls of these dead diatoms consist of amorphous silica. Amorphous silica is more easily solubilised than crystalline silica and is expected to release more PAS (Plant available silicon). Information on use of DE as the source of Si in different crops is very limited and hence there is a need to know the effect of different levels and grades of DE on availability of nutrients in acidic and alkaline soil under field capacity and submergence level. An incubation study was conducted by using acidic and alkaline soil in a plastic pot with different levels (0, 150, 300 and 600 kg ha (-1)) of diatomite under field capacity and submergence. In another study, five different grades of diatomite at different levels (0, 250, 500, 750, 1000 and 1500 kg ha (-1)) were incubated under the field capacity moisture regime alone. During the incubation studies, soil samples were periodically analyzed for pH and PAS at 7, 15, 30, 60, 90 and 120 days after incubation (DAI). Increase in pH of acidic and decrease in pH of alkaline soil was recorded irrespective of application rates of diatomite under both the moisture regimes. Increase in PAS was observed at 30 DAI in both types of soil. Among the different grades, diatomite-3 and diatomite-4 recorded significantly higher PAS in acidic soil under the field capacity moisture regime.