The effect of addition of elementary sulphur (S°) on the pH and solubility of some plant nutrients was studied in fosfocomposts prepared with 1 kg water hyacinth (Eichhornia crassipes), 800 g cow manure, 200 g phosphate rock (RF) and 5 g sulphate acid soil, using Thiobacillus sp bacteria as inoculum. 0, 5, 10, 15 and 20 g of S° per 2 kg of composts were applied with two replicates each and a control without RF nor S°. After a 6 month incubation, soluble P, Mg, Ca, Fe, Cu, Mu, Su, NO3-, NH4+ and SO42-, pH, and C/N ratio were determined, as were total content of each metal and P, N, S and C. The percentages of total P and Ca were higher in the phosphocomposts than in the control, while the concentrations of N, K, Mg, Fe, Cu, Mn and Zn were higher than in the control (p<0.001). The lowest pH value was found in the phosphocompost with highest quantity of S°. A significant correlation exists between pH and SO42; the relation increases with a decrease in pH affecting negatively the decomposition of organic matter and resulting in lower soluble NO3-, P and K. A positive association was found between NO3- and pH. Ca, NH 4+, Fe, and Mn were more soluble with increasing acidity. Soluble Zn and Mg varied significantly among the composts without relation to pH. More soluble Ca with high S° was an indication of a higher dissolution of the added RF. However, available P diminished in the phosphocomposts with acid pH, possibly due to its immobilization with Fe and the low decomposition of the organic matter.
|Translated title of the contribution
|The effect of elementary sulphur on the pH and solubility of some nutrients in phosphocomposts
|Published - Sep 2003