Effect of elemental sulphur and compost on pH, electrical conductivity and phosphorus availability of one clay soil
Suitable plant nutrition is one of the most important factors in the quantity and quality of crops’ yield. In plant nutrition, each nutrient should be in adequate level. The most important role of pH is the control of nutrients solubility in soil. Nutrient availability usually decreases with increasing pH. Experimental soil sample was collected from 0 to 30 cm depth from Niar village around the Ardabil city.The soil samples were mixed with solid acidifying material including elemental sulphur (S) in three levels (0.25, 0.5 and 1.0 g/kg soil), farm yard compost manure in three levels (2.5, 5 and 10 g/kg soil) and elemental S + organic matter in three levels (the same amounts of S with 5 g/kg cattle manure), and filled in 4 L pots. Soil water content was held close to field capacity and green house temperature was kept to 25 ± 5°C. Before the experiment, the physicochemical properties of soil and chemical properties of the compost were measured. At eight, 16 and 32 weeks of incubation, compound soil samples were collected from pots, and their pH, electrical conductivity (EC) and phosphorus (P) were measured. The results show that the effect of elemental S were obtained in the early period of incubation (28 days), but after that, only the 3rd level of S had a significant effect on pH reduction. Compost *S treatment had minor effect on pH reduction in the early stages of incubation, but markedly decreased the pH after 56 days. The effect of compost *S treatment on the pH of soil was shorter than that of S treatment and after 16 weeks, the pH of soil was increased. The effect of different compost levels on pH reduction was not significant at eight and 16 weeks when compared to the control; however, these treatments increased the pH of soil at 32 weeks. All rates of compost *S treatments caused significant increase of soil pH at 32 weeks, but S treatment had no significant difference on the control. S and S* compost treatments significantly increased the EC of soil during the experimental period, but the effect of compost on the elevation of EC was observed after 32 weeks. Available P of soil was improved in all treatments and it reached maximum level at eight weeks, and then decreased.
Key words: Sulphur, compost, soil, pH, electrical conductivity, phosphorus.