RESUMO
Incubation experiment was established under laboratory conditions on alluvial soil from south Giza Governorate to evaluate the effect of sulphur and organic manure on thiosulphate efficiency as a nitrification inhibitor. Ammonium sulphate and urea were applied as nitrogen sources, in addition to sodium thiosulphate and sulphur at rate of 100 mg Kg[-1] soil in mixture form with soil and organic manure at rate of 2%. Moisture was maintend at 80% of water holding capacity. Soil sample were taken every week for determination of soil acidity, ammonium, nitrate and thiosulphate concentrations. The obtained results indicated that thiosulphate alone delayed turnover of urea and Ammonium to nitrate and thus decreased soil pH. Ammonium sulphate treatment was more effective than urea one. Similar trend was noticd with a mixture of thiosulphate, sulphur and organic manure but it was more significant than thiosulphate alone. This effect can be noticed from NH[4]/NO[3] ratios which were higher in case of the mixture as compared to thiosulphate alone. The opposite relationship was observed between thiosulphate concentration in soil and nitrate release, where, it showed more significant effect by using the mixture of thiosulphate, sulphur and organic manure than as compared when thiosulphate alone was used