Influence of sulphur fertilizer placement, soil moisture and temperature on yield response of rape to sulphur-bentonite

Experiments were conducted in the glasshouse to determine the effect of placement of S-bentonite fertilizer either on the surface of the soil or to a 5-cm depth at the time of planting on yield response of rape. Included in the experiments was a combination of two soil moisture regimes (wet, between field capacity and one third available soil moisture; and dry, between field capacity and 2% above wilting point) and two soil temperatures, 14 and 17°C maintained by thermostatically controlled water baths. Results of the initial experiment conducted over 42 days showed that elemental S did not increase the yield of rape beyond the control and that ammonium sulphate fertilizer (used as the S fertilizer standard) increased the yield dramatically. Observations in later experiments indicated that the S prills did not readily disperse in the soil when wetted with water and that physical break up of the prills was required if the fertilizer was to be oxidized to the SO4 state in time to be beneficial to an annual crop of rape.