| Abstrakt: |
Studies of S deficiency, a problem in certain crops in Africa, have yielded inconclusive and incomplete information. There is little information on the S status of soil in the forest‐savanna zone. Field trials were carried out with maize (Zea maysL.) at six locations in the forest and savanna zones of western Nigeria. Sulfur was applied at 0, 7.5, 15.0, 30.0, and 60.0 kg S/ha. Significant yield increases were observed with rates of S application from 7.5 to 30 kg S/ha. The response was more distinctly evident in the savanna than in the forest zone. Silking percentage was enhanced and grain quality improved with S application. No significant residual effect of the applied S was observed in the savanna zone, which was probably due to heavy leaching of the applied S. On these soils S response was observed where the amount of extractable S, extracted with either KH2PO4, Ca(H2PO4)2, or NH4C2H3O2was below 4 ppm S. There was no response to S when extractable S levels were equal to or greater than 8.5, 10.0, and 12.0 ppm when soils were extracted with Ca(H2PO4)2, NH4C2H3O, and KH2PO4, respectively. The critical S level in the ear leaf was estimated at about 0.14% S. Although there was a strong correlation between % N and % S in the ear leaf, the N:S ratio was not related to critical S levels in plants. |
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