Optimum Levels of Sulphur and Zinc for Rice in Lowland Areas of Kilombero District, Tanzania

Two on-farm experiments were carried out from January to May of 2014 and 2015 at Mkula, Mbasa and Kisawasawa sites to establish optimum rates of sulphur (S) and zinc (Zn) for rice production in Kilombero district, Tanzania. The treatments tested were: an absolute control and a control for N in both of the experiments. The other treatments for S experiment were a control for S, and sulphur rates of either 10 or 20 kg S ha-1. The second experiment testing Zn had treatments: a control for Zn, Zn rates of either 2.5 or 5.0 kg ha-1. All treatments other than the absolute control received all other limiting nutrients at adequate rates. The test crop was rice variety SARO-5. The results indicated that S application increased grain yield (GY) by 1.8, 2.8 and 1.8 t ha-1 at Mbasa, Mkula and Kisawasawa, respectively. The shoot S concentration increased from 0.13 to 0.29; 0.13 to 0.24 and 0.16 to 0.22% at Mbasa, Mkula and Kisawasawa, respectively. Zinc application increased yield significantly only at Mbasa site by 2.8 t ha-1 and shoot-Zn concentration from 11.5 to 27.0 mg kg-1. The optimum rate of sulphur at Mbasa and Kisawasawa was 10 kg S ha-1 and 20 kg ha-1 at Mkula site. For zinc, the optimum rate at Mbasa site was 2.5 kg Zn ha-1. It was concluded that sulphur application was needed in all the test sites to optimize yield while Zn was needed only at one site (Mbasa).