Effects of Long-Term Application of Sulfur-Containing and Chloride-Containing Chemical Fertilizers on Rice Yield and Its Components

Impacts of 33-yr of application of S-containing and Cl-containing chemical fertilizers on rice (Oryza sativa L.) yield and its components were investigated in a red paddy field experiment, south China. The treatments included: 1) adding 302 kg SO42−-S ha−1 yr−1 with application of (NH4)2SO4, K2SO4, and calcium superphosphate (SO42−); 2) adding 56 kg SO42−-S and 176 kg Cl ha−1 yr−1 with application of urea, calcium superphosphate, and KCl (Cl−+SO42−); 3) adding 516 kg Cl ha−1 yr−1 with application of NH4Cl, KCl, and KH2PO4 (Cl−). Under each treatment, the applied N, P, and K nutrients were controlled at conventional rates of 150 kg N ha−1 yr−1, 75 kg P2O5 ha−1 yr−1, 225 kg K2O ha−1 yr−1, respectively. Under the S-containing fertilizer application, soil SO42−-S content showed a first increasing then decreasing trend with years, and was significantly negatively correlated with annual rice yield. Average annual yield significantly declined in an order of Cl−, Cl−+SO42−, and SO42−. Under the Cl− treatment, soil SO42−-S content was maintained at about 26.5 mg kg−1, not showing deficiency. From 1990 to 2000, rice yield declined rapidly under the SO42− treatment, and was significantly lower than that under the Cl− treatment. After then, there was no significant difference in yield among the treatments. Our results demonstrated that long-term application of S-containing fertilizer could result in excessive accumulation of SO42−-S in the red paddy soils of south China, therefore producing a certain threat to rice growth. The Cl-containing fertilizer could be relatively safe.