Effects of different dose of sulfur fertilizer on photosynthetic characteristics and grain yield in winter wheat

Although Sulfur is one of the essential nutrients for plant growth, it hasn't had attention for many years (because) S-containing macro-nutrients fertilizers and atmospheric inputs supplied adequate S into soils. However, more and more reports showed that crops suffer the S deficiencies over the past several years. It was caused by massive (application) of high concentrated macro nutrients fertilizers with free or low S, S being removed due to high productivity varieties and intensive agriculture, less use S containing pesticides, and reduced atmospheric inputs caused by stricter (emission) regulations. Wheat is one of the most widely cultivated crops in the world. Although it has a relatively low S (requirement,) S deficiencies on wheat have been observed in many countries. Proper sulfur level not only could meet the needs of wheat growth, but also assures the fitting S-contained amino acid in wheat seeds. The effects of sulfur on the physiological processes such as photosynthetic characteristic were studied in this paper.In order to clarify the effects of sulfur fertilizer on photosynthetic characteristics and grain yield in winter wheat, a field experiment was conducted with two winter wheat (Triticum aestivum L.) cultivars 8901-11(A) and 4185(B) on the Teaching and Demonstration Farm, Agricultural University of Hebei, Baoding, during 20012002. The experiment was arranged by split plot design including four treatments being S 0, 30, 60 and 90 kg per hm2 with three replications. The net photosynthetic rate(Pn), chlorophyll content(Chl), soluble protein content(Pr) during growing period, and grain yield and yield components after harvest were determined, separately. The results showed that, in the scope of sulfur (application) (S 060 (kg/hm2)), Pn, Chl and Pr of top leaves in each growth period, flag leaf and the third leaf all (increased) along with the increase of sulfur fertilization application. For high sulfur treatment (S 90 (kg/hm2)), the P_n and Chl and Pr for all leaves were lower than those of middle sulfur treatment (S 60 (kg/hm2)), which had the highest gain yield. Those indicated that fertilizing more than S 60 (kg/hm2) might have negative effect on photosynthetic capability (under) the condition of the trial soil (soil available S 10 (mg/kg)). The changing tendency of unit area spike, grain number per spike and 1000-grain weight, are also consistent along with same tendency. It could be concluded that reasonable sulfur fertilization improved photosynthetic capacity of wheat, which might be the physiological basis of the grain yield (increase) caused by S fertilizing. Synthetically considering the effects of sulfur on photosynthetic capacity and grain (yield,) the dose of recommended sulfur fertilization is S 60 (kg/hm2) under the condition of soil available S being10 (mg/kg).