Abstract:

Sulphur(S) is an essential nutrient required for all living organism. Over the last two decades, many regions in the world have a fundamental shift in the S balance toward deficit in agricultural systems for several reasons. High analysis N and P fertilizers have gradually replaced traditional ones that contain S. In addition, yields of agricultural crops have increased markedly, and in some cases more than doubled, resulting in increased removal of nutrients, including S from soils, and so on. Although wheat has a relatively low requirement for S, deficiency of S in wheat growth has been observed in many regions in China. Apart form the clear effects on crop growth and grain yield, crop S nutrition can also exert a large influence on the quality of wheat. Previous studies focused on effects of S fertilizer on leaf net photosynthesis (Pn) and yield of wheat. This paper aims to compare the effects of different S fertilizer treatments on leaf photosynthesis characteristics and grain yield of both multi-spike（Yumai 49）and large-spike（Yumai 66）wheat cultivars. The results would help characterize the photosynthetic mechanism for changed grain yield under sulphur application and improve fertilizer strategy in modern wheat production systems in China. Experiment was conducted with soil available sulphur content of 15.8 mg.kg^-1 in 2001/2002 and 2002/2003 growing seasons. A total of eight fertilization treatments were implemented, i.e. no S fertilizer(C1S0,C2S0), 60 kg.ha^-1 S for base application(C1SI,C2S1), 120 kg.ha^-1 S for base application (C1S2,C2S2) and 60 kg.ha^-1 S for base application and topdressing at Jointing stage in 5:5 ratio(C1S3,C2S3). The results indicated that comparing with S0, photosynthesis traits of all the treatments with sulphur fertilizer were increased. Canopy apparent photosynthesis (CAP) and flag leaf’s chlorophyll (Chl) content with the treatment of sulphur application of both the cultivars were obvious higher than their respective control in filling stage(Fig.1, Fig.3), meanwhile flag leaf net photosynthesis (P_n) was significantly increased, and exhibited slower decline at the late grain filling stage（Fig.2）. The increasing of flag leaf transpiration (T_r) expressed strong potential of physiological metabolism of treatments with sulphur fertilizer(Fig.4). There was the same trend in the change of leaf photosynthesis characteristics in both cultivars and Yumai 66 showed obvious dominance in CAP and Pn in filling stage. The grain yields in treatments of sulphur application were higher than those in no sulphur fertilizer , and S3 of Yumai 49 and S1 and S3 of Yumai 66 were significantly different from the control at the 0.01 probability level（Table 1 and 2）,which resulted from increasing 1000-kernel weight and No. of spikes respectively. The treatment of 60 kg.ha^-1 sulphur for base application and topdressing at Jointing stage in 5∶5 ratio showed the best effects. With treatment of no S and 120 kg.ha^-1 S for base application, CAP, P_n, Tr and Chl content were lower ,which resulted probably from the unbalanced nutrients in soil due to the improper input of nutrients which were responsible for the fast declining of flag leaf and canopy photosynthesis characteristics during grain filling. Some suggestions of sulphur fertilizer rational application were also put forward in winter wheat cultivation.

Key words: Sulphur fertilizer, Winter wheat(Triticum aestivum L.), Photosynthesis characteristics, Yield