Effects Of Conservation Tillage On Flag Leaf Water Use Efficiency Of Winter Wheat In Oasis Irrigation Area

In order to discuss the flag leaf water use efficiency of winter wheat under different conservation tillage in Hexi irrigation district. We designed the five treatments, which were conventional tillage (T), tillage with straw returned (TIS), no-tillage (NT), no tillage with straw mulch (NTS), no tillage and stubble standing (NTSS), to study the diuranal changes and stages changes of the flag leaf water use efficiency of winter wheat and the affected factors correlated with WUE. The results showed that:1. The flag leaf water use efficiency of TIS,NTS,NTSS were higher than that of the conventional tillage except NT. The NTS,NTSS and TIS were 18.84%,51.01%,36.81% higher than T. The flag leaf water use efficiency of NT was decreased 2.32% compared to T because of its higher transpiration rate.2. The photosynthesis rate of the TIS,NT,NTS and NTSS were higher than that of T. The photosynthesis rate and transpiration rate of NT were higher than that of T, and the discrepancy of NT and T was great. So the function of flag leaf under NT was stronger, the transpiration rate rose, which could raise the photosynthesis rate. The transpiration rate of NTSS and NTS were lower than that of T, but the photosynthesis rate of them was higher than that of T. It showed that NTSS and TIS could restrain the transpiration rate of winter wheat and decrease wastage of winter.3. The water use efficiency of flag leaf under conservation tillage was lower than that of conventional tillage at heading stage. The photosynthesis rate and transpiration rate of flag leaf on conservation tillage were also higher, so their WUE were lower. The main physiological and ecological factors were stomatal conductance,intercellular CO₂,relative humidity and soil temperature which influenced the WUE of flag leaf.4. The water use efficiency of flag leaf under conservation tillage was higher than that of conventional tillage at flowering stage. The transpiration rate of leaf was the direct factor that influenced the discrepancy of WUE under different conservation tillage. The photosynthesis rates of conservation tillage were higher than that of conventional tillage, but the transpiration rate of them were lower than that of convaentional tillage except NTSS. So the WUE of flag leaf was higher under conservation tillage especially in the afternoon. The content of soil water and the leaf temperature had no advantage under conservation tillage. The soil temperature of conservation tillage decreased the photosynthesis rate and influenced the WUE of leaf. The soil temperature of conventional tillage increased transpiration rate and decreased the WUE of leaf.5. The discrepancy was not great of water use efficiency of flag leaf on all treatments at filling stage. The rule of photosynthesis rate and transpiration rate of flag leaf were similar under the same tillage. So the WUE were similar under different tillage. Because the leaf water potential was lower, which was physiological factor, the transpiration rate was higher. The soil temperature was higher, which was ecology factor, the transpiration rate was higher.6. The Pn and Tr were significantly lower than that of former stages at maturity stages. The photosynthesis rate and transpiration rate under conventional tillage were lower than that of conservation tillage because the function of flag leaf degenerated rapidly under conventional tillage. So the WUE of flag leaf was higher than conservation tillage. The stomatal conductance could decrease the WUE of flag leaf, which was main physiological factor. The soil temperature was main ecological factor, which increased the transpiration rate of leaf and decreased photosynthesis rate. So the WUE of flag leaf was decreased.7. The water use efficiency on flag leaf level and water use efficiency on yield level of winter wheat had increased under conservation tillage. The measure could increase the water use efficiency of flag leaf under different tillage by changing the small environment of farmland, in order to decrease the transpiration rate but ensured the photosynthesis rate. The conservation tillage could increase relative humidity of air and decrease the discrepancy of soil daily temperature. So they were in favor of decreasing transpiration rate.