| Studied on effects of different tillage methods on photosynthetic eco– physiological characteristics, dry matter accumulation and distribution properties and yield of spring wheat by field located experiment field in semi-arid area of the Loess Plateau, the main results showed as the following:1. The growth stages in which the different tillage methods had the greatest effect on Pn,Tr,WUE,Gs and Ci were milking, booting, milking, flowering and filling respectively. The effect of the growth stage on the Pn,Tr,WUE,Gs and Ci was greater than that under the different tillage methods. The flag leaf of the spring wheat had powerful Photosynthetic capacity under the conservative tillage methods ,compared with T, the average Pn of the other five conventional tillage methods, namely, NTS,NT,NTP,TSandTP could be improved by 8.97%,4.08%,15.17%,9.46%and 11.26% respectively, the flag leaf area, diurnal photosynthetic capacity, and diurnal photosynthetic capacity of the flag leaf per plant under conservative tillage methods were greater than that under T.2. Compared with T, the average LAI, LAD and CAP could be improved under different conservative methods. Form tillering to vax-ripe stage, the average LAI under NTS, NT, NTP, TSand TP improved by33.85%, 13.85%, 46.15%, 15.38%and 20.00% respectively, and the average LAD under them improved by 33.33%,14.29%, 44.44%,14.29%and19.05% respectively. The average CAP of NTS, NT, NTP,TP improved by 24.04%,14.08%, 11.27%and 13.68% respectively except TS form tillering.to milking. The growth stages in which the different tillage methods had the greatest effect on LAI, LAD and CAP were vax-ripe stage, filling to milking, tillering respectively.The relationship between the LAD and grain yield was very intimate, and the LAD in every growth stage was significantly or very significantly correlated to the yield, and the LAI in jointing, booting, filling, milking and vax-ripe stage was very significantly correlated to the yield, The CAP in booting and Pn in flowering were significantly and very significantly correlated to the yield respectively.3. Compared with T, the conservative tillage methods were good for the dry matter accumulation.The average dry matter accumulation under NTS, NT NTP, TS and TP improved by 22.97%, 1.64%,20.47%, 5.92% and 7.06% on the growth stage, the dry matter accumulation under the different tillage methods was very different in every stage,and the growth stage in which the different tillage methods had the greatest effect on dry matter accumulation was tillering.Aftering heading stage,the dry matter transferred into spikes uder NTP was greater than that under other treatments,and the conversion rateunder NTP better than that under other treatments; the ability of allocation and transportation of wheat grain under TS was better than that under other treatments.4. Enforcing conservatively tilling could improved the grain yield and WUE. Compared with T, the yield under the NTS, NT ,NTP,TSand TP improved by 68.10%,12.82%,64.98%,18.66%and30.33% respectively;and the WUE improved by 68.75%,23.96%,66.67%,21.88%and55.21% respectively,and the difference was significant.Among the three basic components of the grain yield, the1000-grain weight and spike number per unit area had no great difference, but grain number per spike had great difference among the different tillage methods. Meanwhile, the grain yield had significant positive correlation to grain number per spike(R=0.96**), and it was not correlated to the1000-grain weight and spike number per unit area.
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