| Field experiment and research in LongDong dry land area between year 1998- 1999 showed that: 1. The timeline change of soil moisture in winter wheat/corn intercropping For Winter wheat of wheat/corn intercropping in 0-30cm, 3 0-60cm, 60-90cm. and 0?0cm depth in Soil layer throughout whole growth stage, the highest soil water content(SWC) was in presowing stage (i.e. 17.55%, 15.18%, 15.40%, 16.04% respectively), while a continuous decreasing of that was seen after sowing before a slight restoration in flowering to filling sta2 except 0-30cm depth. Till maturity SWC was about 47% of that of presowing (8.28%, 6.4 1%, 7.45%, 7.37% respectively), and a tendency was found that SWC in average 90cm depth is similar as that in 60-90cm depth. For corn the change of SWO in each layer throughout the whole growth stage showed a consistency with a ingle Peak?curve in small horn stage (19.03%, 17.19%, 14.98%, 17.05% respectively), and reached their lowest point in maturity stage, which was about 33% of that ofpresowing, i.e. 4.64%, 4.14%, 7.06%, 5.28% respectively. Analysis and comparation indicated that the highest contribution to soil water by limited irrigation in all growth stages for wheat is in jointing stage(JS) and then heading stage (HS) , and flowering stage (FS) follows it, while in filling stage(FLS) see its lowest SWC. For corn the sequence is large horn stasre(LHS), heading and flowering stage(HFS), silking stage(SS), and FS, that is to say, the earlier irrigation, the more contribution to soil moisture. 2. The vertical change of soil moisture in winter wheat/corn intercropping. Whether irrigated or not, SWC (mm) of winter wheat since HS and of corn since Six-leaf Stage(SLS) in 30-60cm depth become gradually lower than that of in 0-30cm and 60-90cm depth and SWC in these three diffent depths in intercropping treatments also become lower than that of in sole winter wheat and corn respectively since JS of winter wheat and SLS of corn. Analysis and comparation indicated that percentage of SWC in different depth since the 2th growth stage after irrigation of wheat and corn began to keep on a stable level, but the percentage varied with the change of irrigation time. 2. With the aid of regression analysis simulation models were developed in each winter wheat/corn treatment through all growth stages, which is expressed as equation Wc/(l+ea.bt) for wheat and Waebt2 between W(SWC, %) and t (days after sowing). 45 4. As far as the compound intercropping canopy is concerned, relative productivity under limited irrigation conditions was much higher than that of no irrigation treatment. Furthermore, significant effects of yield increasing in irrigation treatments were found by a 13.0-40.8 percent more in Economic Yields (Ye) than that of no irrigation treatment, i.e. the highest Ye under irrigation conditions was 12787.0 kg/bin2, while the lowest Ye was 10258.? Kg/bIn2. For wheat/corn canopy the most appropriate sequence of growth stages regarded as irrigation time by yields increasing was wheat uS and corn HFS (WC3 treatment). wheat FS and corn SS (WC4 treatment), Wheat JS and corn LHS (WC2 treatment), wheat and corn FLS (WC5 treatment). and no irrigation treatment (WC 1). So wheat HS and HFS was considered as the best irrigation time for wheat/corn cc mpound canopy. In the other hand, Water Use Efficiencies (WUE) in all irrigation treatments were higher than that of no irrigation treatment, which was the same consistency as Ye. That is to say, for WUE the sequence from hi...
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