Study On Water Use Efficiency For Apple Grown Under Controlled Root-divided Alternative Irrigation

China is one of the 13 water-poor countries in the world.Its total freshwater resources is only 8% of the world, and per capita possession of water resources is no more than 1/4 of that in the world.Water deficit has become an important factor which constrains the development of agricultural economy and rural society.The cultivation area and production of apple are on the top in the world apple production. But apple production is mainly in the arid and semi-arid areas, drought is one of the main factors affecting apple quality and yield. Therefore, studying water-saving irrigation technology for apple orchards in arid areas is the key to sustainable development. So studying the effects of partial rootzone alternative irrigation on physiology and water-saving efficiency in apple, and analyzing feasible irrigation pattern, have important theory meaning and practical value for improving WUE in orchard irrigation.Using three-year potted apple trees("Royal Gala") with their roots partitioned, an experiment consisting of four treatments of root irrigation, irrigating one fourth of the root- zone,two fourths of the rootzone,three fourths of the rootzone and the whole rootzone, are conducted to study the effects of controlled root-divided alternative irrigation on LWP, Rs, Pn, Tr, Gs, shoot, leaf area, trunk, biomass and WUE under three different levels of irrigation(50%,75%,100%).The major results can be summarized as below:1. LWP changed dialy in a"V"font curve. Under the same amount of irrigation, dialy change of LWP wasn't notably different between one fourth and two fourths of the rootzone irrigation, neither between three fourths of the rootzone and the whole rootzone irrigation.The LWP of one fourth of the rootzone irrigation was at the lowest value in a day, while was at the biggest value in the whole rootzone irrigation.In one fourth of the rootzone irrigation, LWP wasn't notably different among three amounts of irrigation in a day, but it was on the contrary to the whole rootzone irrigation.In two fourths and three fourths of the rootzone irrigation, LWP was notably different betweent 50% and 100% amount of irrigation in a day.2. During the whole growing stage, the LWP at dawn was high in early period and to descend in later period, which was on the contrary to the LWP at noon.Under the same amount of irrigation, LWP was notably different between one fourth of the rootzone and the whole rootzone irrigation treatment, but wasn't notably different between two fourths and three fourths of the rootzone irrigation treatment.The LWP in one fourth of the rootzone irrigation treatment was at the lowest value all the time, while was at the biggest value in the whole rootzone irrigation.Under the same treatment, the LWP at dawn wasn't notably different among three amounts of irrigation, but The LWP at noon under 50% amount of irrigation was obviously lower than that under 100% amount of irrigation.3. Rs changed dialy in a"W"font curve.Under the same amount of irrigation and different rootzone irrigation treatments, Rs was significantly different in the whole day.The bigger the non-irrigation size became, the bigger Rs became. Under the same rootzone irrigation treatment and three amounts of irrigation, Rs was also notably different in a day.The sequence of Rs under three amounts of irrigation was:50% >75% >100%.4. During the whole growing stage, Rs increased with the LWP decreasing.Under the same amount of irrigation and different rootzone irrigation treatments, Rs was notably different. The sequence of the Rs was one fourth of the rootzone, two fourths of the rootzone, three fourths of the rootzone and the whole rootzone irrigation. Under the same rootzone irrigation treatment, the larger amount of irrigation was, the littler Rs was.5. In different growth stages, Pn,Tr and Gs of leaves decreased when only partial rootzone was irrigated.Because Tr decreased more than Pn, the WUE increased.Pn,Tr and Gs which were affected by different amount of irrigation were insignificantly different.6. The growth of shoots was inhibited when only partial rootzone was irrigated.In addition, the bigger the non-irrigation size and smaller amount of irrigation became, the stronger the inhibition became.7. The growth of leaves was inhibited when only partial rootzone was irrigated.Under the same treatment, the larger amount of irrigation was, the larger leaf area was.8. Under 50% and 75% amount of irrigation, the growth of basal trunk was inhibited when only partial rootzone was irrigated, and it was notably affected by different amount of irrigation under three fourths of the rootzone and the whole rootzone irrigation treatment.9. Partial rootzone alternative irrigation reduced the total biomass and the growth volume of roots, but the root/shoot ratio was increased.The sequence of the root/shoot radio was:two fourths of the rootzone > one fourth of the rootzone > three fourths of the rootzone > the whole rootzone.The root/shoot ratio under 75% amount of irrigation was the biggest in one fourth of the rootzone,two fourths of the rootzone and three fourths of the rootzone irrigation treatment.10. With little sacrificing the accumulation of biomass, the WUE under two fourths of the rootzone and 75% amount of irrigation treatment was higher than that of the whole rootzone, but water consumption reduced by 50.61% and the biomass decreased only by 24.75%, and the water-saving profit was significant.