Characterization Of Evapotranspiration Rules And Their Influencing Factors In Wheat-corn Intercropping Field In Oasis Area

Wheat-corn intercropping is a high-yield culture pattern in northwestern of our country, especially in HEXI oasis irrigation area. Unfortunately, because of the limit of water resource and backward irrigation techniques, the extensions of intercropping methods are facing many resistances. Therefore, the exploitation and development of intercropping techniques characterizing with high efficiency and water-saving are becoming urgent problems. By controlling water supplication and stubble height, the yield, water use efficiency, water consumption, soil evaporation and their impact factors were determined in this study. The main results were as follows:1. Intercropping promoted the efficiency of land utilization for wheat and corn planting; high level of water supplication benefited the yield of intercropping, but harvesting wheat with high stubble left didn't significantly affected it. With low, moderate or high water supplication, wheat-corn intercropping without stubble and that with high stubble had land equivalent ratios (LER) of 1.20～1.25 and 1.19～1.30, respectively, indicating that water supplication and stubble holding did not soundly impacted on LER. Compared to that of moderate and low water supplication, the yields were promoted by employing high water supplication in the same cultivation patterns, e.g. the later one contributed 0.8% and 4.8%,15.9% and 4.7%,15.5% and 9.2%,22.2% and 1.2% higher yields than the former two supplication levels in wheat monoculture, corn monoculture, wheat-corn intercropping without stubble and wheat-corn intercropping with stubble.2. In whole life period, total water consumption, water evaporation, and the value of water evaporation to total water consumption (E/ET) by employing wheat-corn intercropping than wheat monoculture or corn monoculture; Furthermore, within a same culture pattern, the more the water supplied, the more the water consumed; Third, high wheat stubble had different effects on total water consumption depending on the levels of water irrigation. Within the same level of water supplication, e.g., low, moderate and high levels, wheat-corn intercropping without stubble and wheat-corn intercropping with stubble consumed 24.4%～26.3% and 23.4%～25.4% more water than wheat monoculture and corn monoculture, respectively; in the case daily water evaporation, these value were 4.4%～7.1% and 0.8%～2.6% bigger in average, respectively; and for E/ET value, they were 7.8%～9.7% and 2%～2.6% bigger in average, respectively. With high level of water supplication, total water consumption were 11.7%, 8.7%, 10.8% and 9.9% higher than that of modulate supplication and 22.9%, 17.7%, 23.7% and 21.2% higher than that of low supplication within the patterns of wheat monoculture, corn monoculture, wheat-corn intercropping without stubble and wheat-corn intercropping with stubble. 3. Intercropping had a higher efficiency of water utilization than wheat or corn monoculture. It was useful for the promotion of water use efficiency that wheat monoculture, corn monoculture, wheat-corn intercropping with high stubble, under the condition of modulate water supplication, and that of wheat-corn intercropping without stubble combined with low water supplication. The ways of stubble-retaining harvesting did not greatly affect the water use efficiency. Within the same level of water supplication, e.g., low, moderate and high levels, wheat-corn intercropping without stubble and wheat-corn intercropping with high stubble consumed 1.9%～6.6% and 2.4%～13.3% more water than wheat monoculture and corn monoculture, respectively. Compared with low and high water supplication, modulate supplication resulted in 2.8% and 1.9%, 3.6% and 10.2% higher water use efficiency in corn monoculture and wheat-corn intercropping with high stubble, respectively. In addition, wheat monoculture and wheat-corn intercropping without stubble had 5.8% and 17%, 8.1% and 3.9% higher water sue efficiency with low water supplication than with modulate or high water supplication, respectively.4. Under the pattern of intercropping, all the factors of soil evaporation, soil temperature, soil water content, rainfall amount, irrigation amount and water consumption were very significantly correlated with the yield, respectively. And those factors of soil evaporation, soil temperature, rainfall amount, irrigation amount, water consumption and yield were very significantly correlated with the water use efficiency, respectively. Soil water content only weakly positive correlated with water use efficiency.Both soil temperature and soil water content were higher in intercropping than that in monoculture of wheat or corn; soil water content increased as the soil depth increasing; soil water content showed decreasing from wheat belt to interval zone to corn belt. Within the same level of water supplication of low, moderate and high levels, compared those of wheat-corn intercropping without stubble and wheat-corn intercropping with high stubble to those of wheat monoculture and corn monoculture, soil temperatures were 0.4%～1% and 0.5%～3.7% higher, respectively; Soil water content of 0～150cm depth were 2.9%～4.1% and 2.4%～5.1% higher in average, respectively. After harvesting of wheat, wheat belt had 9.5% more soil content than interval zone and 11.1% more than corn belt.