Study On Water Use Efficiency Of Summer Maize Based On Crop Growth Simulation Model In North China

The summer maize is one of the main crop of Northern China. The maize products in Northern China play a significant role in the maize products in China. Although it is rainy season during growth and development of summer maize, the variability of precipitation is great. The drought of different timescales still happens frequently. In addition, the problem that the water of agriculture is insufficient is becoming more and more obvious. because of the expanding irrigation areas and the growing confilicts of using water between agriculture and industry. The relation between the growth of crop and consumption of water resources should be known. Water use efficiency is an important parameter to study the relation between crop and water. It is also an important way to coordinate the conflict between high-yield and water deprivation. In this paper, the foreign crop growth simulation model (WOFOST) was adjusted and the model has been improved in the process that water stress influences the distribution of dry matter of summer maize. This paper gave some methods that described the water use efficiency of maiz based on WOFOST model. And then, the study about spatiotemporal dynamics of water use efficiency of summer maize in North China was carried out by using crop model. The main outcomes in this study are as follows:(1) The growth parameters of WOFOST model was defined by using experiment data, default value and re-estimated parameters. Based on the spatial dynamics of development parameters,the terrain of representative locations and the outcome of climatic regionalization of summer in China, the development parameters were regionalized. According to the soil type map of China, the soil parameters were regionalized. It was proved that the adjusted WOFOST model can be used to simulate the summer maize growth, development and the soil water dynamic after the model tested. It was realized that the WOFOST model was localized and applied.(2) According to field experiment data, the submodel that water stress influences the distribution of dry matter of summer maize was set up. It was proved that the agreement between simulated earweight and measured earweight was better than the one without adding the submeodel, but the simulations about the biomass and the oil water dynamic were not improved obviously.(3) At potential production level the gross assimilation rate of CO2, the transpiration rate and at water limited production level the dry weight of living storage organs, the total above ground production, the transpiration rate, the evaporation rate from soil or from water stored on soil surface were simulated by WOFOST model. The WUE at different levels were defined, which were included blade level, plant population level and yield level.(4) WUE1 was decreased during the development, but the changes were not clear. At DVS=0.6 (shooting period),WUE2 and WUE3 had the same change. At initial stage of maize development WUE3 was accrescent gradually. At the stage that DVS=1.2 (spin) WUE3 was the greatest, after that it began to decrease. WUE4 kept a high level between the stage 1.3 (DVS) and 1.8 (DVS). WUE5 and WUE4 had the same change. The chronic change of water use efficiency were not clear in North China. It can be only found that the water use efficiency was higher in 80s than other chronicle. The chronic changes of water use efficiency at every small region was more clear than whole region of North China, but the changes of every s mall region were different.(5) In North China, water use efficiency of summer maize had a degressive trend from the north to the south. In the 1960s the difference of water use efficiency was obvious between the north and the south. The water use efficiency had some advance at the south of the north china in the 1970s. The water use efficiency continued to increase at north Beijing and the north of Henan in 1980s. However, the water use efficiency was depressing at the central section of the North China in 1990s. The spatial dynamics of WUE was influenced mainly by the total above ground production.