| Uneven distribution of water resources in China, rational use of resources has become the focus of national attention. Agriculture is the foundation of the national economy, the food is the foundation of agriculture, drought and water shortage has become a constraining factor in the social and agricultural development, so crop water absorption capacity、water-saving irrigation has become a key study.By using mobile canopy, this paper designed an experiment with five different soil water treatments for summer maize, in which the field capacity was 35-45%(W1)、50%-60%(W2)、 65-75%(W3)、80-90%(W4(CK))、95-105%(W5) respectively, to observe and analyze the variation of physiological characteristics index、root-shoot relationship、water use efficiency of summer maize and to explore the relationship between them and the soil moisture. Using stochastic models to simulate the dynamic changes of soil moisture with effective method and had important theoretical and practical significance of the research of soil moisture prediction. The primary conclusions are as follows:(1) Under different soil moisture treatments, the summer maize diurnal variation of the net photosynthesis(Pn)、transpiration(Tr) showed W4(CK)>W5>W3>W2>W1; Stomatal conductance (Gs) diurnal variation presents unimodal peak time with increasing soil moisture and delayed emergence. During the entire growth period, W1～W3 and W5 made SPAD、leaf area index, leaf water potential, crude ear、ear long、ear volume of summer maize decreased, bald long increased、reduced the number of grains per spike, kernel weight, cob weight, total grain weight decreased, eventually lead to reduced production. W3 treatment had less effect on corn yield than W5, while W1 treatment had greatest effect on summer maize yield. Under silking stage and milky stage of maize, water stress and mild flooding could reduce Pn and Tr, while silking stage of Pn and milky stage of Tr were more sensitive to soil moisture.(2) The less soil water content, the more obvious root -shoot dry biomass, plant height and stem diameter decreased. At the stages of Silking and milky, canopy temperature diurnal variation were the trend of bimodal and unimodal respectively, canopy temperature trends under different treatment canopy for W1>W2>W3>W5>W4(CK). The more severe water stress, maize root-shoot ratio and the maximum growth rate of the shoot of the early appearance, W5 had great impact on the root-shoot dry weight of proportional distribution. By fitting correlation showed: Root dry weight and plant height was significantly binomial correlation (P<0.01), root and shoot dry weight was associated exponentiation (P<0.05).(3)With the enhancement of water stress, water use efficiency (WUE) increased, water-saving capability got stronger, too much water could not conducive to increase of WUE. During different growth period and different water treatments, the WUE was silking stage> milky stage> jointing stage, silking stage for water critical period, W3 had the highest WUE, while W5 could not significantly improve WUE. Correlation analysis showed that:WUE and Pn had a very significant positive correlation, WUE and Tr、Gs had a significant negative correlation, Gs and Tr had a significant positive correlation, when crops affected by drought, mainly reduced Tr to improve WUE. Corn canopy temperature and WUE significantly associated (P<0.05), root-shoot ratio and WUE significantly correlated (P<0.01), soil moisture content and WUE were three four-type relationship, when the canopy temperature、root-shoot ratio can be used as indicators to monitor WUE, then can reflect soil moisture conditions.(4)By using BP neural network to discuss sensitive analysis of meteorological factors on soil moisture sensitivity, three soil moisture training samples and test samples of the simulation accuracy reached more than 0.87、0.97, so the method of soil moisture dynamics simulation by BP neural network can be applied to different soil layers in Nanjing typical farmland, for the forecast of soil moisture, irrigation, soil moisture and provide scientific basis for regulation. |
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