| It was very important to model water and heat transfer in SPAC under furrow irrigation for understanding the quantitative relationships between energy transmission and transition of SPAC, and elucidating the water-saving mechanism and characters of energy transmission of alternative furrow irrigation (AFI). Based on the current situation of water and heat transfer simulation of SPAC under furrow irrigation, the light and temperature distribution on soil surface and the relationships between soil surface resistance, canopy resistance, aerodynamic resistance and environmental factors were analyzed with observations of the light and temperature distribution, soil water and heat transfer parameters, crop root distribution and crop physical indices of maize under AFI and convention furrow irrigation (CFI), and various resistance models were also developed; furthermore, the model of light and temperature distribution on soil surface, two-dimensional model of soil evaporation and root water uptake, and soil water and heat transfer model was developed; the mechanism of soil evaporation, the response mechanism of root morphology to soil moisture and the characters of soil water and heat transfer under AFI and CFI was revealed; the 2-D water and heat transfer model of SPAC under furrow irrigation was developed with the mutual feedback relationships, achieving the dynamic simulation of water and heat variation of SPAC under furrow irrigation. Results were as follows:(1) Total amount of solar radiation on soil surface with West-East row was greater than that with North-South row. For spring maize under AFI with the identical row orientation, solar radiation quantities on non-irrigated zone was greater than that on irrigated zone, therefore, solar radiation quantities on soil surface under AFI was greater than that under CFI. Soil surface temperature variation curve was similar to solar radiation variation trend. Soil surface temperature with West-East row was greater than that with North-South row. For maize with the identical row orientation, soil surface temperature of AFI was greater than that of CFI, the maximum temperature difference and the minimum difference was 4.23℃and 0.06℃, respectively.The model of global radiation transfer on soil surface and soil temperature distribution was developed based on the geometrical relationships between soil surface structures and the incident angle of solar radiation. Variations of solar radiation and soil surface temperature under furrow irrigation were well simulated with the model, and the fitting degree was greater than 0.84.(2) The 2-D model of soil evaporation and crop transpiration under furrow irrigation was developed with the improved S-W model based on dividing soil evaporation zone to wet and non-wet zones under AFI. Soil surface resistance model of dry and wet region under AFI was developed with the Camillo (1986), and Anadranistakis et al (2000) model. The response function of stomatal resistance to water stress under deficient water supply was expressed as the temperature difference in the interior of canopy. Based on the Jarvis (1976) model, canopy resistance model was developed under adequate and deficit water supply; the undermined parameters of the model were calculated with the least square method, then the optimal solution was determined. The simulated values of soil evaporation were similar to the measured values. The relative deviation (MAE), root-mean-square deviation (RMSE) and fitting degree (dl) between the simulated and measured values under AFI was 0.11, 0.33 and 0.87, respectively; the values of MAE, RMSE and dl under CFI were 0.09, 0.31 and 0.90, respectively. Crop transpiration was underestimated with the model. The simulated transpiration under AFI was 0.88 times of the measured values, and the simulated values under CFI were 0.85 times of the measured values.(3) Under AFI, root diameter, root volume density, root tip number, and surface area present the response mechanism to soil water and heat environment. Root growth rate of root zone with water deficit was increased significantly after re-watering, the root death rate decreased, and the'compensational effects'present. Values of root tip number and surface area of fine root under AFI was significantly greater than that under CFI; root depth under AFI was greater than that under CFI, which was favorable to root water uptake.Root length density (RLD) decreased exponentially with depth in lateral and vertical profile. RLD of AFI was not symmetrical distributed with ridge before jointing; RLD was symmetrical distributed with ridge after tasseling. RLD under CFI was symmetrical distributed with ridge. The two-dimensional distribution model of RLD was developed, the simulated values of RLD at different sites under AFI and CFI were similar to the measured values, coefficient of determination were higher than 0.80. The 2-D model of root water uptake under water stress condition was developed with the dynamic distribution of RLD and the Feddes model (Feddes et al., 1978).(4) The simulation errors caused by complex boundary and homogeneous soil were decreased with the division of the simulated domain using the finite element method, and the simulation precision increased using the Galerkin method. Soil water and heat transfer in time and space under AFI and CFI was nicely simulated using the finite element method; the simulated values had a significant correlation with measured values, the simulated values were 0.96 times of the measured values. The simulated values of soil temperature were similar to the measured values, the simulated values were 0.98 times of the measured values.Main innovative points of this paper:①The model of global radiation transfer on soil surface and soil temperature distribution was developed based on the geometric optics, and taking into account of overshadow zone and sunshine zone and soil moist pattern. The light and temperature distribution on different sites of soil surface was well simulated with the model.②The calculation method of surface resistance under AFI and CFI for sandy loam soil at Xinxiang was determined. For the developed model of canopy resistance, the response function of stomatal resistance to water stress under deficient water supply was expressed as the temperature difference in the interior of canopy, which could be easily and simply measured, being superior to express as soil moisture; values of daily variation of canopy resistance could be calculated with themethod, which was feasible and practical.③The S-W model was improved with the complex boundary conditions of furrow irrigation, the homogeneity of soil moisture and variation of microclimate on soil surface, then the 2-D model of soil evaporation and crop transpiration under furrow irrigation was developed, and the values of MAE, RMSE between the simulated and measured values was less than 1, and di greater than 0.87.④The response mechanism of the live and dead roots morphology to soil water condition under furrow irrigation was analyzed, and the 2-D model of root length density distribution, which taking account of the space distribution of root system, and variation of depth of root spread and penetration with time, has high simulation precision and dynamic characters. |
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