| The experiment was conducted in agronomy experimental station of Shandong Agricultural University during 2006 to 2008.The objective of this paper was to investigate the effect and value in production of population distribution on water utilization in winter wheat and summer soybean farmland. Under the conditions of the same density, there were several population distribution patterns by adjusting the row spacing and plant spacing. The summer soybean experiment were made up of 5 distribution patterns with the same plant population density (3.09×105plant·hm-2), and the row spacing (cm)×plant spacing(cm) were 18cm×18cm (A), 27cm×12cm (B), 36cm×9cm (C), 45cm×7.2cm (D), 54cm×6cm (E) respectively. The winter wheat experiment consists of 4 distribution patterns and 4 irrigation schedules with the same plant population density (2.04×106plant·hm-2). Row spacing(cm)×plant spacing(cm) was 7cm×7cm (A), 14cm×3.5cm (B), 24.5cm×2cm (C), and 49cm×1cm (D) respectively. The four irrigation schedules were no-irrigation, irrigations at jointing stage, jointing and heading stages, jointing, heading and filling stages (the amount of irrigation 0.60 m3 every time). These results indicated that population distribution could affect the crop yield and water use efficiency (WUE), improve the dynamics of population developmentally, characteristics of physiological and ecological and water consumption rules effectively. The results were as follows:1. Effects of crop distribution patterns on population develop dynamicsThe leaf area index (LAI) and total dry matter accumulation of A and B treatments were significantly higher than that of other treatments in summer soybean. The pod accumulation of A and B treatment were higher than that of E treatment by 4.73% and 3.88% respectively.In winter wheat experiment, the population numbers of A and B increased quickly at early growing stage, followed by large population with declined rapidly at middle stage, and much more spike numbers at maturity stage, while C and D treatment showed the opposite trends. The LAI and dry matter accumulation declined gradually with the increase in crop spacing, and these of B treatment were 43.8% and 39.8%significantly higher than those of D treatment. Irrigations had an impact on population develop dynamics, but not as good as crop distribution patterns. The number of tiller, LAI, and total dry matter accumulation raised with the increase of irrigation amount2. Effects of population distribution on farmland microclimateThe photosynthetically active radiation (PAR) transmittance ratio raised and PAR capture ratio declined gradually with the increase in crop spacing; Irrigation not only increased the crop RUE significantly, but also had an interaction with population distribution. Compared with other treatments, treatment A and B could significantly reduce the turbulent heat flux and soil heat flux, increase latent heat flux; Irrigation could further improve the farmland microclimate conditions near the ground, reduce air and soil temperature, increase air relative humidity in plants. The air temperature, humidity above ground and soil temperature of 5cm were positively correlated (R=0.978*, 0.908*,0.998**)with turbulent heat flux, latent heat flux and soil heat flux respectively.3. Effects of population distribution on leaf physiological characteristicsThis study indicated that populations with relatively uniform distribution would improve leaf relative water content(RWC), water potential(Ψw), and osmotic potential(Ψs), enhance photosynthetic rate(Pn) and fluorescence in flag leaves of winter wheat, consequently maintain well leaf water characters and physiological functions. Irrigations had a significant effect on leaf physiological characteristics. RWC,Ψw,Ψs, Pn and fluorescence raised with the increase of irrigation amount;4. Effects of crop population distribution and irrigation on the law of water consumptionThe soil moisture content was no significant differences among all treatments in summer soybean population. The field evapotranspiration of A treatment was significantly lower than that of other treatments, and there were no significant differences among others. The WUE of summer soybean population declined gradually with the increase in crop row spacing, and A, B treatment were 21.9% and 22.5% significantly higher than that of E treatment respectively.The soil evaporation intensity increased as the row spacing widened and irrigation amount raised in winter wheat population. Compared with other treatments, A and B treatment could increase the soil moisture content in 0~30cm, but reduce the deep soil moisture content below 30cm. After jointing stage, the phase water consumption amount and intensity of A and B were significantly higher than that of other treatments, thus the evapotranspiration was increased. Soil moisture varieties of A and B were much higher than C and D treatment, which was the main reason why A and B could significantly raise evapotranspiration of winter wheat farmland.The order of WUE among winter wheat population distributions was B>A>C>D, B treatment was 11.6% higher than that of D treatment.The study also indicated that irrigation could increase the soil moisture content and total evapotranspiration, reduce WUE in winter wheat. The population distribution and irrigation not only affected the water use efficiency respectively, but also had an interaction with each other.5. Relationships of population distribution, yield, WUE and RUEThe study found that the yield of B treatment in summer soybean and winter wheat population were both highest, followed by A and C treatment, D or E treatment was the lowest. So the yield decreased gradually with the row spacing widened. The direct reason of yield declined was that the productive pod and seed numbers reduced in summer soybean or spike numbers significantly decreased in winter wheat. The WUE were positively correlated with yield in summer soybean and winter whea(tR=0.997**, 0.995**); Thereby, the B treatment was the best distribution pattern in summer soybean population.The yield and RUE of winter wheat gradually raised, but WUE significantly declined at the same time, with the row spacing increased; Under the condition of irrigation at jointing and heading stages, the WUE and RUE of all treatments were efficient at the same time. In conclusion, the B treatment under the condition of irrigated at jointing and heading stages was the optimal compounding between water and radiation use efficiency.
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