| Field experiment was carried out at Wuwei experiment station of Gansu AgriculturalUniversity in2009to2011to study the effects of different multiple cropping on water usecharacteristics. Correlation analysis was also conducted in terms of factors impacting wateruse characteristics. Main results are as follows:1. Among six different multiple cropping in terms of land resources utilization,multiple cropping index of SW-R and SR-P was200%, multiple cropping index ofSW'WR-P and SW'WW-S was150%, multiple cropping index of M-M/Pea-WW andM-M/SW-WR was100%. The output value of SW'WW-S was54995.08yuan/hm~2, thehighest value among six cropping treatments. However, in the present study, output valueof scallion was26097.2yuan/hm~2, significantly higher than that of rape, which was4349.88yuan/hm~2and5647.18yuan/hm~2. This demonstrated that cropping system withhigh cropping index may not always have high output value. Yield of winter wheat inSW'WW-S was6083.3kg/hm~2, this was significantly lower than that of spring wheat inSW'WW-S, SW-R and SW'WW-S, which was6518.8kg/hm~2、7236.8kg/hm~2and7052.1kg/hm~2, respectively. Light use efficiency of M-M/Pea-WW was0.76%,65%higherthan that of SW-R (0.46%). Heat use efficiency of SW'WW-S was4.39kg/hm~2℃-1,54%higher than that of SW-R (2.85kg/hm~2℃-1). This demonstrated that there existed thepossibility to optimizing light and heat use efficiency under different cropping systems inHexi oasis irrigated areas.2. Water use efficiency of SW'WW-S was18.24kg/hm~2mm, the highest valueamong six cropping treatments. Also, water use profitability of SW'WW-S was4.58yuan/m~3, this was due to the long coverage of vegetation and the straw mulching preventingthe soil evaporation from soil surface. Winter wheat and winter rape can protect the surfacesoil from sand storm, the sowing date of winter wheat and winter rape was in the rain richseason of autumn, this makes them have a good use of natural rainfall and reduce thepressure of water use, increase ecological water use. The long vegetation coverage ofwinter wheat and winter rape can prevent the soil evaporation from soil surface, andincrease water storage than other crops. Although the water use of crops in winter wasrelatively low, but water storage was also reduced by soil evaporation and water leaching.3. Economy drives the development of local agriculture, and all agricultural production activity was a matter of economy, light, heat, and water is the prerequisite torealize multiple cropping, this reflects the feasibility of a cropping system. From theeconomic benefits we can see, net profit of SW'WW-S was39056.47yuan/hm2, output toinput was3.45and labor productivity was98.21yuan per man. Labor amounts of SR-P was680, the productivity was the lowest of59.09yuan per person.4. Differences in soil water content were significant, among them, soil layers of0-30cm was the greatest variations because of precipitation, irrigation, and crop types. Whilesoil layers of30-50cm was the water pool for crop growth, these layers were mainlyinfluence by crop water absorption and the vertical distribution of dynamics of soil water.Soil layers of50-110cm was the major regulator of deep soil moisture supply andaccumulation of smaller changes in soil moisture, mainly affected by the impact of leakage,water is relatively stable layer. Soil moisture by rainfall in one degree how much influencechanged significantly. A small amount of rain can only change the soil moisture content ofthe soil surface soil layer (0-20cm), heavy rainfall and irrigation can change the depth ofthe moisture content of the soil at different levels, even if a large number of rainfall orirrigation on soil deep (80-110cm) affect not significantly. Irrigation water redistributionafter the beginning of irrigation infiltration based process, a few days later to evaporativewater loss, soil water redistribution process change.5. Water use efficiency and yield was significant positive correlation at the P <0.01level, the evaporation of water consumption and average daily between crops wassignificant positive correlation at the P <0.05. Soil temperature and water use efficiencywas negatively slightly correlated, visible at a certain temperature, appropriate to reduce thesoil temperature can improve the efficiency of water use; water consumption andevaporation accounts for the proportion of water consumption and was negatively weakcorrelated, rainfall can not control, so reducing irrigation can be reduced waterconsumption leading to increased evaporation accounted for water consumption; water useefficiency and water consumption was negatively weak correlated in Hexi oasis irrigationareas, on the basis of the level of local irrigation can be appropriate to reduce the amount ofirrigation to improve water use efficiency. |
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