Analysis of field water consumption, its pattern, impact and driving factors

Agricultural water use accounts for about 70% of total water consumption in the North China Plain (NCP). So, the researches on field water consumption and its pattern, impact and driving factors critical for developing agricultural water-saving practices and also learning water transfer mechanisms in soil-plant-atmosphere continum (SPAC) are very important. This paper reviewed the proceedings in field water cycle and water-saving research in the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences since its establishment. Long-term site-specific experiments on irrigation schemes since 1985, straw mulching schemes since 1986, tillage schemes since 2002, large weighing lysimeter data streams since 1995, and other agro-experiments have been conducted at the station. Water balance methods and large weighting lysimeter data were used to estimate evapotranspiration (ET) in the station. Soil evaporation (E) was measured using the micro-lysimeter method. The results showed that water consumption during winter wheat and summer maize cropping periods was similar, averaging 430 mm per cropping season. The trend in water consumption increased with increasing irrigation of winter wheat, which had increased on the average from 283 to 493 mm. The coefficient of variation in ET was negatively correlated with irrigation, and was mainly driven by precipitation difference. The ratio of E to ET for winter wheat and summer maize was 1/3, and also similar for the tow crops. This implied that limiting E was a critical water-saving factor in the region. Field experiments at Luancheng station in recent 20 years showed that straw mulching significantly reduced E, to somewhere in the neighborhood of 40~50 mm. Wheat and maize straw mulching reduced E by 58.0% and 40.4% in summer maize and winter wheat fields, respectively. Despite the fact that differences in E existed for different field tillage practices,zero-tillage, as compared with traditional tillage, significantly reduced E. The irrigation, tillage and planning schemes as well as canopy characteristics affected crop water consumption and agricultural water-saving in the region. The above findings laid the basis for theoretical and technical developments of agricultural water-saving practices in NCP.