Water-saving irrigation modes based on water supply and demand of winter wheat and summer maize

With the industry and agriculture development, water shortage is more and more serious. Water-saving irrigation plays an important role in meeting water resources shortage problems. Water-saving agriculture and improvement of irrigation water use efficiency are developing directions of agriculture. It is important to formulate reasonable crop irrigation system based on the crops water requirement and supply for water-saving irrigation and water resources planning. In this study, soil water content and leakage, water requirement of winter wheat and summer maize rotation system in Qingdao were investigated through simulating field water movement with Hydrus-1D model based on the long term field experiment. According to the water supply and requirement of two crops, suitable irrigation amount and time were discussed. The results showed that the Nash-Suttcliff simulation coefficients Ens of measured and simulated soil water content in 20 cm, 40 cm, 60 cm, 100 cm and 160 cm depths were 0.652, 0.857, 0.852, 0.887 and 0.903 respectively, meaning the model worked well. Human influence resulted in relative worse simulation result in surface soil water content. Under conventional irrigation management with 520 mm irrigation, soil water leakage to 1.6 m depth was 189 mm, about 22.3% of the total amount of irrigation and precipitation. The soil water leakage was serious under conventional irrigation mode, and positively correlated with precipitation and irrigation. The results showed that rainfall during winter wheat growing season was only 61.6 mm, 24.5% of evaportanspiration. There was 300 mm water shortage during winter wheat growing season in the study year. During summer maize growing season, rainfall got up to 93.1% of water requirement of maize. However, complementary irrigation was needed at seeding to seedling and later growth stages due to uneven season distribution of rainfall. The improved irrigation scheme was established based on water supply and demand of summer maize and winter wheat. The irrigation amounts were 50.0 mm and 320.0 mm for summer maize and winter wheat, respectively, 100 mm less than that under conventional irrigation. Water-saving irrigation modes based on the relationship of water supply and demand greatly improved the utilization efficiency of irrigation, and decreased water leakage amount.