Water-yield function of winter wheat and its application

In North China Plain (the Yellow-Huai-Hai Plain), per capita fresh water is less than 500 m(3) per year, and about 7.7% of the total available water is irrigating 39% of the total farmlands and bringing up about 35% of total population in China. Moreover the ecosystems of this region have sacrificed significantly because the pumping of underground water in the areas is exceeding the recharge rate of aquifers. Many studies claimed that the development of a sustainable water supply for this region is an essential factor of the China's food security and national economy. Agriculture in the North China Plain is very intensive, and winter wheat is a dominant crop that depends highly on irrigation. Great attention has been paid to improve irrigation water management for winter wheat production in this area aiming to increasing water and land productivity. Based on the field experiments at Chahezui Irrigation Experiment Station in Heilonggang, this paper presents the evapotranspiration (ET) of winter wheat and its changing pattern with different water supply, analyses the components of water consumption on-farm level and discusses the major influencing factors over ET of winter wheat. To avoid evident reduction of crop yields or other negative impacts resulting from the change of irrigation practices, the models of water production function (WPF) for winter wheat are carried out, and then, the optimum irrigation regimes for winter wheat in different hydrological years are suggested. These irrigation regimes concern the physiological and ecological water requirements of winter wheat, soil moisture and rainfall, and both irrigation depth and irrigation events may be reduced with surface irrigation. The case study shows that the recommended irrigation practices are feasible and simple for farmers to use.