Research on crop dynamic irrigation lower limit under limited water supply I — Method

In the case that water resources can not meet the irrigation water requirement, how to Irrigate according to the crop optimization irrigation time, maximize benefit of the limited water supply, is an important problem for agricultural sustainable development. So the concept of dynamic irrigation low limit was put forward. The dynamic irrigation low limit relates with crop growth and development time and water supply. When the water supply is small, the irrigation low limit should be reduced in order to make use of limited water supply in the drier later crop growth stage. On this basis the average soil moisture content of main root zone before irrigation under the optimal irrigation schedule is used as a irrigation low limit. By using statistical analysis method the relationship among irrigation low limit value, the corresponding irrigation time and water supply afterwards (The sum of the available irrigation water and rainfall), was determined. The method changed the traditional way to determine the irrigation lower limit solely based on field experiment and to a certain extent, enrich and improve the theory of farmland irrigation. The irrigation prediction based on dynamic irrigation low limit provides key method to implement optimal irrigation schedule and dynamically correct irrigation plan under of limited irrigation.