Assessing the performance of different irrigation systems on winter wheat under limited water supply

The rapid decline of groundwater table is threatening sustainable irrigation agricultural development in the North China Plain (NCP). Optimized irrigation scheduling and water-saving irrigation technologies need to be developed to reduce irrigation water use and maintain the grain production potential for the region. This study was conducted at Luancheng experimental station in the NCP during 2012-2015 to evaluate the effects of different irrigation methods (basin irrigation, BI; tube-sprinkler irrigation, SI; pillow irrigation, PI and drip irrigation, DI) with various irrigation amount/frequency on yield, economic returns and water use efficiency (WUE) of winter wheat. Under the same limited irrigation amount (90 mm/season), two irrigation applications (45 mm/application) conducted using DI significantly increased the yield and WUE as compared with the BI using one single application. Increasing the seasonal irrigation amount to 160 mm, the increase in the application frequency by reducing the irrigation amount per application didn't significantly affect the yield using either PI or SI. Results showed that soil water depletion (SWD) contributed 40-60% of the seasonal evapotranspiration (ET) under limited water supply. The smaller root length density (RLD) in deep layers of the soil restricted the soil water uptake by the crop. Therefore, increasing irrigation frequency would maintain the top soil layers with higher soil water contents where RLD was greater that improved crop water use and yield under limited water supply. However, when irrigation water was plentiful, micro-irrigation methods did not increase yields. Due to the high cost in installation of the three micro-irrigation systems, their net income was reduced by 30% as compared with the BI method. The economic water productivity ratio (EWPR) was only 3-4 for the three micro-irrigation systems, much less than the basin irrigation method, which had an average value of 16. Currently, the basin irrigation method is more economic for growing winter wheat in the NCP.