Suitable water deficit mode for winter wheat basing objective of water saving as well as high yield and quality

Abstract: Agricultural water was stress in Haihe River Basin of China, many peasants had given up farming because of irrigation water shortage during the critical period of crop water requirement, if this trend continues, local food security would be affected. Therefore, profound understanding crop's water requirement rules and improving agricultural water use efficiency is very important. Winter wheat is one of the crops that have the largest acreage and high water consumption during the whole growth period, and occupies an important position in the diet of local residents. Therefore, we conducted a water-controlling field experiment to examine the effects of water deficit on the yield and protein formation of winter wheat during the growth and development stages, and meanwhile determined the better water deficit level at each development stage for the objective of water saving as well as high yield and quality. Two water deficit levels were set up during four growth and development stages including green stage, jointing stage, heading and flowering stage, filling and ripening stage. The two water deficit levels were light water deficit (L, soil moisture content was field capacity 55%-60%, soil water suction was 375-448 kPa) and moderate water deficit (M, soil moisture content was field capacity 45%-50%, soil water suction was 586-687 kPa). Moreover, proper soil water treatment during whole stage (CK) was also set up with soil moisture content being of field capacity 65%-70% and soil water suction 256-305 kPa. Our results showed that comparing with the proper soil water treatment (CK), the filling period shorten by 2.72%-15.78% under the deficit treatments. The time for arriving maximum filling speed were advanced with a range of 2.33%-14.58%. All deficit treatments increased the maximum filling speed and the average filling speed except for the treatments of light and moderate water deficit at the filling and ripening stage, and the maximum values were 15.77% and 12.09%, respectively. The basic trend of protein formation showed a "V-shape" curve, which was unchanged by deficit treatments, protein contents and yields various with water deficit treatment. Protein content increased with the aggravation of water deficit at all growth stages except for the green stage. Moderate water deficit at filling and ripening stage featured with the maximum protein content (14.33%), and the light water deficit at jointing stage with the minimum protein content (12.88%). Proper soil water treatment during whole stage (CK) featured with the maximum protein yield (1047.30 kg/hm2), light water deficit at jointing stage featured with the minimum protein yield (802.77 kg/hm2).These results suggested that giving consideration to winter wheat yield and protein yield both, suitable deficit treatments successively were light water deficit at green stage, moderate water deficit at green stage, light water deficit at filling and ripening stage, light water deficit at heading and flowering stage, moderate water deficit at jointing stage, and light water deficit at jointing stage. Our results are important for providing theory and data to the cultivation of winter wheat for water saving as well as high yield and quality.