Effects of Water Deficit and Supplemental Irrigation on Winter Wheat Growth, Grain Yield and Quality, Nutrient Uptake, and Residual Mineral Nitrogen in Soil

Abstract

Water deficit (WD) is a primary factor that limits winter wheat (Triticum aestivum L.) production in the Loess Plateau of China, as rainfall during the growing season is usually low and erratic in this region. Supplemental irrigation (SI) in early winter and/or early spring has been widely practiced to mitigate this problem. However, the timing at which WD and SI occur can influence grain yield and quality. A simulation pot experiment was conducted from October 1999 to June 2000 to determine the effects of WD and SI applied at different stages on winter wheat growth, grain yield and quality, nutrient uptake, and residual mineral nitrogen (N) in soil. The results showed that wheat at tillering, stem elongation, and grain‐filling growth stages was more sensitive to WD than at dormant stage. Water deficit at stem elongation or grain‐filling stage not only decreased biomass, but it also appeared to have inhibited the translocation of assimilates from the vegetative plant parts to the heads, especially when WD occurred during grain‐filling stage. Water deficit at dormant stage had no significant effect on biomass production, but it may have hindered the allocation of assimilates to the heads. Water deficit at tillering tended to increase grain harvest index but decreased biomass. Grain yield was significantly decreased (15–91%) by WD at all four growth stages. Translocation of N, phosphorus (P), and potassium (K) also appeared to have been pronouncedly impeded by WD. This inhibitory effect was more apparent at the advanced growth stages of winter wheat. Supplemental irrigation applied at dormant or grain‐filling stage increased grain yield (12% and 35%, respectively). Of the nutrients uptake, only N uptake in grain was increased (21%) when SI occurred at grain‐filling stage. Application of SI at tillering stage significantly decreased grain yield and N and P uptake in the grain, possibly due to decreased biomass and nutrient uptake in the whole plant. Supplemental irrigation at elongation stage increased biomass and N, P, and K uptake in the whole plant, but it appeared to have decreased translocation of assimilates and nutrients to the heads. Supplemental irrigation decreased or had no effect on N, P, and K concentration in grain. The main form of residual mineral N in soil was nitrate‐N, and it was markedly increased when WD was applied at all growth stages or when SI was applied at tillering stage. Supplemental irrigation at elongation or grain‐filling stage significantly decreased residual soil nitrate‐N.

Keywords:

• Grain quality
• grain yield
• residual mineral N
• supplemental irrigation
• water deficit
• winter wheat

Acknowledgments

This work was part of the key project (30230230) and general projects (40201028, 30370843, and 30070429) successively supported by the National Natural Science Foundation of China (NFSC) and of the project (G1999011707) supported by National Key Basic Research Special Funds (NKBRSF). The authors would like to take the opportunity to thank the NFSC and the NKBRSF for their financial support in these projects.