Abstract
To solve the problems of yield reduction and low water-use efficiency (WUE) of winter wheat (Triticum aestivum L.) caused by winter and spring drought, a 2-year field experiment (2017-2019) was performed under movable shelter conditions with the large- and multispike cultivars Shannong 23 and 29, respectively, to explore the optimal supplemental irrigation regime. Three wetting layers were used for irrigation at the jointing stage: 0-10 cm (T2), 0-20 cm (T3) and 0-30 cm (T4). No irrigation at the jointing stage (T1) served as the control. Within a given cultivar, the soil water content in the 0-80 cm soil layers increased after irrigation, and the rate of tiller mortality decreased with increasing depth of the wetting layer used for irrigation at jointing. No significant differences were found between the T3 and T4 treatments in the photosynthetic rate (Pn) of the apical leaf of the main stem (O), the first primary tiller (I) and the fourth tiller (IV) after jointing. However, compared with the T3 treatment, the T4 treatment had a significantly higher transpiration rate (Tr) and lower instantaneous water-use efficiency (WUEleaf) of the apical leaf of the O and tillers I and IV. This eventually led to a decreasing WUE, although there was no significant change in the spike number or grain yield. These results indicated that moderate irrigation at jointing can effectively reduce the tiller mortality, improve the leaf Pn of the tillers, and increase the spike number and grain yield. However, excessive irrigation can significantly increase the leaf Tr of the tillers, lead to inefficient water consumption and significantly reduce the WUEleaf of the tillers and the WUE. Irrigation at the jointing stage brought the soil water content in the 0-20 cm profile to 100% of field capacity, making it the most suitable supplemental irrigation regime for both the large- and multispike cultivars in the North China Plain.
Highlights
Compared with the T3 treatment, the T4 treatment had a significantly higher transpiration rate (Tr) and lower instantaneous water-use efficiency (WUEleaf) of the apical leaf of the O and tillers I and IV. This eventually led to a decreasing WUE, there was no significant change in the spike number or grain yield. These results indicated that moderate irrigation at jointing can effectively reduce the tiller mortality, improve the leaf photosynthetic rate (Pn) of the tillers, and increase the spike number and grain yield
After irrigation at the jointing stage, the relative water content in the 0–80 cm soil layer under the T2, T3, and T4 treatments increased by 16.2%, 18.3%, and 24.5% in SN23, and by 20.5%, 20.8% and 21.6% in SN29, compared with that under the T1 treatment (Fig 1)
The relative water content in the 80–200 cm soil layer did not vary under different treatments in either cultivar
Summary
In China, winter wheat is sown on 2.45×106 ha and yields 1.34×108 t grain [1], and more than 70% of the wheat yield is produced in the North China Plain [2]. Water is the most important limiting factor for wheat production in this region [3]. The distribution of precipitation is uneven, with 70% of rainfall occurring from June to September, and water stress occurs regularly during the winter wheat growing period [4]. Since the 1960s, winter and spring precipitation have decreased, the frequency of water stress during the winter wheat growing period in North China has increased [5], and drought has caused more than a 60% loss of grain production [6,7]. Irrigation plays a crucial role in achieving high grain yield for wheat. Optimal irrigation regimes at the critical growth stage are imperative for improving WUE while maintaining a stable grain yield
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