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To clarify the influence of post‐jointing drought on the ear‐bearing and seed‐setting characteristics of the main stem and tillers of winter wheat (Triticum aestivum L.), a pot experiment was conducted with cultivars "Shannong 29" (SN29) and "Heng 0628" (H0628), and five water regimes: mild drought (WR1) and severe drought (WR2) for 0–5 days after jointing, mild drought (WR3) and severe drought (WR4) for 0–10 days after jointing and adequate water supply as a control (CK). The present study focused on primary tillers (appear in the axils of main stem leaves: T1, T2, T3, T4, etc.), as well as on secondary tillers (appear from the bud in the axil of the prophyll: T10 and T20; appear in the axil of the first leaf of the primary tiller T1: T11). The yield components of tillers showed a downward trend with increasing tiller position and drought degree and duration, and the kernels per spike, single kernels weight and grain yield per spike of tillers T2, T3, T10 and T4 decreased more than those of the other tillers. These outcomes may be related to the spike developmental stages at the time of the drought period. Severe drought during the period from when the stamen primordium is first present (Waddington's stage 4) to when the carpel extends around the three sides of the ovule (Waddington's stage 5) significantly decreased the seed set of tillers, but short‐term (5 days) mild drought during this period and even a short‐term severe drought before Waddington's stage 4 had little effect on the seed set of tillers. The ear‐bearing capacity of tillers was determined not only by the spike developmental stage, but also by the gap from the main stem and the competition of nutrition and space between tillers. Although the ear‐bearing rate of tillers T3 and T10 decreased rapidly after the short‐term mild drought, the increase in the ear‐bearing rate of tillers T20 and T11 effectively compensated for the loss of the number of spikes per plant. Therefore, the short‐term mild drought at the jointing stage had no significant effect on the grain yield of the two cultivars. The tillers T2, T3, T10 and T4 were sensitive to soil moisture in the jointing stage and had high plasticity. During this period, if timely irrigation improves soil moisture, it is expected to increase the ear‐bearing rate and seed set of these tillers, thereby increasing grain yield. [ABSTRACT FROM AUTHOR]

Supplemental irrigation (SI) is considered as one of the effective water management practices for improving grain yield and nitrogen utilization efficiency (NU t E) in winter wheat (Triticum aestivum L.). However, whether SI increases grain yield and NU t E by improving the N status in winter wheat is unclear. Based on a two-year field experiment (2017–2018, 2018–2019), we studied the effects of different levels of SI (i.e., no SI (J0), volumetric soil water content at100% field capacity at 20 cm (J20), and volumetric soil water content at 100% field capacity at 40 cm (J40)) and winter wheat cultivars (i.e., large spike-type Shannong23 (SN23) and multi spike-type Shannong29 (SN29)) on grain yield, NU t E and N status in winter wheat of the North China Plain. Our results indicated that, grain yield had a significant positive correlation with the amount of photosynthetic N (PN) at anthesis. With an increase in the N accumulation in shoots at anthesis (NAA), the amount of PN increased first and then remained stable, whereas the amount of reserve N (RN) increased continuously. Compared with SN29, SN23 allocated more N to PN and storage RN and less to structural N (SN) and accumulation RN at anthesis and had higher NU t E. Supplemental irrigation at jointing stage significantly increased the amount of NAA and pre-anthesis N redistributed to grains, and its contribution to grains, while the highest grain yield, NU t E, and water productivity (WP) were reached in J20 and not J40. WP was positively related to the amount of NAA and was also affected by the N nutrition index (NNI) at anthesis. The NNI of winter wheat under J20 treatment is optimal (approximated 1). In J40, with the higher irrigation amount, actual crop evapotranspiration (ET c act), the amounts of NAA and RN, and the NNI at anthesis increased further, but the amounts of PN and grain yield were not affected, which explained the reductions in NU t E and WP. Overall, moderate SI increased winter wheat grain yield and NU t E by improving N nutrition status as indicated by the NNI. And the NNI at anthesis is an important indicator to help manage irrigation and improve grain yield, NU t E, and WP in winter wheat on the North China Plain. [ABSTRACT FROM AUTHOR]