Planting under plastic-film mulches is widely used in spring maize production in arid-cold regions for water conservation and warming the soil.  To ameliorate the associated issues such as plastic-film residues and additional labor during the “seedling release” in spring maize production, we have developed a plastic-film-side seeding (PSS) technology with the supporting machinery.  In the semi-arid regions of Northwest China, a 7-year trial demonstrated that PSS increased plant number per hectare by 6 547 and maize yield by 1 686 kg ha^–1 compared with the traditional method of seeding under plastic-film mulch (PM).  Two-year experiments were conducted in two semi-arid regions to further understand the effects of PSS on three important aspects of production: (i) the moisture and temperature of soil, (ii) maize development, yield output, and water use efficiency (WUE), and (iii) the revenue and plastic-film residuals in comparison with that of flat planting (CK) and PM.  Continuous monitoring of the soil status demonstrated that, compared with CK, the PSS treatment significantly increased the temperature and moisture of the 0–20 cm soil in the seeding row at the early stage of maize development, and it also promoted grain yield (at 884–1 089 kg ha^–1) and WUE, achieving a similar effect as the PM treatment.  Economically, the labor inputs of PSS were equal to CK, whereas the PM cost an additional 960 CNY ha^–1 in labor for releasing the seedlings from below the film.  Overall, the PSS system increased profits by 5.83% (547 CNY ha^–1 yr^–1) and 8.16% (748 CNY ha^–1 yr^–1) compared with CK and PM, respectively.  Environmentally, PSS achieved a residual film recovery rate of nearly 100% and eliminated 96 to 130 kg ha^–1 of residual plastic-film in PM in 3–5 years of maize production.  Collectively, these results show that PSS is an eco-friendly technique for improving yield stability and incomes for the sustainable production of maize in semi-arid regions.

To improve efficiency in the use of water resources in water-limited environments such as the North China Plain (NCP), where winter wheat is a major and groundwater-consuming crop, the application of water-saving irrigation strategies must be considered as a method for the sustainable development of water resources.  The initial objective of this study was to evaluate and validate the ability of the CERES-Wheat model simulation to predict the winter wheat grain yield, biomass yield and water use efficiency (WUE) responses to different irrigation management methods in the NCP.  The results from evaluation and validation analyses were compared to observed data from 8 field experiments, and the results indicated that the model can accurately predict these parameters.  The modified CERES-Wheat model was then used to simulate the development and growth of winter wheat under different irrigation treatments ranging from rainfed to four irrigation applications (full irrigation) using historical weather data from crop seasons over 33 years (1981–2014).  The data were classified into three types according to seasonal precipitation: <100 mm, 100–140 mm, and >140 mm.  Our results showed that the grain and biomass yield, harvest index (HI) and WUE responses to irrigation management were influenced by precipitation among years, whereby yield increased with higher precipitation.  Scenario simulation analysis also showed that two irrigation applications of 75 mm each at the jointing stage and anthesis stage (T3) resulted in the highest grain yield and WUE among the irrigation treatments.  Meanwhile, productivity in this treatment remained stable through different precipitation levels among years.  One irrigation at the jointing stage (T1) improved grain yield compared to the rainfed treatment and resulted in yield values near those of T3, especially when precipitation was higher.  These results indicate that T3 is the most suitable irrigation strategy under variable precipitation regimes for stable yield of winter wheat with maximum water savings in the NCP.  The application of one irrigation at the jointing stage may also serve as an alternative irrigation strategy for further reducing irrigation for sustainable water resources management in this area.

    To understand the contribution of ear photosynthesis to grain yield and its response to water supply in the improvement of winter wheat, 15 cultivars released from 1980 to 2012 in North China Plain (NCP) were planted under rainfed and irrigated conditions from 2011 to 2013, and the ear photosynthesis was tested by ear shading. During the past 30 years, grain yield significantly increased, the flag leaf area slightly increased under irrigated condition but decreased significantly under rainfed condition, the ratio of grain weight:leaf area significantly increased, and the contribution of ear photosynthesis to grain yield changed from 33.6 to 64.5% and from 32.2 to 57.2% under rainfed and irrigated conditions, respectively. Grain yield, yield components, and ratio of grain weight:leaf area were positively related with contribution of ear photosynthesis. The increase in grain yield in winter wheat was related with improvement in ear photosynthesis contribution in NCP, especially under rainfed condition.

The photosynthetic characteristics of flag leaf and the accumulation and remobilization of pre-anthesis dry mass (DM) and nitrogen (N) in vegetable organs in nine wheat cultivars under different source-sink manipulation treatments including defoliation (DF), spike shading (SS) and half spikelets removal (SR) were investigated. Results showed that the SS treatment increased the photosynthetic rate (Pn) of flag leaf in source limited cultivar, but had no significant effect on sink limited cultivar. The SR treatment decreased the Pn of flag leaf. Grain DM accumulation was limited by source in some cultivars, in other cultivars, it was limited by sink. Grain N accumulation was mainly limited by source supply. The contribution of pre-anthesis dry mass to grain yield from high to low was stem, leaf and chaff, while the contribution of pre-anthesis N to grain N from high to low was leaf, stem and chaff. Cultivars S7221 and TA9818 can increase the contribution of remobilization of DM and N to grain at the maximum ratio under reducing source treatments, which may be the major reason for these cultivars having lower decrease in grain yield and N content under reducing source treatments.