Soil management practices affect rhizosphere microorganisms and enzyme activities, which in turn influence soil ecosystem processes. The objective of this study was to explore the effects of different nitrogen application rates on wheat (Triticum aestivum L.) rhizosphere soil microorganisms and enzyme activities, and their temporal variations in relation to soil fertility under supplemental irrigation conditions in a fluvo-aquic region. For this, we established a split-plot experiment for two consecutive years (2014–2015 and 2015–2016) in the field with three levels of soil moisture: water deficit to no irrigation (W1), medium irrigation to (70±5)% of soil relative moisture after jointing stage (W2), and adequate irrigation to (80±5)% of soil relative moisture after jointing stage (W3); and three levels of nitrogen: 0 kg ha^–1 (N1), 195 kg ha^–1 (N2) and
270 kg ha^–1 (N3).  Results showed that irrigation and nitrogen application significantly increased rhizosphere microorganisms and enzyme activities.  Soil microbiological properties showed different trends in response to N level; the highest values of bacteria, protease, catalase and phosphatase appeared in N2, while the highest levels of actinobacteria, fungi and urease were observed in N3.  In addition, these items performed best under medium irrigation (W2) relative to W1 and W3; particularly the maximum microorganism (bacteria, actinobacteria and fungi) amounts appeared at W2, 5.37×10⁷ and 6.35×10⁷ CFUs g^–1 higher than those at W3 in 2014–2015 and 2015–2016, respectively; and these changes were similar in both growing seasons.  Microbe-related parameters fluctuated over time but their seasonality did not hamper the irrigation and fertilization-induced effects.  Further, the highest grain yields of 13 309.2 and 12 885.7 kg ha^–1 were both obtained at W2N2 in 2014–2015 and 2015–2016, respectively.  The selected properties, soil microorganisms and enzymes, were significantly correlated with wheat yield and proved to be valuable indicators of soil quality.  These results clearly demonstrated that the combined treatment (W2N2) significantly improved soil microbiological properties, soil fertility and wheat yield on the Huanghuai Plain, China.

Water shortage has threatened sustainable development of agriculture globally as well as in the North China Plain (NCP).  Irrigation, as the most effective way to increase food production in dry land, may not be readily available in the situation of drought.  One of the alternatives is to supply plants with enough nutrients so that they can be more sustainable to the water stress.  The objective of this study was to explore effects of irrigation and sulphur (S) application on water consumption, dry matter accumulation (DMA), and grain yield of winter wheat in NCP.  Three irrigation regimes including no irrigation (rainfed, I₀) during the whole growth period, once irrigation only at jointing stage (90 mm, I₁), and twice respective irrigation at jointing and anthesis stages (90 mm plus 90 mm, I₂), and two levels of S application including 0 (S₀) and 60 kg ha^–1 (S₆₀) were designed in the field experiment in NCP.  Results showed that increasing irrigation times significantly increased mean grain yield of wheat by 12.5–23.7% and nitrogen partial factor productivity (NPFP) by 21.2–45.0% in two wheat seasons, but markedly decreased crop water use efficiency (YWUE).  Furthermore, S supply 60 kg ha^–1 significantly increased mean grain yield, YWUE, IWUE and NPFP by 5.6, 6.1, 23.2, and 5.6% (across two wheat seasons), respectively.  However, we also found that role of soil moisture prior to S application was one of important greater factors on improving the absorption and utilization of storage water and nutrients of soil.  Thus, water supply is still the most important factor to restrict the growth of wheat in the present case of NCP, supplying 60 kg ha^–1 S with once irrigation 90 mm at the jointing stage is a relatively appropriate recommended combination to improve grain yield and WUE of wheat when saving water resources is be considered in irrigated wheat farmlands of NCP.

The current interest in the health benefits of whole wheat grain has prompted breeders to further increase the concentration of antioxidants in wheat. The objective of this study was to investigate the variation in antioxidant content among Chinese wheat grains and the relationship between antioxidants and grain color and morphological characteristics. A wide variation was observed in the total phenolic, carotenoid and flavonoid contents, as well as the antioxidant activity (AOA), of Chinese wheat varieties. Black wheat had the highest mean total phenolic, carotenoid and flavonoid contents and the highest AOA, followed by red and white wheats. The grain color parameters were significantly negatively correlated with total phenolic, carotenoid and flavonoid contents and AOA among all of the wheat varieties examined, and grain weight was also significantly negatively correlated with these traits. The same correlation between grain weight and antioxidant traits was also observed within individual groups of wheat, which indicates that grain weight may be used as an index for selecting wheat varieties with high AOA. Landraces had significantly higher flavonoid content than commercial wheat varieties. The results of this study may be useful for breeding nutrient-rich wheat varieties.