Grain zinc (Zn) and iron (Fe) concentrations and their responses to foliar application of micronutrients in 28 Chinese wheat landraces and 63 cultivars were investigated in a two-year field experiment.  The average grain Zn and Fe concentrations were 41.8 mg kg^–1 (29.0−63.3 mg kg^–1) and 39.7 mg kg^–1 (27.9−67.0 mg kg^–1), respectively.  Compared with cultivars, landraces had greater grain Zn (11.0%) and Fe (4.8%) concentrations but lower harvest index (HI), grain weight per spike (GWS), grain number per spike (GNS) and thousand grain weight (TGW).  Both Zn and Fe concentrations were negatively and significantly correlated with HI, GWS, and GNS, while showed a poor association with TGW, suggesting that lower HI, GWS, and GNS, but not TGW, accounted for higher Zn and Fe concentrations for landraces than for cultivars.  Grain Zn concentrations of both cultivars and landraces significantly increased after foliar Zn spray and the increase was two-fold greater for landraces (12.6 mg kg^–1) than for cultivars (6.4 mg kg^–1).  Foliar Fe spray increased grain Fe concentrations of landraces (3.4 mg kg^–1) and cultivars (1.2 mg kg^–1), but these increases were not statistically significant.  This study showed that Chinese wheat landraces had higher grain Zn and Fe concentrations than cultivars, and greater increases occurred in grain Zn concentration than in grain Fe concentration in response to fertilization, suggesting that Chinese wheat landraces could serve as a potential genetic source for enhancing grain mineral levels in modern wheat cultivars.

We investigated the soil microbiologic characteristics, and the yield and sustainable production of winter wheat, by conducting a long-term fertilization experiment.  A single application of N, P and K (NPK) fertilizer was taken as the control (CK) and three organic fertilization treatments were used: NPK fertilizer+pig manure (T1), NPK fertilizer+straw return (T2), NPK fertilizer+pig manure+straw return (T3).  The results showed that all three organic fertilization treatments (T1, T2 and T3) significantly increased both soil total N (STN) and soil organic carbon (SOC) from 2008 onwards.  In 2016, the SOC content and soil C/N ratios for T1, T2 and T3 were significantly higher than those for CK.  The three organic fertilization treatments increased soil microbial activity.  In 2016, the activity of urease (sucrase) and the soil respiration rate (SRS) for T1, T2 and T3 were significantly higher than those under CK.  The organic fertilization treatments also increased the content of soil microbial biomass carbon (SMBC) and microbial biomass nitrogen (SMBN), the SMBC/SMBN ratio and the microbial quotient (qMB).  The yield for T1, T2 and T3 was significantly higher than that of CK, respectively.  Over the nine years of the investigation, the average yield increased by 9.9, 13.2 and 17.4% for T1, T2 and T3, respectively, compared to the initial yield for each treatment, whereas the average yield of CK over the same period was reduced by 6.5%.  T1, T2, and T3 lowered the coefficient of variation (CV) of wheat yield and increased the sustainable yield index (SYI).  Wheat grain yield was significantly positively correlated with each of the soil microbial properties (P<0.01).  These results showed that the long-term application of combined organic and chemical fertilizers can stabilize crop yield and make it more sustainable by improving the properties of the soil.

Two pot experiments were conducted to study the effects of root pruning at the stem elongation stage on non-hydraulic root-sourced signals (nHRS), drought tolerance and water use efficiency of winter wheat (Triticum aestivum). The root pruning significantly reduced the root weight of wheat, but had no effect on root/shoot ratio at the two tested stages. At booting stage, specific root respiration of root pruned plants was significantly higher than those with intact roots (1.06 and 0.94 mmol g-1 s-1, respectively). The soil water content (SWC) at which nHRS for root pruned plants appeared was higher and terminated lower than for intact root plants, the threshold range of nHRS was markedly greater for root pruned plants (61.1-44.6% field water capacity) than for intact root plants (57.9-46.1% field water capacity). At flowering stage, while there was no significant difference in specific root respiration. The SWCs at which nHRS appeared and terminated were both higher for root pruned plants than for intact root plants. The values of chlorophyll fluorescence parameters, i.e., the effective photosystem II quantum yield ( PS II), the maximum photochemical efficiency of PS II (Fv/Fm), coefficient of photochemical quenching (qP), and coefficient of non-photochemical quenching (NPQ), in root pruned plants were significantly higher than in intact root plants, 7 d after withholding of water. Root pruned plants had significantly higher water use efficiency (WUE) than intact root plants in well-watered and medium drought soil, but not in severe drought condition. In addition, root pruning had no significant effect on grain yield in well-watered and medium drought soil, but significantly decreased grain yield in severe drought condition. In conclusion, the current study showed that root pruning significantly altered nHRS sensitivity and improved WUE of winter wheat in well-watered and medium drought soil, but lowered drought tolerance of winter wheat in severe drought soil. This suggests a possible direction of droughtresistance breeding and potential agricultural measure to improve WUE of winter wheat under semiarid conditions.