Tillage represents an important practice that is used to dynamically regulate soil properties, and affects the grain production process and resource use efficiency of crops. The objectives of this 3-year field study carried out in the Huang-Huai-Hai (HHH) Plain of China were to compare the effects of a new deep vertical rotary tillage (DVRT) with the conventional shallow rotary tillage (CT) on soil properties, winter wheat (Triticum aestivum L.) grain yield and water and nitrogen use efficiency at different productivity levels, and to identify a comprehensive management that optimizes both grain yield and resource use efficiency in the HHH Plain. A split-plot design was adopted in field experiments in the winter wheat growing seasons of 2016–2017 (S1), 2017–2018 (S2) and 2018–2019 (S3), with DVRT (conducted once in June 2016) and CT performed in the main plots. Subplots were treated with one of four targeted productivity level treatments (SH, the super high productivity level; HH, the high productivity and high efficiency productivity level; FP, the farmer productivity level; ISP, the inherent soil productivity level). The results showed that the soil bulk density was reduced and the soil water content at the anthesis stage was increased in all three years, which were due to the significant effects of DVRT. Compared with CT, grain yields, partial factor productivity of nitrogen (PFP_N), and water use efficiency (WUE) under DVRT were increased by 22.0, 14.5 and 19.0%. Path analysis and direct correlation decomposition uncovered that grain yield variation of winter wheat was mostly contributed by the spike numbers per area under different tillage modes. General line model analysis revealed that tillage mode played a significant role on grain yield, PFP_N and WUE not only as a single factor, but also along with other factors (year and productivity level) in interaction manners. In addition, PFP_N and WUE were the highest in HH under DVRT in all three growth seasons. These results provided a theoretical basis and technical support for coordinating the high yield with high resource use efficiency of winter wheat in the resource-restricted region in the HHH Plain of China.

Competition is a common phenomenon in agriculture production.  Research on the relationship between competitive ability and crop yield is extensive, but the results have been inconsistent.  Few studies have focused on the relationship between population competitive intensity and yield of maize (Zea mays L.) cultivars.  The main objective of this study was to determine if a consistent relationship exists between maize yield and competitive ability.  A two-year field experiment was conducted, employing a de Wit replacement series design.  When two maize cultivars were grown in a mixture, yield was reduced for the modern cultivar and increased for the older cultivar.  In each replacement series, per plant level yield of each cultivar, and population level yield of the mixture, decreased with increasing proportion of the older cultivar.  Competitive ratio (CR) reflected differences in competitive ability of the three maize cultivars.  In each replacement series, population competition pressure (PCP) increased with increasing proportion of the older cultivar, indicating that the older cultivar was a strong competitor.  Biomass yield, grain yield, harvest index, thousand-kernel weight, and kernel number per plant, were negatively correlated with PCP.  Our results demonstrated that inter-cultivar competition affects maize productivity, and increasing PCP will decrease translocation of assimilates to grain and, ultimately, reduce yield.  Therefore, there is a negative correlation between population competitive intensity and yield performance in maize, breeders should develop a communal ideotype that would not perform well in competition in future.