Identifying the agronomic optimal plant density (AOPD) for maximum grain yield is essential to develop enhanced management strategies for maize (Zea mays L.) production. In this study, we used a boundary-line method to examine the yield response of maize to plant density in China, based on the metadata (2783 data points) gathered from 157 recent studies during 2000-2017. We found the AOPD was 8.5 × 10 4 plants ha −1 in Northeast China, 9.3 × 10 4 plants ha −1 on the North China Plain, 10.5 × 10 4 plants ha −1 in Northwest China, and 8.0 × 10 4 plants ha −1 in Southwest China. Compared with current practices, potential grain yield with these AOPDs was improved by 13-20% for these major maize regions of China. Across regions, AOPDs were similar for spring-planted (9.2 × 10 4 plants ha −1 ) and summer-planted maize (9.3 × 10 4 plants ha −1 ) systems, although grain yield at the AOPD was 7% greater for the spring-planted maize system. For different productivity environments, we found that high-yielding plots obtained a yield of 18.2 Mg ha −1 at an AOPD of 11.6 × 10 4 plants ha −1 , whereas in general productivity plots, 39% lower grain yield was achieved with a 19% lower AOPD (9.4 × 10 4 plants ha −1 ). In summary, this study illustrated AOPDs with modern maize hybrids for different productivity environments, cropping systems, and regions. Further study is needed to investigate the possible influence of agronomic factors such as lodging risks by increasing plant density.Abbreviations: AOPD, agronomic optimal plant density; LAI, leaf area index; NCP,
Germination heterochrony refers to germination of seeds dispersed in a single growing season, which is different from delayed germination. We studied two year’s demographic characteristics, characteristics of fruit heteromorphism, the relationship between fruit heteromorphism and germination heterochrony, effects of moisture and temperature on germination characteristics, as well as seed longevity of four annual Salsola L. species to analyze the adaptive significance and causes of germination heterochrony. We found that the number of individuals of all populations changed drastically in one year. Approximately 41.6–100% of seedlings germinated in spring died. The number of fruit types varied with interspecies and intraspecies. Despite the wide range of germination temperature of different fruit types (0–35 °C), the germination percentage at 0–15 °C was the highest. When the soil moisture content was 20%, the germination percentage was the highest, reaching 50% within the shortest time. The contrary was the case with the decreasing of soil moisture. The seed longevity of the four species was one year. Fruit heteromorphism had no direct relationship to germination heterochrony. Germination heterochrony was caused by precipitation characteristics and short seed longevity of annual Salsola L., which was an effective survival strategy for plant to adapt to the changing environments in arid area.
Population growth and economic development in China has increased the demand for food and animal feed, raising questions regarding China’s future maize production self-sufficiency. Here, we address this challenge by combining data-driven projections with a machine learning method on data from 402 stations, with data from 87 field experiments across China. Current maize yield would be roughly doubled with the implementation of optimal planting density and management. In the 2030 s, we estimate a 52% yield improvement through dense planting and soil improvement under a high-end climate forcing Shared Socio-Economic Pathway (SSP585), compared with a historical climate trend. Based on our results, yield gains from soil improvement outweigh the adverse effects of climate change. This implies that China can be self-sufficient in maize by using current cropping areas. Our results challenge the view of yield stagnation in most global areas and provide an example of how food security can be achieved with optimal crop-soil management under future climate change scenarios.
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