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Although there are many new types of environmentally friendly fertilizers that can improve maize yield, chemical fertilizers are the most widespread type of fertilizer used in the agricultural sector of China due to their low cost and ease of application. However, the misuse of chemical fertilizers could lead to environmental problems, such as the massive emission of greenhouse gases (GHG). Therefore, it is important to determine how fertilizer-use efficiency (FUE) could be improved to stabilize or increase maize yield while reducing GHG emissions. In this study, we collected 6618 date records which include three datasets (for N, P, and K) from five maize-growing regions in China from 2005 to 2018, and performed a meta-analysis on the effects of N, K, and P fertilization levels on maize yield, partial factor productivity (PFP), agronomic efficiency (AE), and the carbon footprint of maize production. Additionally, scenario analyses were performed to estimate optimal fertilizer application rates for stabilizing or increasing maize yield while reducing GHG emissions. It was shown that FUE and maize yield responses to fertilization level varied in different regions. Compared to the past, the maize production of China has improved significantly in terms of FUE and its carbon footprint in recent years. Because of improvements in maize cultivars and cultivation technologies, it is possible to decrease N, P, and K application rates and reduce per unit area carbon footprint of maize, without compromising yield. In the future, N fertilization should be reduced by 10% from current levels, and the application of P and K fertilizers should be increased or decreased depending on the conditions of each maize-growing region. Thus, it should be possible to stabilize or even increase yields and reduce GHG emissions of maize production, thereby achieving green and efficient development. [ABSTRACT FROM AUTHOR]

Ecological factors affect maize growth and development, and induce stalk lodging. Studying the effects of ecological factors on the stalk lodging within dense planting maize is essential to develop field management strategies. To investigate the response of stalk lodging resistance to density and ecological site. To identify the key ecological factors affecting lodging. This study conducted field experiments in 2019–2020 at 6 sites in Southwest China, with 6 densities (3.0, 4.5, 6.0, 7.5, 9.0 and 10.5 × 104 plants hm−2) to determine the variation in lodging rate and stalk lodging resistance traits. The dense planting reduced stalk lodging resistance and varied among ecological sites. Plant morphology exhibited relatively high stability, with coefficients of variation (CV) of 0.01143–0.1097. Bending strength and dry matter constituents of basal internodes were more sensitive (CV: 0.1425–0.4446) compared to other traits, while the density effect was more significant. The extreme weather and stalk lodging resistance index jointly determined lodging, with lodging lowest at high stalk lodging resistance index (≥1.367) and low frequency of extreme weather events (＜14.40 %). Among the internode traits, the dry matter constituents contributed more than 55.0 % to mechanical strength. In addition, internode diameter was important for bending strength, while skin group was for rind penetration strength. Altitude or net solar radiation explained 28.70 % or 21.10 % of the mechanical strength, being the most important ecological factor. Maize stalk lodging resistance decreased with dense planting and also influenced by ecological factors, but the response of different stalk lodging resistance traits to density and ecological site. The higher altitude and net solar radiation favored higher internode mechanical strength, resulting in greater stalk lodging resistance. The lower frequency of extreme weather events and higher stalk lodging resistance index resulted in a lower lodging rate. The selection of maize hybrids with high internode plumpness, cellulose and lignin content in the basal internodes and less affected by density and ecological sites, can enhance stalk lodging resistance and its stability. The appropriate planting density should match the ecological conditions of the site. [ABSTRACT FROM AUTHOR]

Using low nitrogen (N)–tolerant maize varieties serves as a viable means to curtail N fertilizer application while improving crop yield. To investigate the differences in carbon and nitrogen metabolic processes, and the hormones within kernels located at varying positions along the ear, between low N–tolerant and low N–sensitive maize varieties. Furthermore, this research aims to elucidate the ramifications of these observed disparities on kernel weight and yield, particularly when cultivated under low N conditions. The low N–tolerant maize variety (ZH311) and low N–sensitive maize variety (XY508) were applied. The in–situ filed experiment with three N fertilizer treatments of 0 N (0 kg·N ha−1), 150 N (150 kg·N ha−1) and 300 N (300 kg·N ha−1) was conducted in 2017–2019. The apical kernel weight of ZH311 was less affected by low N (0 N and 150 N) and the yield was 25.3–22.9% higher than XY508. The kernel weight was significantly and positively correlated with kernel starch and protein content. The starch and protein contents of ZH311 apical kernels were 6.3–7.3% and 12.4–14.4%, higher than XY508 under low N. It was indicated that the main factor affecting starch accumulation in the apical kernels was Susy activity and protein accumulation was IAA/GA 3 , Z+ZR/GA 3 and GOGAT activity by the redundancy analysis. Under low N, the Susy and GOGAT activity, IAA/GA 3 and Z+ZR/GA 3 in the apical kernel of ZH311 were higher than XY508 by 51.4–39.3% and 65.4–46.9%, 62.1–33.1% and 41.8–48.2%. We have demonstrated to improve the maize yield by increasing the apical kernel weight, which resulted in enhancing the uniformity of the kernel weight along the ear. Under low N conditions, the low N–tolerant maize variety was shown to facilitate the starch and protein biosynthesis by increasing the activity of key enzymes in the carbon and the nitrogen metabolism processes such as Susy and GOGAT in the apical kernels, and optimizing the hormone balance between IAA/GA 3 and Z+ZR/GA 3 , to increase the kernel weight and yield. The findings of this investigation will help understand the underlying factors contributing to the yield variations exhibited among distinct low N–tolerant maize varieties when cultivated under conditions of limited N availability. These insights could serve as the theoretical basis for breeding of low N–tolerant maize varieties and practical guidance for the formulation of N fertilizer management strategies. [Display omitted] • Apical kernel weight and grain yield of ZH311 were less affected by low N stress. • Apical kernels of ZH311 had more starch and protein content under low N conditions. • Higher Susy activity promoted starch formation in the apical kernels of ZH311. • Optimized hormone balance and GOGAT activity in the apical kernels of ZH311 promoted protein synthesis. [ABSTRACT FROM AUTHOR]

Enhancing the basal internode mechanical strength by improving the canopy light distribution of dense planting maize to reduce the lodging rate is important for establishing a high-yielding and stable population. A three-year field experiment was carried out at three densities treatments (5.25 × 104, 6.75 × 104 and 8.25 × 104 plants hm−2) × four nitrogen fertilizer treatments (0, 120, 180 and 240 kg hm−2) to study canopy light distribution and stalk lodging resistance characteristics. Results showed that grain yield was increased 3.31–14.68% under 6.75 × 104 plants hm−2 treatment compared to 5.25 × 104 plants hm−2. Meanwhile, plant morphology was altered with the increasing of planting density, light interception rate at lower-middle canopy position (0–150 cm) was decreased 15.10%, thus the mechanical strength of the basal internodes was reduced, and the lodging rate was increased 4.66% points. The formation of maize stalk lodging resistance and grain yield was promoted by the nitrogen fertilizer application. The N 180 treatment improved mechanical strength by enhancing canopy light distribution and optimizing internode quality, lodging rate was decreased 6.31–17.22% compared to the N 240 treatment while only a 0.54–7.54% reduction in grain yield, finally. Analysis the relationship between characteristic factors and mechanical strength, we found that internode plumpness (explained the 85.6% percentage of variability) was the key factor affecting basal internode mechanical strength. Our results will assist breeders in breeding lodging-resistant hybrids and agronomists improving field management practices for low lodging rate and high yield, and will be equally illuminating for other maize-producing regions. • The lower-middle canopy position light interception rate affected internode mechanical strength. • Nitrogen fertilizer management optimized canopy light distribution affecting stalk lodging resistance. • Internode plumpness was the key factor affecting internode mechanical strength. [ABSTRACT FROM AUTHOR]

Stalk lodging in maize causes yield and quality losses worldwide. This could potentially be prevented through breeding and improved crop management. Breeding efforts and management optimization are however, hampered by the lack of an internode growth model and an indicator for stalk lodging resistance. With this study, we aim to contribute to a solution for this problem. We report on the results of a two-year field study in which we measured and analyzed plant traits assumed to be related to stalk lodging resistance, in five cultivars. These traits include plant and basal internode morphology, dry matter constituents accumulation, and mechanical strength of basal internode. Results from a logistic regression analysis indicate that, the stalk lodging incidence was significantly affected by the development process of the basal internode. The rapid accumulation duration of lignin, internode plumpness and cellulose were found to be the most important contributors to mechanical strength of basal internode. The correlation between Rind penetration strength (PS) and stalk lodging rate was found to be higher than the correlation between bending strength (BS) and the stalk lodging rate. In addition, PS was found to be more stable than BS over development stages and years. Dry matter constituents accumulation in the basal internode, especially lignin accumulation, were found to be the dominant process determining the mechanical strength of the basal internode. Breeding and crop management strategies aiming to prolong the duration of rapid lignin and dry matter accumulation in the basal internode may thus significantly contribute to improved lodging resistance in future maize cultivars. • Growth parameters of morphology, dry matter constituents and mechanical strength were clarified for internodes growth model. • Dry matter constituents (especially lignin) accumulation in internodes was crucial for increasing stalk lodging resistance. • Mechanical strength of basal internodes was positively related to dry matter constituents' rapid growth duration. [ABSTRACT FROM AUTHOR]