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This study explored the effects of the sowing stage and nitrogen application rate on the grain yield and its allocation of light-temperature resources over a 9-year experiment from 2011 to 2019. Measurement indicators include the effective accumulative temperature on different growth durations, leaf area index (LAI), above-ground biomass production, and harvest index (HI). Methods: A split-plot design was arranged in the treatment, with N supply as the main plot and the sowing stage as the subplot. The main plots consisted of two nitrogen treatments: low nitrogen (LN: 120 kg ha−1) and high nitrogen (HN: 180 kg ha−1). The subplots contained two sowing stages: the early sowing stage (ES) and the late sowing stage (LS). Results: Compared with LNLS, LNES, and HNLS from 2011 to 2019, HNES of HHZ increased the grain yield by 9.5%, 2.5%, and 5.3%, while the difference in grain yield in YY8 was higher than HHZ, especially under HNES. Compared with LNLS, LNES, and HNLS from 2011 to 2019, HNES of HHZ increased the panicle number by 6.0%, 5.9%, and 1.0%, and HNES of YY8 increased by 12.7%, 11.4%, and 3.8%. Compared with HNLS of HHZ, LNES, LNLS, and HNES decreased the spikelets per panicle by 2.3%, 2.9%, and 1.1%, and decreased by 3.5%, 1.9%, and 2.2% in YY8. The early sowing or increasing N supply significantly increased the dry matter accumulated, grain weight, LAI, and HI. The higher grain yield in LNES was more closely related to the average temperature and the number of spikelets per panicle. The grain yield in HNES was more dependent on the effective accumulative temperature. Conclusions: Sowing in mid-May and increasing the N application (180 kg ha−1) are beneficial to the allocation of light temperature and the increase in yield. Therefore, this research provides a theoretical basis for improving rice yield and optimizing the utilization of light-temperature resources in the future. [ABSTRACT FROM AUTHOR]

In wheat production, improving resource utilization and grain yield is the goal researcher have been pursuing. This study aimed to investigate if a regulated nitrogen (N) and selenium (Se) fertilizer management could increase wheat yield and N use efficiency (NUE). This study reports the effects of three N application levels (N0: 0 kg N ha−1, N1: 180 kg N ha−1, N2: 270 kg N ha−1) and a combination of three Se application levels (Se0: 0 g Se ha−1, Se1: 450 g Se ha−1, Se2: 900 g Se ha−1) on N metabolism, NUE and yield in wheat in 2020–2021. Compared with N0, wheat yield increased by 44.76% in N1 and by 54.32% in N2, and the activity of N-metabolizing enzymes increased by 25.15~35.03% in N1 and by 32.01~51.27% in N2. Compared with N1, the apparent recovery efficiency of N, the agronomic N use efficiency and the partial factor productivity of applied N decreased by 15.71%, 28.00% and 28.93% in N2, respectively. Compared with Se0, the 1000-grain weight increased by 3.93% in Se1 and by 4.87% in Se2, and the activity of nitrogen-metabolizing enzymes increased by 4.23~4.91% in Se1 and by 6.65~8.46% in Se2. We conclude that Se could improve the wheat 1000-grain weigh and N metabolism and has the potential to increase wheat yield and NUE. [ABSTRACT FROM AUTHOR]

Nitrogen fertilizer and planting density are key factors affecting rice yield and nitrogen utilization efficiency. There is still a need to optimize nitrogen fertilizer and planting density management for high yield. We studied the effects of different quantities of nitrogen application (N0 0 kg ha−1, N1 120 kg ha−1, N2 180 kg ha−1) and planting density (low-density: 18.8 hills m−2; high-density: 37.5 hills m−2) on rice yield, photosynthetic characteristics, antioxidant system, and nitrogen use efficiency. ANOVA results indicated that most tested traits were affected by environment, planting density, N application, and their interactions. Comparing the results of low-density planting, high-density planting increased the panicle number by 21.12% but decreased the grain number per panicle and yield by 3.97% and 22.48%, respectively. Similarly, the superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) activities and PFPn (partial factor productivity of nitrogen) decreased by 8.20%, 6.99%, 16.41%, 14.28%, and 5.73%, respectively, while HIn (N harvest index) increased by 1.32%. Compared to no N application, N application treatments increased the panicle number, grain number per panicle, and yield by 9.92%, 17.64%, and 37.83% in the N1 treatment; and increased by 17.15%, 29.09%, and 128.94% in the N2 treatment, respectively. N application significantly increased net photosynthetic rates and enzyme activities of antioxidant antioxidases. Compared with N1, N2 decreased REn (apparent recovery efficiency of N), AEn (agronomic N use efficiency), and PFPn by 8.98%, 11.80%, and 25.14%, respectively, while, compared with N0, N1 increased HIn by 8.50%. It was observed that nitrogen fertilizer and planting density had an interaction effect on the net photosynthetic rate, antioxidant enzyme activities, and PFPn and HIn. Given a comprehensive consideration, it is best to apply nitrogen at a rate of 120 kg ha−1 at the planting density of 37.5 hills m−2 for high grain yield and high N use efficiency in our experimental site. [ABSTRACT FROM AUTHOR]