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The excessive application of nitrogen (N) fertilizer can result in soil and water pollution, thereby negatively impacting the ecological environment. However, reducing the amount of N fertilizer may lead to a decrease in crop yield. Two years' experiment (2021 and 2022) investigates the influence of one-time reduced basal application of controlled-release N fertilizer (CRU) and increased planting density on the grain yield and N utilization characteristics of mechanically transplanted japonica rice. Nanjing 5718 was used as the experimental material. Under the condition of 225 kg ha−1 of N, three controlled-release periods of CRUs (60d, 80d, 100d) and three planting densities (6, 8, and 10 seedlings/hole) were combined, totaling nine combinations. Moreover, a conventional split fertilization treatment with 300 kg ha−1 of N and a planting density of 4 seedlings/hole was set as the control (CK). The yield, dry matter accumulation, N accumulation, and N utilization efficiency were evaluated. The research findings demonstrate that the CRU80-6 treatment exhibited the highest efficacy among all N reduction and density increase treatments, resulting in a significant yield increase of 3.1–10.3% compared to other treatments. After the jointing stage, the CRU80-6 treatment exhibited the highest dry matter accumulation compared to other treatments, with an increase ranging from 0.8% to 13.6%, and was significantly lower than that of the CK by 4.3% to 5.0%. The N accumulation and translocation traits of the CRU80-6 treatment closely resembled those of CK. However, both N recovery efficiency (NRE) and N agronomic efficiency (NAE) exhibited a remarkable increase compared to CK, with an average enhancement in NRE of 30.01%. Therefore, we contend that the CRU80-6 treatment, with a 25% reduction in N input, can ensure efficient N utilization and attain a relatively stable grain yield. [ABSTRACT FROM AUTHOR]

As one of the world's principal food crops, rice sustains over half of the global population. With global climate change intensifying, the frequency of extreme high temperatures is increasing, posing significant threats to the growth and development, yield, and quality of rice, thereby jeopardizing global food security. This study reviews the impacts of high temperatures on rice at different developmental stages and summarizes previous research on heat tolerance cultivation techniques for rice. Currently, to enhance heat tolerance in rice, the following strategies were primarily adopted: (1) the exploration of heat-tolerant genetic resources and breeding of heat-tolerant varieties; (2) cooling through canopy temperature management via enhanced transpiration regulated by water management; (3) the scientific application of fertilizers to promote the accumulation of assimilates in rice; (4) the application of exogenous regulators to bolster the antioxidant capacity of rice. The implementation of these strategies not only helps to ensure rice yield and quality but also provides robust support for addressing the challenges that global warming poses to agricultural production. [ABSTRACT FROM AUTHOR]

This study investigated the differences in appearance quality among different soft japonica rice varieties based on grain shape, with a particular focus on the broad-ovate soft japonica rice varieties Nanjing 9108 and Nanjing 5718, as well as the slender soft japonica rice varieties Shangshida 19 and Jiahe 218, all sourced from the Yangtze River Delta. The results showed that the slender soft japonica rice varieties exhibited significantly superior appearance quality compared to the broad-ovate varieties. In the case of superior grains, the chalky grain rate of the broad-ovate soft japonica rice was 4307.79 percent higher than that of the slender varieties, and the degree of chalkiness was 8275.00 percent higher. For inferior grains, the chalky grain rate of the broad-ovate soft japonica rice was 238.34 percent higher than the slender varieties, and the degree of chalkiness was 339.96 percent higher. In contrast to the slender soft japonica rice, the broad-ovate varieties had a lower percentage of high-weight grains and a higher percentage of low-weight grains. Compared to the broad-ovate soft japonica rice, the slender varieties exhibited a faster grain-filling rate and shorter effective grain-filling days. Correlation analysis revealed that chalkiness had a significant negative correlation with grain length and aspect ratio. Simultaneously, chalkiness also showed a positive correlation with the number of effective grain-filling days while demonstrating a negative correlation with both the maximum and average grain-filling rates. The slender soft japonica rice exhibited a lower likelihood of developing chalkiness and higher grain-filling efficiency and developed a favorable grain weight distribution. These distinctive attributes significantly contribute to the superior appearance quality of the slender japonica soft rice. [ABSTRACT FROM AUTHOR]

Leptochloa chinensis (L.) Nees is a troublesome rice weed. We collected 242 L. chinensis populations from rice fields in eastern China and studied the duration of seed dormancy and the seed germination ability at different temperatures. All L. chinensis populations studied exhibited seed dormancy. The periods required to reach 50% germination under optimal conditions were 31–235 days, with an average of 96 days. None of the populations germinated at 15 °C. Under constant temperatures of 20, 25, 30, and 35 °C, the average germination percentages of 242 populations were 0%, 71%, 79%, and 60% at 2 days after treatment (DAT), and were 56%, 84%, 88%, and 88% at 14 DAT, respectively. The duration of seed dormancy, as well as the germination ability of seeds, were significantly (p < 0.05) influenced by the agricultural region and the longitude and latitude of the collection locations. Under constant temperatures of 20 to 35 °C, the average germination percentages of seeds collected from transplanted rice fields were significantly higher than those collected from direct-seeded fields. This is the first study on seed germination biology of L. chinensis with multiple populations systematically collected from rice fields on a regional scale. [ABSTRACT FROM AUTHOR]

This study addresses the uncertainty regarding the potential of a one-time basal application of mixed nitrogen (N) fertilizer to optimize both yield and eating quality of late-maturing medium japonica rice Nangeng 9108 and Fenggeng 1606 in the Yangtze River Delta. Six distinct combinations of blended N fertilizers were evaluated, with conventional split fertilization serving as the control. The blended formulations combined controlled-release N fertilizer (CRNF) and quick-acting N fertilizer (CNF) at a 1:1 ratio. Furthermore, the CRNF component was a combination of two CRNF types with varied N-release durations at a 4:1 ratio, leading to treatments labeled A1, A2, B1, B2, C1, and C2. Over a 2-year study, treatments B1, B2, C1, and C2 matched or surpassed the control in grain yield, with C1 and C2 yielding 2.83–4.85% more. Among the above high-yield treatments, C1 showcased the best rice eating quality, which exhibited increased peak viscosity, hot viscosity, cool viscosity, breakdown, and taste value of milled rice, and a decrease in rice protein content (PC). This enhancement in quality correlated with N accumulation patterns and their interplay with sink capacity. Specifically, a higher N accumulation resulted in a robust sink capacity under the C1 treatment, thus reducing N availability per unit sink capacity (NAV) and rice PC, ultimately enhancing the overall palatability of milled rice. Conclusively, the C1 fertilizer blend demonstrates potential in concurrently boosting yield and eating quality of late-maturing medium japonica rice in the region. [ABSTRACT FROM AUTHOR]

Unmanned aerial seeding (UAS) is an efficient unmanned rice planting method with broad application prospects. But its optimum basic seedling number and yield and quality characteristics remain unclear. Field experiments were conducted to compare UAS, unmanned dry direct seeding (UDDS), and unmanned carpet transplanting (UCT) methods using inbred japonica rice variety Nanjing 5718. The UAS method was subdivided into four planting density treatments (UAS105, UAS150, UAS195, and UAS240 = 105, 150, 195, and 240 seedlings/m2, respectively). The results showed that increasing the basic seedling density first increased the yield but then it decreased, and UAS195 produced a significantly higher yield. On the other hand, the grain processing, appearance, and taste quality deteriorated with improved nutritional quality. Among the three planting methods, UAS (UAS195) yielded less than UCT due to there being fewer spikelets per panicle, a lower grain-filling rate, and less photosynthetic activity after heading. However, UAS (UAS195) produced more yields than UDDS by having more panicles, more spikelets per panicle, and more biomass accumulation. Both UAS195 and UDDS had poorer grain processing, appearance, and nutritional quality than UCT, but increased amylose content and taste values. Therefore, UAS195 could be an alternative planting method for inbred japonica rice with coordinated yield, quality, and production efficiency. [ABSTRACT FROM AUTHOR]

The effects of temperature and solar radiation on milling and appearance quality of rice (Oryza sativa L.) were evaluated to find the optimal temperature and solar radiation for optimizing milling and appearance quality of rice in the lower reaches of Huai River. Field experiments were conducted with two medium-maturing japonica soft rice varieties (SMR), two late-maturing japonica soft rice varieties (SLR) and two late-maturing japonica non-soft rice varieties (LR) as experimental materials. Seeds were sown on 10 May (T1), 17 May (T2), 24 May (T3), 31 May (T4), 7 June (T5), 14 June (T6), and 21 June (T7) in 2017 and 2018. Compared with solar radiation, temperature was the main environmental factor affecting the milling and appearance quality of rice in the lower reaches of Huai River. Under the condition of ensuring relatively high-yield, the milling quality of SMR and SLR can reach the second grade of China's national standard of high quality paddy. The mean daily temperature (Tmean) range were 20.2–22.7 °C and 20.4–22.0 °C respectively. The temperature range for LR to obtain a relatively high-yield, good milling and appearance quality was 20.4–20.7 °C. The optimal sowing dates of SMR, SLR and LR were 15 May to 1 June, 15 May to 20 May and 15 May to 20 May, respectively. [ABSTRACT FROM AUTHOR]