The assessment and control of losses of nitrogen (N) and phosphorus (P) from paddy fields is critical to improve the quality of water and atmosphere on earth. A field experiment was conducted to investigate the effect of three N managements (local common N fertilization practice, urea mixed with controlled-release N fertilizer, and optimized and reduced N fertilizer, designated CN, U + CRF and ON, respectively) on N and P losses through runoff and leaching from a paddy field, and yield of rice under shallow-irrigation and deep-sluice (SIDS) and continuous flooding irrigation (FI) in the Jianhan Plain of China in 2016. The results showed that, compared with FI, SIDS significantly reduced the frequency of irrigation and amount of irrigation water, resulting in an increase of 16.2% in rainfall use efficiency, and therefore, a reduction in the amount of surface runoff and water that had leached. This was responsible for the decreased total N (TN) and total P (TP) losses through runoff leaching under SIDS. The U + CRF and ON treatments resulted in a significant reduction in losses of TN through runoff and leaching and the loss of TP through leaching compared to CN. SIDS resulted in comparable or greater soil TN and TP contents in the 0–40 cm soil depths after rice harvest; N and P accumulation at the jointing, filling and maturity stages; and yield of grain compared to FI. Moreover, the U + CRF and ON improved or maintained accumulation of N and P and yield of rice compared to CN. Compared with FI coupled with CN, SIDS coupled with the U + CRF or ON treatments significantly reduced losses of N and P from paddy fields and enhanced or maintained the accumulation of N and P and yield of rice grains. In conclusion, SIDS coupled with the new N management could be an effective approach to reduce losses of N and P from paddy fields and would be a positive improvement for high yield of middle-season rice grains in the Jianhan Plain of central China and other regions with similar environments.

Cadmium (Cd) contamination in agricultural soils has become a serious issue owing to its high toxicity threat to human health through the food chain. The purpose of this paper is to explore the availability of foliar selenium (Se) application in reducing Cd enrichment in brown rice. A field experiment from 2017 to 2019 was conducted to investigate the effects of foliar Se application on the physiology and yields of three rice cultivars and their accumulation of Cd in low-Cd and high-Cd soils. The grain protein contents and yields of rice plants grown in the high-Cd soil were lower than those of plants cultivated in the low-Cd soil by 27.85% and 6.82%, whereas the malondialdehyde (MDA) and Cd contents were higher by 66.06% and 91.47%, respectively. Se application reduced Cd translocation from the stems and leaves to the spikes, decreasing the Cd content in brown rice by 40.36%. Additionally, Se enhanced the antioxidative activity, glutathione and protein contents, and rice yield (7.58%) and decreased the MDA and proline contents. However, these Se effects weakened under the high-Cd soil. Foliar Se application can alleviate Cd-induced physiological stress in brown rice while improving its yield and reducing its Cd content.

The Chinese government regards ensuring food security and developing water‐saving agriculture as an important national strategy and that carrying out relevant research has important practical significance and production application value. A two‐year field experiment was conducted to explore the compensation potential in rice yield by using rice varieties with different panicle size under two water management regimes (conventional water management or CWM and alternate wetting and drying or AWD). The results showed that the large panicle rice variety resulted in greater yield, crop water productivity, spikelet density, dry matter accumulation and translocation, and photosynthesis. Compared with the CWM, the AWD had little effect on rice yield. However, with an appropriate planting density, the AWD achieved a greater grain yield compared with the CWM. Moreover, the AWD increased crop water productivity and the grain‐filling efficiency. The loss of spikelets under the AWD could be compensated by increasing the planting density. Although AWD reduced tillering number, it increased the photosynthetic rate, dry matter accumulation and its translocation to grain, and leaf area index. In addition, the adverse effects on rice growth and the yield caused by the AWD could be alleviated by increasing planting density of rice. Therefore, an appropriate planting density can be used to save water and maintain high grain yield of rice under alternate wetting and drying.

Optimizing the sowing date of rice can change the seasonal patterns and distributions of climate factors during the crop growing season, making it one of the most effective ways to adapt to climate change and achieve high yield. A four–year field experiment (2018–2021) was conducted at Jingzhou Agricultural Meteorological Experiment Station, central China, with four different sowing dates (SD) each year, late April (SD1), early May (SD2), mid–May (SD3) and late May (SD4). Dry matter accumulation, grain yield and climate conditions were observed across sowing dates. Our findings revealed that delaying the sowing date from early May to mid or late May could increase grain yield by 5.6% to 8.6%. However, sowing too early could increase heat stress, decrease the net effective accumulated temperature, inhibit rice growth, and reduce grain yield. On the other hand, sowing too late could increase the risk of low temperatures after flowering. From the perspective of increasing net effective accumulated temperature, reducing heat stress and low temperature after flowering, mid to late May was the most favorable sowing date to ensure high yield. It is suggested that optimizing rice sowing dates can effectively avoid the threat of heat stress and better match thermal resources, thereby increasing rice productivity.

Feed input leads to a large amount of nitrogen-containing sediment accumulating in the substrate in the pond culture process, threatening the safety of aquaculture production. Planting lotus roots (Nelumbo nucifera Gaertn.) in ponds can accelerate the removal of bottom nitrogen, while the role of nitrogen cycle-related microorganisms in the removal is still unclear. In this study, eight yellow catfish (Pelteobagrus fulvidraco) culture ponds with the same basic situation were divided into fishponds with planted lotus roots and ponds with only fish farming. Sediment samples were taken from the fishponds with planted lotus roots and the ponds with only fish farming before and after fish farming, marked as FPB, FPA, FOB, and FOA, respectively, and subjected to physicochemical and metagenomic sequencing analyses. The results show that the contents of NH₄⁺, NO₂⁻, TN, TP, and OM were significantly lower (p < 0.05) in FPA than in FOA. The abundance of metabolic pathways for inorganic nitrogen transformation and ammonia assimilation increased considerably after culture compared to the sediments before culture. A total of eight ammonia production pathways and two ammonia utilization pathways were annotated in the sediments of the experimental ponds, with a very high abundance of ammonia assimilation. Acinetobacter and Pseudomonas (34.67%, 18.02%) were the dominant bacteria in the pond sediments before culture, which changed to Thiobacillus (12.16%) after culture. The FPA had significantly higher relative abundances of Thiobacillus denitrificans and Sulfuricella denitrificans, and the FOA had significantly a higher abundance of Microcystis aeruginosa compared to other samples. The massive growth of Microcystis aeruginosa provided two new inorganic nitrogen metabolic pathways and one organic nitrogen metabolic pathway for FOA. The relative abundances of these three microorganisms were negatively correlated with NH₄⁺ content (p < 0.01) and significantly positively correlated with AP, OM content, and pH value. Compared with ponds with only fish farming, lotus root–fish co-culture can significantly reduce the nitrogen content in sediment, increase the abundance of denitrifying bacteria, and inhibit algae growth. Still, it has little effect on the abundance of nitrogen cycle-related enzymes and genes. In summary, it is shown that, although lotus roots promote the growth of denitrifying microorganisms in the sediment, nitrogen removal relies mainly on nutrient uptake by lotus roots.