Hong Shi

In recent years, there has been a notable increase in the frequency and intensity of floods and heavy rains, which has resulted in the frequent inundation of rice-growing areas. Flooding during the heading–flowering stages of early rice can result in significant yield losses. To elucidate the response of rice to sediment content, flooding, and drainage processes and their underlying mechanisms, a pot experiment was conducted to investigate the effects of sediment contents (S₁: 0, S₂: 0.10 kg m⁻³, and S₃: 0.25 kg m⁻³), flooding time (F₁: 3 days and F₂: 6 days), and drainage time (D₁: 3 days and D₂: 6 days) during the heading–flowering stage on the oxidation resistance and grain yield of early rice in the Poyang Lake Region. At the same time, an experimental control group (CK) was set up with no sediment, no flooding, or no drainage treatment. The results showed that the flag leaf area of S₁F₁D₂ treatment was diminished by flooding. The relative chlorophyll content (SPAD) reached its lowest value prior to drainage. The treatment of S₂F₂D₁ showed the greatest decrease in SPAD value of 41.57%, which was only 53.88% of that of the control treatment. The activity of superoxide dismutase (SOD), peroxidase (POD), and the content of malondialdehyde (MDA) were observed to increase during the flooding period in comparison to the control treatment. The maximum values for these parameters were recorded at 5.68, 3.09, and 1.9 times higher than those of the control treatment, respectively. However, a decrease was observed after drainage. Furthermore, the occurrence of flooding during the early rice heading–flowering stage resulted in a notable reduction in the grain number per spike and the fruiting rate, consequently leading to a considerable decline in grain yields, with a decrease ranging from 31.81% to 69.96%. The findings indicate that flooding during the heading–flowering stage resulted in a reduction in early rice grain yield yet enhanced the antioxidant capacity of the leaves. Regression analyses indicated that a prediction model for the actual yield after flooding stress at the heading–flowering stage of early rice could be constructed using SFW as the independent variable. The findings of this study provide a theoretical basis for the formulation of a scientific and reasonable drainage scheme with the objective of reducing yield loss following rice flooding in the southern rice-growing region of China.

Exploring the growth and physiological response mechanisms of rice under continuous drought stress circumstances can provide a significant scientific foundation and technological assistance for meeting drought difficulties, improving drought resistance and rice (Oryza sativa L.) output, and ensuring food security. In this study, a rice field experiment was conducted under a rain shelter with five different treatments set up: P1 (drought stress from tillering stage), P2 (drought stress from jointing–booting stage), P3 (drought stress from heading–flowering stage), P4 (drought stress from grain filling stage), and CK (adequate water management throughout the growth stage). Continuous drought stress from different growth stages with four levels (mild, medium, moderate, and severe). The results showed that the effects of different drought stress treatments on rice growth varied significantly. Compared with the CK treatment, plant height was reduced by 12.10%, 8.14%, 3.83%, and 1.06% in the P1, P2, P3, and P4 treatments, respectively, and the number of tillers was reduced by 23.83%, 18.91%, 13.47%, and 8.68%, respectively. With the increase in drought stress levels, SPAD values and Rubisco activity of rice leaf continued to decrease; SOD activity showed a decreasing trend, but the decreasing trend of POD and CAT activities was not significant, while MDA content showed an increasing trend. For yield components, continuous drought stress significantly reduced spike length of rice by an average of 3.5%, effective number of spikes by 18.9%, thousand grain weight by 3.7%, grain number per spike by 11.6%, and fruiting rate by 1.8%, respectively, compared to CK treatments during the growth period. In general, continuous drought stress during the early growth period affected the effective spike number and the grain number per spike. Continuous drought stress after the grain filling stage had the least effect on yield (17.62% of yield reduction), and water use efficiency (1.76 kg m⁻³) was much higher than other treatments. These researchers’ findings provide insight into how rice physiology and growth react to continuous drought stress, which is significant for agricultural operations.

Exploring the growth and physiological response mechanisms of rice under continuous drought stress circumstances can provide a significant scientific foundation and technological assistance for meeting drought difficulties, improving drought resistance and rice (Oryza sativa L.) output, and ensuring food security. In this study, a rice field experiment was conducted under a rain shelter with five different treatments set up: P1 (drought stress from tillering stage), P2 (drought stress from jointing-booting stage), P3 (drought stress from heading-flowering stage), P4 (drought stress from grain filling stage), and CK (adequate water management throughout the growth stage). Continuous drought stress from different growth stages with four levels (mild, medium, serious, and extreme). The results showed that the effects of different drought stress treatments on rice growth varied significantly. Compared with the CK treatment, plant height was reduced by 12.10%, 8.14%, 3.83%, and 1.06% in the P1, P2, P3, and P4 treatments, respectively; and the number of tillers was reduced by 23.83%, 18.91%, 13.47%, and 8.68%, respectively. With the increase in drought stress levels, SPAD values and Rubisco activity of rice leaf continued to decrease; SOD activity showed a decreasing trend, but the decreasing trend of POD and CAT activities was not significant, while MDA content showed an increasing trend. For yield components, continuous drought stress significantly reduced spike length, effective number of spikes, thousand grain weight, grain number per spike, and fruiting rate of rice compared to CK treatments during the growth period. In general, continuous drought stress during the early growth period affected the effective spike number and the grain number per spike. Continuous drought stress after the grain filling stage had the least effect on yield and water use efficiency was much higher than other treatments. The results of these studies reveal the response of rice growth and physiology to continuous drought stress, which is important for agricultural practices.

This study investigated the impact of soil colloidal characteristics on the transfer patterns of different Cu and Cd speciation in contaminated soil treated with three different amendments: lime (L), zero-valent iron (ZVI), and attapulgite (ATP). It seeks to clarify the activation hazards and aging processes of these modifications on Cu and Cd. Compared with the control (CK), the available Cu concentrations treated with amendments reduced in the short term (6 months) by 96.49%, 5.54%, and 89.78%, respectively, and Cd declined by 55.43%, 32.31%, and 93.80%, respectively. Over a 12-year period, there was no significant change in the immobile effect with L, while Cu and Cd fell by 19.06% and 40.65% with ZVI and by 7.63% and 40.78% with ATP. Short- and long-term increases in the readily reducible iron and manganese oxide fraction of Cu and Cd were accompanied by a considerable rise in the concentrations of amorphous iron oxide in the soil and colloid after amendment treatment. This suggested that Cu and Cd were immobilized and stabilized in part by amorphous iron oxide.

To accurately evaluate the distribution and bioavailability of potentially toxic elements (PTEs) such as Cu and Cd in farmlands near a copper smelter, we determined the total concentrations (Cu-T and Cd-T), various speciation concentrations of Cu and Cd and physicochemical properties of 18 paddy soil (or colloid) samples in Guixi town, Jiangxi province, China. The results showed that the concentrations of Cu-T and Cd-T in the soil around the smelter far exceeded the standard limits. Specifically, Cu ranged from 97.47 to 1294.63 mg·kg⁻¹, with a coefficient of variation (CV) of 0.95; Cd ranged from 0.14 to 9.06 mg·kg⁻¹, and the CV was 1.68. Furthermore, the pollution of PTEs continued to accumulate, posing a significant risk to the environment and human health. The findings from the analysis of soil and colloid indicated that the distribution characteristics of Cu and Cd speciations did not align with the total concentrations. The highest pollution points were found to be shifted to the residual fraction of Cu, organic fraction, and crystalline iron oxide fraction of Cd in soil. The dominant fraction of Cu in colloid was the amorphous iron oxide fraction, whereas Cd was the crystalline iron oxide fraction. The assessment of Cu and Cd migration (M_R) revealed that Cd posed a greater ecological risk. Further examination of the properties of iron oxides in soil and colloid revealed that they played a crucial role in the migration and transformation of soil PTEs.

The aim of this study was to explore the differences in metabolites related to rice quality formation under different nitrogen (N) fertilizers and planting densities. In this study, Yangnongxiang 28 was used as the experimental material with the following conditions: high nitrogen and low density (HNLD; high nitrogen: 360 kg·hm⁻², low density: the row spacing of rice plants was 16 cm × 30 cm), medium nitrogen and medium density (MNMD; medium nitrogen: 270 kg·hm⁻², medium density: the row spacing of rice plants was 13 cm × 30 cm), and low nitrogen and high density (LNHD; low nitrogen: 270 kg·hm⁻², high density: the row spacing of rice plants was 10 cm × 30 cm). The rice quality indexes, including the processing quality, amylose content, and taste value, were compared under different treatments, and we analyzed their relationship with the metabolites. The results show that the milled rice rate of HNLD was 13.85% and was 1.89% higher than that of LNHD and MNMD, respectively. The head milled rice rate of HNLD was 32.45% and 6.39% higher than that of LNHD and MNMD, respectively. The milled rice rate and head milled rice rate of HNLD and MNMD were significantly higher than those of LNHD. This study identified 22 differential metabolites (DMs) in HNLD and LNHD, 38 DMs in HNLD and MNMD, and 23 DMs in LNHD and MNMD. Most of the identified differential metabolites were lipid metabolites, which were mainly enriched in the lipid metabolic pathways and amino acid metabolic pathways. The correlation analysis showed that the lipid metabolite physapubescin was significantly negatively correlated with the taste value. The lipid metabolites 2-undecen-1-ol, lucidenic acid F, and 8-deoxy-11,13-dihydroxygrosheimin were significantly positively correlated with the taste value. Lipids may be important substances that lead to differences in taste under different nitrogen fertilizer and density treatments.

We investigated the effects of reduced irrigation and N application, using green manure and rice straw, on the water‐use efficiency (WUE) and greenhouse gas (GHG) emissions of machine‐transplanted rice (Oryza sativa L.) to provide theoretical and technical guidance for water and N management in double‐cropping rice. Field trials were conducted from 2014 to 2016 using two irrigation methods (flood irrigation, W0; intermittent irrigation, W1) and three N application methods (no nitrogen application, N0; chemical nitrogen constant application, N1; chemical nitrogen reduction combined with green fertilizer and straw, N2). Methane (CH₄) and nitrous oxide (N₂O) emissions, water consumption, and grain yield were compared for the different treatment measures. Under the same N fertilizer management, intermittent irrigation reduced cumulative emissions of CH₄ of early and late season rice by 14.54–37.37% and 16.70–52.25%, respectively, whereas N₂O emissions increased by 12.50–35.29% and 23.08–34.09%, compared with flood irrigation. Under identical irrigation conditions, the cumulative CH₄ and N₂O emissions of early and late rice were N2 > N1 > N0. Compared to W0N1 treatment, W1N2 decreased the annual average water consumption by 4.40 and 5.53% for early and late rice, whereas yield and WUE increased by 4.27 and 3.98% and 9.54 and 9.71%, respectively. In addition, the annual global warming potential and greenhouse gas intensity of double‐cropped rice increased by 47.62 and 41.77%, respectively. The incorporation of green manure and rice straw with reduced N fertilizer application using intermittent irrigation in double rice cropping systems reduced water consumption and increased grain yield but also increased GHG emissions.

This study addresses the excessive consumption of river basin water from the Poyang Lake area in China. Consumption of water for irrigation, together with the discharge of agricultural non-point source pollution, is seriously affecting the water quality of Poyang Lake. This study assesses the application of integrated ecological restoration technology for agricultural non-point source pollution in the Ganfu Plain Area, which is an important agricultural production base in the Poyang Lake basin. The results indicated that the water-fertilizer comprehensive regulation mode for double-cropping rice provided water savings of 10.4% and increased rice yield by 6.5% per hectare. Furthermore, it reduced drainage water pollution by 20.4%, and emissions of ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), total phosphorus (TP), and total nitrogen (TN) from rice paddy surfaces by 18.6%, 11.1%, 15.4%, and 16.0%, respectively. The eco-channel–pond wetland system effectively reduced TN and TP pollutant levels in rice paddy drainage water; the eco-channel reduced TN and TP by 9.3% and 14.0%, respectively; and the pond wetland system showed reductions of 8.6% and 22.9%, respectively. The “three lines of defense” purification technology, including rice field source control, eco-channel interception, and pond wetland purification, removed 29.9% of TN and 44.3% of TP.