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Long-term large inputs of phosphorus (P) fertilizer in China have caused serious soil P accumulation, low P use efficiency (PUE) and high risk of P loss. Controlling the amount of P fertilizer applied presents an inevitable choice for improving the PUE. Struvite recycled from agricultural wastewater rich in N and P concentrations are capable of slow nutrient release, improving nutrient uptake and enabling the reuse of nutrients from environmental sources when applied to agricultural land. A two-year field experiment was conducted to investigate the effects of struvite combined with P reduction under a rice–wheat rotation system in eastern China. A total of five treatments were set up, including conventional fertilization (FP), a struvite substitution of 100% P fertilizer (SP), a 50% P reduction with struvite substitution (RSP), no application of N fertilizer (N0) and no application of P fertilizer (P0). Grain yield, crop N and P uptake, N and P use efficiency (NUE and PUE) and soil nutrient status were assessed. Under the same P application rate, the yield and aboveground biomass of the SP treatment were slightly higher than those of FP treatment, but the crop P uptake, PUE and soil available P content were significantly increased. The RSP treatment did not reduce yield with 50% P reduction, and significantly improved the PUE and soil available P content. Crop N uptake and NUE were also found to be increased in SP and RSP treatments with struvite substitution. The P apparent balance showed that both the SP and FP treatments had a P surplus, but the RSP treatment had a P break-even, and the soil available P content remains stable compared with the initial value. The results indicate that struvite application could improve the soil P availability and crop nutrient uptake then promote the crop yield. To increase the nutrient use efficiency of crops while ensuring crop yield and soil fertility, appropriate P reduction combined with struvite as a P fertilizer could be sustainable in the rice–wheat rotation system in the long run.

One-time application of controlled-release blended fertilizer (CRBF, a mixture of five nitrogen (N) fertilizers in a certain ratio) can achieve high yield and N use efficiency (NUE) in rice (Oryza sativa L.). However, the effects of CRBF with one-time application on root spatial distribution and physiological characteristics remain unclear. We measured the effects of CRBF with one-time application on rice yield, NUE, root morphology and growth, and N uptake capacity in field and root box experiments. Six N treatments were set up: no nitrogen (N0), high-yield three-split application of urea as a control (CK), urea (U) with broadcast, U with side-deep fertilization, CRBF with broadcast, and CRBF with side-deep fertilization. Our findings showed that root characters were positively correlated with yield and NUE. Compared to CK and U treatments, CRBF with one-time applications increased root characters (including root biomass, root N uptake, root activity, and the expression level of ammonium transporters) at tillering and heading stages. The root length, surface area and volume in the 0–10 cm soil layer enhanced under CRBF with one-time applications at tillering stage, and in the 0–20 cm soil layer at the heading stage. This contributed a 5.96%–39.40% and 3.69%–16.87% increase in plant dry matter accumulation and N uptake, and a 2.08%–18.28% and 14.60%–149.57% increase in yield and NUE, in 2022 and 2023, respectively. Taken together, our findings showed that one-time application of CRBF could increase rice yield and NUE by optimizing the root morphology distribution and N uptake.

Clarifying the benefits of carbon sequestration and crop production of continuous green manure amendment is crucial for sustainable agricultural development. Here, using a long-term located experiment, we assessed the effects of 18 years’ ryegrass/milk vetch amendment with (NF, 150 kg N ha−1) or without nitrogen (N) fertilizer input (CK), on soil carbon management indices, paddy methane (CH4) emissions and rice yields. The results showed that green manure, rather than fertilization, played a critical role in soil CMI, increasing the carbon pool index but reducing the carbon management index. The increased soil organic carbon and the reduced labile organic carbon were the main causes for this performance. Additionally, the effects of both fertilization and green manure amendment on CH4 emissions were insignificant; however, fertilization significantly increased grain yield by 39.30% compared to CK. As a result, the methane emission intensity under fertilization treatment was notably lower than that from CK. The findings suggest that green manure amendment is a profitable manipulation for enhancing carbon sequestration without increasing paddy CH4 emissions. However, this cannot substitute the critical role of N fertilizer in rice production.

What strategy of nutrient management can maintain the high and stable annual yield in rice–wheat systems under climate change? A 10-year term experiment was conducted in the rice–wheat system to investigate the effect of optimal nutrient management on crop yield and meteorological drivers of year-to-year fluctuations in rice and wheat yield. Treatments were as follows: conventional fertilization (CF, as control), fertilizer postponing (FP, with the same amount fertilization as CF and increasing rate and times of panicle fertilizer) with/without straw incorporation (including only straw returned in rice (W) or wheat (R) season, and both straw incorporation (WS), RFP (reducing amount based on FP) with/without organic fertilizer. Results showed that FP with/without straw incorporation increased 10-year average yields of rice, wheat, and annual by 4.5~6.5%, 3.8~7.2%, and 4.8~6.8%, respectively, while RFP with/without organic fertilizer did not markedly reduce wheat yield, compared with CF. Effect of optimal treatments on wheat and rice yield stability was different; among the annual yield stability in FP + WRS was the greatest due to increasing and a stable number of spikelets and dry matter accumulation (DMA) after heading. Furthermore, the coefficient of variation (CV) of DMA during rice jointing-heading (21.6~30.0%) and heading-maturity stage (20.1~27.9%) was higher than before jointing (13.9~16.7%), which were affected by day photosynthetically active radiation (explain: 26%) and the number of rainy days (explain: 34%), respectively, using Stepwise regression; in contrast, in wheat season, the fluctuation of DMA before jointing was the highest (CV: 83.8~109.9% (before jointing) vs. 61.1~97.4% (heading-mature stage) vs. 33.7~46.3% (jointing-heading period), 55% of its variations was impacted by day-night temperature differences, the number of rainy days and photosynthetically active radiation accumulation. Our finding suggested that nutrient management to increase and stable the DMA after rice jointing and before wheat jointing could maintain the high and stable annual yield in rice–wheat systems.

Constructed wetlands (CWs) are effective wastewater treatment systems, relying on plant and substrate uptake and microbial depletion to remove pollutants. It has been reported that melatonin can promote plant growth and change the structure of microbial communities. The effects of melatonin on stress tolerance of plants have been extensively studied, while the effects of melatonin on the efficiency of wastewater treatment in constructed wetlands are rarely known. In the current study, 1 mM melatonin was added to the constructed wetland systems to determine physiological characteristics of Phragmites australis, microbial enzyme activity, and microbial community structure of CWs. Under melatonin treatment, the An and gs of Phragmites australis plants were significantly improved compared with the control. In addition, the contents of phosphate and total anion in the xylem sap of Phragmites australis significantly increased. However, the concentration of total phosphorus in the effluent did change significantly. Melatonin treatment improved the dehydrogenase activity and significantly improved the removal efficiency of NH4+-N in CWs. Furthermore, melatonin reduced the richness of the microbial community in CWs, while it increased the diversity of bacterial community and altered microbial composition. FARPROTAX analysis showed that melatonin increased the abundance of bacteria involved in nitrogen fixation and ureolysis, which may be related to the improvement of plant photosynthetic performance and improved rhizosphere oxygen environment. These results suggested that melatonin may affect plant performance and microbial composition and functions to improve the purification effect of constructed wetland.

Belowground fertilization is a prevalent strategy for considerable grain yield and N utilization. However, the optimal fertilization depth remains uncertain in paddies, especially for slow/controlled release fertilizers. This study aimed to clarify the effect of deep “controlled‐release blended fertilizer” (CRBF) fertilization on rice (Oryza sativa L.) yield and N utilization. Two N‐fertilizer types were selected (a) urea and (b) CRBF, both combined at three fertilization depths (a) 0 cm, (b) 5 cm, and (c) 10 cm. The results showed that the grain yield was significantly affected by fertilizer type and fertilization depth. The yield achieved from CRBF was 7.8% higher than that from the urea application. Deep fertilization could also increase the rice yield with the optimum achieved from the 5‐cm depth fertilization (yield increased by 15.1% compared to that from the manual surface fertilization). Overall, the 5‐cm depth CRBF fertilization achieved the highest yield among all treatments with 12.21 and 11.84 t ha–1 for 2018 and 2019, respectively. The larger sink was the main reason for this performance. Additionally, the higher photosynthetic efficient population after earing was another principal driver to the higher yield from CRBF. Due to the higher N uptake, CRBF application increased both N partial factor productivity (PFP) and recovery efficiency (RE) (P < .05); fertilization depth also had a striking effect on PFP and RE (P < .05 or .01). The 5‐cm depth fertilization of CRBF achieved the highest N utilization for both years. The results suggest that 5‐cm depth fertilization combined with controlled‐release fertilizer is a suitable strategy for higher rice yield and N utilization. Core Ideas The grain yield from CRBF was higher than that from the urea application treatments. Deep fertilization proved to be a strategy able to increase rice yield. The CRBF fertilization at a 5‐cm depth could achieve the optimum yield. For the yields achieved, CRBF fertilization at 5‐cm depth achieved the highest N utilization.

Introduction: This study aimed to assess the influence of experimental warming and fertilization on rice yield and paddy methane emissions. Methods: A free-air temperature increase system was used for the experimental warming treatment (ET), while the control treatment used ambient temperature (AC). Each treatment contained two fertilization strategies, (i) normal fertilization with N, P and K fertilizers (CN) and (ii) without N fertilizer input (CK). Results: The yield was remarkably dictated by fertilization (p < 0.01), but not warming. Its value with CN treatment increased by 76.24% compared to CK. Also, the interactive effect of warming and fertilization on CH4 emissions was insignificant. The seasonal emissions from warming increased by 36.93% compared to AC, while the values under CN treatment increased by 79.92% compared to CK. Accordingly, the ET-CN treatment obtained the highest CH4 emissions (178.08 kg ha−1), notably higher than the other treatments. Also, the results showed that soil fertility is the main driver affecting CH4 emissions rather than soil microorganisms. Conclusions: Fertilization aggravates the increasing effect of warming on paddy methane emissions. It is a daunting task to optimize fertilization to ensure yield and reduce methane emissions amid global warming.

Core Ideas CSRF application (RBBbasal, RBBBP, SCUBP) increased the NUE in both seedling‐transplanted and direct‐seeded fields. Yield increase of resin‐blending controlled‐release fertilizer was better than that of sulfur‐coated fertilizer under the two planting modes. “Base‐panicle” fertilization with RBB and urea was suitable for the seedling‐transplanted mode. A single basal application of RBB was suitable for direct‐seeded mode for achieving the high yield. To understand the response of rice yield and N utilization to controlled or slow‐release fertilizers (CSRFs) under direct‐seeded or seedling‐transplanted modes of rice production, a field experiment with rice variety Wuyunjing 23 was performed in 2013 and 2014. Five treatments, including two CSRFs: sulfur‐coated urea (SCU) and resin‐blending controlled‐release fertilizer (RBB), two fertilization modes: single basal application and a split “base‐panicle” (BP) application, and conventional split fertilization (CONV) as a control, were conducted. The results showed that there was no improvement of yield for SCU application compared with CONV in the seedling‐transplanted and direct‐seeded modes in both years. The yield increasing effect of RBB was better than that of SCU under the two planting modes. The interaction effect between the planting mode and fertilizer treatment on the yield was significant. The yield of RBBBP treatment was the highest in seedling‐transplanted fields, reaching 12.04 t ha−1 in 2013 and 13.44 t ha−1 in 2014. By contrast, the yield of RBBbasal treatment was the highest in direct‐seeded rice, although the difference among the treatments was not significant. The CSRF application (RBBbasal, RBBBP, SCUBP) increased the NUE in both the seedling‐transplanted and direct‐seeded fields. Except for the NUE of RBBbasal, which was the highest for direct‐seeded rice in 2013, the RBBBP treatment showed the highest NUE in seedling‐transplanted and direct‐seeded rice in both years. The results indicated that RBB increased the yield and NUE in both seedling‐transplanted and direct‐seeded modes, and the combined panicle urea and RBB was better in seedling‐transplanted fields, while a single basal application with RBB was better in direct‐seeded rice.

Introduction: This study aimed to assess the influence of experimental warming and fertilization on rice yield and paddy methane emissions. Methods: A free-air temperature increase system was used for the experimental warming treatment (ET), while the control treatment used ambient temperature (AC). Each treatment contained two fertilization strategies, (i) normal fertilization with N, P and K fertilizers (CN) and (ii) without N fertilizer input (CK). Results: The yield was remarkably dictated by fertilization (p < 0.01), but not warming. Its value with CN treatment increased by 76.24% compared to CK. Also, the interactive effect of warming and fertilization on CH[sub.4] emissions was insignificant. The seasonal emissions from warming increased by 36.93% compared to AC, while the values under CN treatment increased by 79.92% compared to CK. Accordingly, the ET-CN treatment obtained the highest CH[sub.4] emissions (178.08 kg ha[sup.−1]), notably higher than the other treatments. Also, the results showed that soil fertility is the main driver affecting CH[sub.4] emissions rather than soil microorganisms. Conclusions: Fertilization aggravates the increasing effect of warming on paddy methane emissions. It is a daunting task to optimize fertilization to ensure yield and reduce methane emissions amid global warming.

Background Limiting warming-induced increases in paddy NH 3 volatilization (NV) and greenhouse gas (GHG) emissions is critical. While hydrochar reduce both, its efficacy under warming remains unclear. Results To address this gap, an in-situ microcosm column experiment was employed to examine the impact of hydrochar addition on NV and GHG emissions from paddies under experimental warming (ET, 1.1 ~ 1.3 °C) and ambient control (AC), with (WHC) and without hydrochar (CKU). Results showed no significant interactive effects between warming and hydrochar on cumulative NV, seasonal CH 4 and N 2 O emissions. Compared to AC, ET treatments unsurprisingly increased NV and GHG emissions, with significant differences in NV and CH 4 emissions. Fortunately, WHC treatment not only reduced CH 4 emissions under both temperature conditions but also tended to decrease N 2 O emissions under warming conditions. Notably, under ambient control conditions, WHC treatment reduced NV by 29.60% compared to CKU, whereas, under warming conditions, NV losses were comparable between the two treatments. Moreover, N concentration and soil physicochemical properties (pH, carbon and nitrogen contents) were identified as the primary factors determining NV and CH 4 emissions, respectively, whilst N 2 O emissions were influenced by soil pH, dissolved organic carbon, and microbial ( nir K and AOA genes). Conclusions Overall, hydrochar can mitigate warming-induced paddy GHG emissions but not the increase in NV, which warrants attention. Graphical abstract