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China’s agriculture is dominated by smallholder farms, which have become major sources of negative environmental impacts including eutrophication, formation of haze, soil acidification and greenhouse gas emissions. To mitigate these environmental impacts, new farming models including family farming, cooperation farming and industrial farming have emerged in recent years. However, whether these new farming practices would improve the economic and environmental performance as compared to the current smallholder farming has yet to be verified on ground level. In this paper, by using pilot farming cases within the watershed of Tai Lake, we found that alternative farming models produced 7% more crop yield, while using 8% less fertilizer, leading to a 28% decrease in pollutant emission per hectare. These alternative farming models have a 17% higher fertilizer use efficiency and 50% higher profit per hectare. Compared to smallholder farming, these alternative farming practices invest 27% more resources into agricultural facilities, including advanced machinery, and have a younger, better educated labor force as a consequence of a larger farm size and more specialization. These input changes substantially increase fertilizer use efficiency and reduce agricultural pollution. Policy arrangements to support and facilitate the uptake of these farming models will further promote the green development and sustainable intensification of agricultural production. Graphical abstract

In the Tailake region of China, heavy nitrogen (N) loss of rice-wheat rotation systems, due to high fertilizer-N input with low N use efficiency (NUE), was widely reported. To alleviate the detrimental impacts caused by N loss, it is necessary to improve the fertilizer management practices. Therefore, a 3 yr field experiments with different N managements including organic combined chemical N treatment (OCN, 390 kg N ha−1 yr−1, 20% organic fertilizer), control-released urea treatment (CRU, 390 kg N ha−1 yr−1, 70% resin-coated urea), reduced chemical N treatment (RCN, 390 kg N ha−1 yr−1, all common chemical fertilizer), and site-specific N management (SSNM, 333 kg N ha−1 yr−1, all common chemical fertilizer) were conducted in the Taihu Lake region with the 'farmer's N' treatment (FN, 510 kg N ha−1 yr−1, all common chemical fertilizer) as a control. Grain yield, plant N uptake (PNU), NUE, and N losses via runoff, leaching, and ammonia volatilization were assessed. In the rice season, the FN treatment had the highest N loss and lowest NUE, which can be attributed to an excessive rate of N application. Treatments of OCN and RCN with a 22% reduced N rate from FN had no significant effect on PNU nor the yield of rice in the 3 yr; however, the NUE was improved and N loss was reduced 20-32%. OCN treatment achieved the highest yield, while SSNM has the lowest N loss and highest NUE due to the lowest N rate. In wheat season, N loss decreased about 28-48% with the continuous reduction of N input, but the yield also declined, with the exception of OCN treatment. N loss through runoff, leaching and ammonia volatilization was positively correlated with the N input rate. When compared with the pure chemical fertilizer treatment of RCN under the same N input, OCN treatment has better NUE, better yield, and lower N loss. 70% of the urea replaced with resin-coated urea had no significant effect on yield and NUE improvement, but decreased the ammonia volatilization loss. Soil total N and organic matter content showed a decrease after three continuous cropping years with inorganic fertilizer application alone, but there was an increase with the OCN treatment. N balance analysis showed a N surplus for FN treatment and a balanced N budget for OCN treatment. To reduce the environmental impact and maintain a high crop production, proper N reduction together with organic amendments could be sustainable in the rice-wheat rotation system in the Taihu Lake region for a long run.

Non-point source (NPS) pollution has been increasingly serious in China since the 1990s. The increases of agricultural NPS pollution in China is evaluated for the period 2000−2008 by surveying the literature on water and soil pollution from fertilizers and pesticides, and assessing the surplus nitrogen balance within provinces. The main causes for NPS pollution were excessive inputs of nitrogen fertilizer and pesticides, which were partly the result of the inadequate agricultural extension services and the rapid expansion of intensive livestock production with little of waste management. The annual application of synthetic nitrogen fertilizers and pesticides in China increased by 50.7 and 119.7%, respectively, during 1991−2008. The mitigation measures to reduce NPS pollution include: correct distortion in fertilizer prices; improve incentives for the recycling of organic manure; provide farmers with better information on the sound use of agro-chemicals; and tighten the regulations and national standards on organic waste disposal and pesticides use.

Under today’s climate warming, mitigating the risks of soil organic carbon (SOC) decomposition in cropping systems is critical to maintain carbon sequestration. This study posits that nitrogen addition rate and duration are the key factors influencing the responses of soil heterotrophic respiration (Rh) to climate warming in a cropping system. Based on soil sampled from traditional-agriculture rice-growing regions in the Taihu Lake Basin in eastern China, this study aimed to clarify how nitrogen addition strategies affect soil Rh and its temperature sensitivity (Q10) and to explore the underlying mechanisms of the changes in soil environment that influence carbon emissions under nitrogen addition through the Rh pathway. The results demonstrate that, with the increasing duration of nitrogen addition, soil Rh and its Q10 were initially increased but subsequently suppressed, and the inhibitory effect on soil Rh became apparent after six years of continuous addition. Further analysis revealed that decreases in C/N, pH, and extractable organic nitrogen and increases in mineral nitrogen are the primary factors suppressing soil Rh. These findings indicate that an optimized nitrogen addition strategy tailored to specific crops could achieve profitable crop yields while effectively mitigating the promoting effect of climate warming on SOC decomposition.

Intensive irrigated rice-wheat crop systems have caused serious soil depletion and nitrogen loss in the Tai Lake region of China. A possible solution is the incorporation of legumes in rice because legumes are a source of nitrogen. There is actually little knowledge on the impact of legumes on rotation, soil fertility, and nitrogen loss. Therefore, we studied the effect of five rice-based rotations, including rice-wheat, rice-rape, rice-fallow, rice-bean, and rice-vetch, on soil nitrogen, rice yield, and runoff loss. A field experiment was conducted in the Tai Lake region from 2009 to 2012. Crop residues from rape, bean, and vetch were used to partially replace chemical fertilizer in rice. Results show that replacing 9.5–21.4 % of mineral nitrogen fertilizer by residues maintained rice yields of rice-rape, rice-bean, and rice-vetch rotations, compared to the rice-wheat reference. Moreover, using legumes as a winter crop in rice-bean and rice-vetch combinations increased rice grain yield over 5 %, and increased rice residue nitrogen content by 9.7–20.5 %. Nitrogen runoff decreased 30–60 % in rice-rape, rice-bean, and rice-vetch compared with rice-wheat. Soil mineral nitrogen and microbial biomass nitrogen content were also improved by application of leguminous residues.

Agricultural non-point source pollution has emerged as a significant driver of declining global water quality in recent years. Ditch systems hold considerable promise for trapping and purifying pollutants. However, the persistent challenge has been the limited availability of carbon sources in drainage water, which significantly hinders nitrogen (N) removal in ditches. This study investigated the dynamic changes in ammonia (NH4+) and nitrate (NO3−) levels caused by three cellulosic carbon additions (rice straw, coir, and sawdust) during both winter and summer seasons. Water column devices were used as containers, and the impacts on environmental factors and water denitrification rates were explored. Results demonstrated that the addition of straw exhibited the most effective N removal in winter and summer, and significantly enhanced water denitrification rates in a short timeframe, with the maximum denitrification rate reaching 1482.42 μmol·L−1·h−1. However, there was an observed accumulation of NH4-N and chemical oxygen demand (COD) in summer. Also, the addition of sawdust resulted in a notable increase in greenhouse gas emissions during the summer test. In conclusion, during the cooler seasons of winter and spring when temperatures are not as high, the combined use of various cellulosic carbon sources has the potential to enhance water denitrification and mitigate adverse environmental impacts, offering valuable applications for water quality improvement.

To assess the effect of long-term fertilization on labile organic matter fractions, we analyzed the C and N mineralization and C and N content in soil, particulate organic matter (POM), light fraction organic matter (LFOM), and microbial biomass. Results showed that fertilizer N decreased or did not affect the C and N amounts in soil fractions, except N mineralization and soil total N. The C and N amounts in soil and its fractions increased with the application of fertilizer PK and rice straw. Generally, there was no significant difference between fertilizer PK and rice straw. Furthermore, application of manure was most effective in maintaining soil organic matter and labile organic matter fractions. Soils treated with manure alone had the highest microbial biomass C and C and N mineralization. A significant correlation was observed between the C content and N content in soil, POM, LFOM, microbial biomass, or the readily mineralized organic matter. The amounts of POM-N, LFOM-N, POM-C, and LFOM-C closely correlated with soil organic C or total N content. Microbial biomass N was closely related to the amounts of POM-N, LFOM-N, POM-C, and LFOM-C, while microbial biomass C was closely related to the amounts of POM-N, POM-C, and soil total N. These results suggested that microbial biomass C and N closely correlated with POM rather than SOM. Carbon mineralization was closely related to the amounts of POM-N, POM-C, microbial biomass C, and soil organic C, but no significant correlation was detected between N mineralization with C or N amounts in soil and its fractions.

The development of biochar-based granule-like adsorbents suitable for scaled-up application has been attracting increasing attention in the field of water treatment. Herein, a new formable porous granulated biochar loaded with La-Fe(hydr)oxides/montmorillonite (LaFe/MB) was fabricated via a granulation and pyrolysis process for enhanced phosphorus (P) removal from wastewater. Montmorillonite acted as a binder that increased the size of the granulated biochar, while the use of Fe promoted the surface charge and facilitated the dispersion of La, which was responsible for selective phosphate removal. LaFe/MB exhibited rapid phosphate adsorption kinetics and a high maximum adsorption capacity (Langmuir model, 52.12 mg P g−1), which were better than those of many existing granulated materials. The desorption and recyclability experiments showed that LaFe/MB could be regenerated, and maintained 76.7% of its initial phosphate adsorption capacity after four adsorption cycles. The high hydraulic endurance strength retention rate of the developed material (91.6%) suggested high practical applicability in actual wastewater. Electrostatic attraction, surface precipitation, and inner-sphere complexation via ligand exchange were found to be involved in selective P removal over a wide pH range of 3–9. The thermodynamic parameters were determined, which revealed the feasibility and spontaneity of adsorption. Based on approximate site energy distribution analyses, high distribution frequency contributed to efficient P removal. The research results provide a new insight that LaFe/MB shows great application prospects for advanced phosphate removal from wastewater.Graphical AbstractNovel formable porous functional biochar (LaFe/MB) was prepared for P removal.La/Fe oxide provides abundant sorption sites for P and almost no La/Fe leaching.LaFe/MB presented high compressive strength with high sorption capacity for P.

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.

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.