Sustainability assessment on paddy-upland crop rotations by carbon, nitrogen and water footprint integrated analysis: A field scale investigation

Spatio-temporal variations in carbon sources, sinks and footprints of cropland ecosystems in the Middle and Lower Yangtze River Plain of China, 2013-2022

Cropland ecosystems, which are most affected by human activities, are dual carriers of carbon sources and sinks. It has significant implications for the achievement of the "two-carbon" objective. The Middle and Lower Yangtze River Plain (MLYRP) is the principal grain-producing area of China, which is a great agricultural country. The development of green agriculture in this plain is of vital importance. Nevertheless, there is a lack of attention to the dynamics of the carbon footprints of cropland. Hence, this study was conducted with the help of carbon emission coefficient method. It investigated the spatio-temporal variations of carbon sources, sinks and carbon footprints of cropland ecosystems in this plain from 2013 to 2022. The findings suggest that (1) Carbon uptake was fluctuating up during the study period. Carbon uptake was higher in paddy and wheat. (2) Carbon emissions were declining year by year. Fertilizer and irrigated agriculture produced more carbon emissions. The top four for both indicators were Anhui, Jiangsu, Hubei and Hunan provinces. (3) The carbon footprint declined in fluctuations. This indicator ranked the top four in Hubei, Anhui, Zhejiang and Jiangsu provinces. The spatial distribution pattern of the above three indicators was more in the north and less in the south. (4) Cropland ecosystems exhibited carbon sinks. There were relatively large carbon eco-surplus and high carbon eco-efficiency. Nevertheless, the carbon ecological surplus was decreasing in fluctuation. Consequently, MLYRP should keep popularizing new technologies such as green manure crops and precision agriculture.

Sustainable food systems under environmental footprints: The delicate balance from farm to table

In today's world, agriculture is not only about food production but also a critical factor in global environmental change, economic stability, and human health, among other aspects. With population growth and increasingly scarce resources, exploring sustainable development of food systems has become crucial. Achieving this goal requires striking a delicate balance among food security, economic development, ecological environment, and human health. Traditional approaches to sustainable agricultural development research often focus solely on singular domains, overlooking the inherent connections and interactions among environmental, socioeconomic, and health dimensions. This perspective limits our comprehensive understanding of food systems. Environmental footprint assessments can be integrated with economic, systemic, and decision models to analyze environmental, socioeconomic, and health issues within food systems. This integration accurately captures the diversity, overlap, accumulation, and heterogeneity of environmental pressures resulting from human and natural factors. Therefore, we propose an innovative conceptual framework that considers environmental, socioeconomic, and health dimensions as crucial components, with the environmental footprint indicators at its core, to link various stages from farm to table. This framework constructs an evidence gap map, integrating dispersed data and perspectives from existing literature, thus showing knowledge gaps across these domains. Such an interdisciplinary approach not only provides a more comprehensive perspective on the multidimensional complexity of sustainable food systems but also reveals potential synergies and conflicts among environmental, socioeconomic, and health domains, thereby guiding more comprehensive and cautious policy-making. Importantly, it provides direction for future research to achieve the sustainable development of food systems, emphasizing the necessity of a comprehensive, integrated research perspective, particularly in strengthening studies on composited footprints, viewing the entire farm-to-table continuum holistically. Stakeholders must collaborate and coordinate environmental, socioeconomic, and health objectives to drive the sustainable development of food systems.

Green manure combined with reduced nitrogen reduce NH3 emissions, improves yield and nitrogen use efficiencies of rice

Background

Green manure is an important source of organic fertilizer. Exploring green fertilizer and nitrogen fertilizer reduction is important for agricultural production. However, few studies have been conducted, especially on the effects of different green fertilizers along with reduced nitrogen fertilizer application on soil ammonia volatilization emissions, rice yield, and nitrogen fertilizer uptake and utilization.

Methods

In this study, the effects of different types of green manure and reduced nitrogen fertilizer application on soil ammonia volatilization emissions, aboveground population characteristics of rice, and nitrogen fertilizer uptake and utilization were explored. This study was based on a field-positioning experiment conducted between 2020 and 2022. Six treatments were established: no nitrogen fertilizer application (CK), conventional fertilization in wheat-rice (WR), villous villosa-rice (VvR), vetch sativa-rice (VsR), rapeseed seed-rice (RR), and milk vetch-rice (GR), with a 20% reduction in nitrogen fertilizer application. The amounts of phosphorus and potassium fertilizers remained unchanged. The characteristics of ammonia volatilization loss in rice fields, agronomic traits of rice, yield traits, and nitrogen uptake and utilization were investigated.

Results

The results indicated a significant difference (P < 0.05) in the impact of different treatments on ammonia volatilization emissions from rice in the two-year experiment. Compared with WR treatment, VvR, VsR, RR, and GR treatments reduced the total ammonia volatilization loss by 23.58 to 39.21 kg ha-1, respectively. Compared with the conventional WR treatment, other treatments increased rice yield by 0.09 to 0.83 t ha-1. GR treatment was significantly higher than other green fertilizer treatments, except for VsR (P < 0.05). It increased the nitrogen uptake of rice by an average of 4.24%-22.24% and 13.08%-33.21% over the two years, respectively. The impact of different types of green manure on the nitrogen uptake and utilization of rice varied greatly, indicating that the combination of green manure and fertilizer is a sustainable fertilization model for crops to achieve high yields. In particular, the Chinese milk vetch as green manure was more beneficial for ammonia volatilization reduction in paddy field and stable grain production of rice.

Amendment of straw with decomposing inoculants benefits the ecosystem carbon budget and carbon footprint in a subtropical wheat cropping field

The incorporation of straw with decomposing inoculants into soils has been widely recommended to sustain agricultural productivity. However, comprehensive analyses assessing the effects of straw combined with decomposing inoculants on greenhouse gas (GHG) emissions, net primary production (NPP), the net ecosystem carbon budget (NECB), and the carbon footprint (CF) in farmland ecosystems are scant. Here, we carried out a 2-year field study in a wheat cropping system with six treatments: rice straw (S), a straw-decomposing Bacillus subtilis inoculant (K), a straw-decomposing Aspergillus oryzae inoculant (Q), a combination of straw and Bacillus subtilis inoculant (SK), a combination of straw and Aspergillus oryzae inoculant (SQ), and a control with no rice straw or decomposing inoculant (Control). We found that all the treatments resulted in a positive NECB ranging between 838 and 5065 kg C ha-1. Relative to the Control, the S treatment increased CO2 emissions by 16%, while considerably enhancing the NECB by 349%. This difference might be attributed to the straw C input and an increase in plant productivity (NPP, 30%). More importantly, in comparison to that in S, the NECB in SK and SQ significantly increased by 27-35% due to the positive response of NPP to the decomposing inoculants. Although the combination of straw and decomposing inoculants yielded a 3% increase in indirect GHG emissions, it also exhibited the lowest CF (0.18 kg CO2-eq kg-1 of grain). This result was attributed to the synergistic effects of straw and decomposing inoculants, which reduced direct N2O emissions and increased wheat productivity. Overall, the findings of the present study suggested that the combined amendment of straw and decomposing inoculants is an environmentally sustainable management practice in wheat cropping systems that can generate win-win scenarios through improvements in soil C stock, crop productivity, and GHG mitigation.

Dynamic simulation of the water-land-food nexus for the sustainable agricultural development in the North China Plain

Inter-regional trade of agricultural products based on the flow of agricultural virtual resources is of great importance for sustainable agricultural development. We focused on grain crops (rice, wheat and maize) in the North China Plain (NCP), and used the Penman-Monteith equation to simulate crop water requirements. We further analyzed the flow of virtual land and virtual water associated with the grain trade using an environmentally expanded multi-regional input-output model. The coupling coordination of land, water, and food was evaluated to assess the rationality of regional agricultural production resource allocation. Between 2007 and 2017, agricultural virtual land and virtual water embodied in the grain trade between the NCP and other areas increased by 48.10 % and 34.41 %, respectively, indicating that the NCP is gradually consolidating its position as the main production area and distribution center of crops in China. Agricultural virtual resources in the NCP were mainly transported to the southeast coastal region, with an overall trend of resource movement from north to south. The total supply of agricultural land and water resources markedly increased in the NCP, whereas the transfer of virtual resources across regions showed a decreasing trend. Because of the irrational structure of crop cultivation and unevenness of regional resource allocation, the coupling coordination of the water-land-food nexus in the NCP is much lower than the national average. This study provides important information on the trade flows and coupling relationships of virtual water and land resources of three major food crops, which will help to alleviate resource pressure in agricultural production and promote sustainable agricultural development in the NCP.

Balancing grain yield and environmental performance by optimizing planting patterns of rice-wheat cropping systems

To alleviate the adverse consequences of conventional planting of the rice-wheat cropping system and achieve long-term sustainability, a 3-cycle experiment (2019-2022) was conducted to investigate the effects of six planting patterns (PPs) on the grain yield and environmental performance. PP1 entailed annual rotary tillage (RT) without straw returning but without fertilization for rice and wheat seasons. PP2 was the same as PP1 but involved fertilization. PP3 was the same as PP2 but included straw return. PP4 entailed rice planting the same as in PP3, but with innovative zero-tillage (ZT) seeding technology for wheat planting. PP5 entailed wheat planting the same as in PP4, but with rice planting involving direct paddy seeding under RT. PP6 entailed wheat planting the same as in PP4, but rice planting followed dry direct seeding under ZT. The results showed that the average total yield under PP2, PP3, PP4, PP5, and PP6 was 64 %, 54 %, 69 %, 51 %, and 54 % higher than that under PP1, respectively. The highest methane and nitrous oxide emissions occurred under PP4 and PP6, respectively. When soil organic carbon changes were included in the calculations, the carbon footprint per unit area (CFA) was sharply reduced under PP4 and PP6, and the highest CFA was achieved under PP1, followed by PP2. Implementing annual RT promoted soil mineral nitrogen accumulation under PP2 and PP3 after wheat harvest, increasing the risk of mineral nitrogen leaching and the nitrogen footprint per unit area than that under the other PPs. PP4 exhibited the highest ammonia volatilization, which was offset by reduced mineral nitrogen leaching. Overall, PP4 exhibited a yearly increase in the comprehensive scores obtained via Z-score analysis and yielded the highest score in the last year due to the highest annual grain yield, steady SOC increase, and lower nitrogen loss.