Effects of multi-cropping system on temporal and spatial distribution of carbon and nitrogen footprint of major crops in China

Sustainable crop production: Highlights on economic, environmental and social life cycle thinking

Seeking multi-dimensional inclusion is one of the most global concerns of the crop production sector worldwide. Socio-eco-effectiveness or socio-eco-efficiency optimization plays a crucial role in future strategy establishment. Life cycle is a widely used approach examining economic, environmental, and social impacts. Recently, life cycle thinking approaches have been increasingly utilized to bring to light useful perceptions of the crop production processes. This study aims to apply a systematic review and prescriptive analytics to critically investigate the life cycle thinking approaches application according to sustainability pyramid aspects, life cycle thinking unicity, goal and scope variability, functional units' causality, system boundary' diversity, involved aspect' concentration, indicators, impacts categories and influencing variables distribution, as well as to define a first datasheet model and directive axis to apply per aspect and family for socio-eco-effectiveness or socio-eco-efficiency evaluation. Over 295 peer-reviewed studies from 2019 to the middle of 2023, 52 reviews and articles gathered from Web of Science and Scopus meet the criteria to be analyzed. Our inspection revealed that related reviews are few, approximately 2 %. Moving from the traditional life cycle perspective to the sustainability pyramid approach, the indicators applied by researchers were classified per aspect and family belonging. A deductive analysis was carried out to narrow the impact categories, and the influencing factors to the population's main interests: four economic (input status, resources consumption, waste, and Costs of Life Cycle), eight environmental (Climate Change, Global Warming, Ozone, Acidification, Eutrophication, Photochemical Oxidation, Abiotic Depletion, and Toxicity), and three social families (Human Toxicity, employment, and Ionizing Radiation). The results combination highlights the construction need for a directive datasheet model to address the optimizing problem under the identified families and aspects constraints, as well as to envisage the units and methods worldwide standardization's necessity for spatial-temporal studies comparison in the present, the past, and the future.

Reducing the environmental impact of rice production in subtropical India by minimising reactive nitrogen loss

The future of reactive nitrogen (N) for subtropical lowland rice to be characterised under diverse N-management to develop adequate sustainable practices. It is a challenge to increase the efficiency of N use in lowland rice, as N can be lost in various ways, e.g., through nitrous oxide (N2O) or dinitrogen (N2) emissions, ammonia (NH3) volatilization and nitrate (NO3-) leaching. A field study was carried out in the subsequent wet (2021) and dry (2022) seasons to assess the impacts of different N management strategies on yield, N use efficiency and different N losses in a double-cropped rice system. Seven different N-management practices including application of chemical fertilisers, liquid organic fertiliser, nitrification inhibitors, organic nutrient management and integrated nutrient management (INM) were studied. The application of soil test-based neem-coated urea (NCU) during the wet season resulted in the highest economic yield, while integrated nutrient management showed the highest economic yield during the dry season. Total N losses by volatilization of NH3, N2O loss and leaching were 0.06-4.73, 0.32-2.14 and 0.25-1.93 kg ha-1, corresponding to 0.06-5.84%, 0.11-2.20% and 0.09-1.81% of total applied N, respectively. The total N-uptake in grain and straw was highest in INM (87-89% over control) followed by the soil test-based NCU (77-82% over control). In comparison, recovery efficiency of N was maximum from application of NCU + dicyandiamide during both the seasons. The N footprint of paddy rice ranged 0.46-2.01 kg N-eq. t-1 during both seasons under various N management. Ammonia volatilization was the process responsible for the largest N loss, followed by N2O emissions, and NO3- leaching in these subtropical lowland rice fields. After ranking the different N management practices on a scale of 1-7, soil test-based NCU was considered the best N management approach in the wet year 2021, while INM scored the best in the dry year 2022.

Incorporating carbon sequestration toward a water-energy-food-carbon planning with uncertainties

Water-energy-food nexus (WEFN) is the core content in the United Nations 2030 Agenda for Sustainable Development. However, the value of soil and crops' carbon sink function has not yet been fully considered in the managment practices of WEFN system. Here, we developed a water-energy-food-carbon nexus (WEFCN) planning framework that incorporates carbon sequestration and multiple mathematical optimization methods into the practical WEFN management for Henan Province, which is one of major grain-producing areas in China. Uncertainties from multiple objectives, scenarios, and different stakeholder interests are captured. We found that wheat has the largest carbon sequestration, followed by corn and oil-bearing crops, while other crops have implicit carbon sequestration. Since chemical fertilizer produces the most carbon emissions, the usage of chemical fertilizer needs to be reasonably controlled. Overall, the proposed framework supports optimal decision-making for regional-scale WEFCN management and further unlocks the hidden value of agricultural carbon mitigation.

Reactive nitrogen releases and nitrogen footprint during intensive vegetable production affected by partial human manure substitution

Evaluating the sustainability of vegetable production is crucial to secure future food supply. A 2-year field study of four different vegetable crops was performed to investigate the effects of inorganic fertilizer and human manure at different ratios on vegetable yields, reactive gaseous nitrogen emissions (GNrEs), reactive nitrogen (Nr) footprint, and net ecosystem economic income (NEEI) by using life cycle analysis. Four fertilization strategies were studied, including CK (no fertilization); CF (inorganic fertilization); CHF1 (human manure /inorganic fertilizer, N ratio = 1:7); and CHF2 (human manure /inorganic fertilizer, N ratio = 1:3). Results showed that compared with CF treatment, both CHF1 and CHF2 treatments increased the N₂O + NO emissions by 11.8% and 32.4% on average, while decreased the vegetable yields by 6.7% and 7.4%, respectively. Moreover, the addition of human manure increased the proportions of Nr footprint by 6.6% (CHF1) and 2.9% (CHF2) in comparison with CF treatment. However, although CHF2 treatment significantly increased the values of GNrEs and reactive gaseous nitrogen intensity (GNrI) by 8.4% and 12.5%, respectively, in relation to those in CF treatment, it still increased farmers' income by 16,404 CNY ha^-1. These findings suggest that although human manure incorporation could not mitigate Nr releases, the appropriate ratio of inorganic fertilizer and human manure (CHF2) is able to improve net economic income (NEI) and NEEI during intensive vegetable production. Nevertheless, it should be further explored about the relationship between combinatorial treatment of inorganic fertilizer and human manure on Nr release mitigation in intensive vegetable production.

Greenhouse gas emissions and mitigation potential of hybrid maize seed production in northwestern China

Although hybrid maize seed production is one of the most important agriculture systems worldwide, its greenhouse gas (GHG) emissions and potential mitigation measures have not been studied. In this study, we used life cycle assessment (LCA) to quantify the GHG emissions of 150 farmers run by 6 companies in an area of northwest China known for hybrid maize seed production. The results indicated that the average reactive nitrogen (Nr) losses and GHG emissions from hybrid maize seed production were 53 kg N ha^-1 and 8077 kg CO₂ eq ha^-1, respectively. Furthermore, the average nitrogen and carbon footprints of the process were 12.2 kg N Mg^-1 and 1495 kg CO₂ eq Mg^-1, respectively. Nitrogen fertilizer and electricity consumption for irrigation were the main contributors to high GHG emissions, accounting for 60% and 30% of the total, respectively. The GHG emissions from seed production for different companies varied greatly with their resource input. There was also a large variation in environmental burdens among the 150 farmers. Based on an analysis of the yield group, we found that the carbon footprint of the first group (the one with the highest yield) was 27% lower than the overall average. Scenario analysis suggests that a combined reduction of N input rate, optimizing irrigation, and increasing yield can eventually mitigate the carbon footprint of hybrid maize seed production by 37%. An integrated systematic approach (e.g., ISSM: integrated soil-crop system management) can reduce the GHG emissions involved in producing hybrid maize seeds. This study provides quantitative evidence and a potential strategy for GHG emissions reduction of hybrid maize seed production.

Indicators and Recommendations for Assessing Sustainable Healthy Diets

Research coupling human nutrition and sustainability concerns is a rapidly developing field, which is essential to guide governments' policies. This critical and comprehensive review analyzes indicators and approaches to "sustainable healthy diets" published in the literature since this discipline's emergence a few years ago, identifying robust gauges and highlighting the flaws of the most commonly used models. The reviewed studies largely focus on one or two domains such as greenhouse gas emissions or water use, while overlooking potential impact shifts to other sectors or resources. The present study covers a comprehensive set of indicators from the health, environmental and socio-economic viewpoints. This assessment concludes that in order to identify the best food option in sustainability assessments and nutrition analysis of diets, some aspects such as the classification and disaggregation of food groups, the impacts of the rates of local food consumption and seasonality, preservation methods, agrobiodiversity and organic food and different production systems, together with consequences for low-income countries, require further analysis and consideration.

Drivers of the Growing Water, Carbon and Ecological Footprints of the Chinese Diet from 1961 to 2017

In the past decades, food consumption in China has undergone a rapid increase and a significant structure transition, as a result of population growth and economic development. The food system is increasingly threatening the environment by depleting water resources, deteriorating water bodies, aggravating climate change, degrading ecosystems, etc. It is significant to understand how food consumption affected the environment and how its impacts were driven in the historical period. This study reveals the environmental impacts of China's food system from 1961 to 2017 from a consumption perspective by assessing water, carbon, and ecological footprints. The logarithmic mean Divisia index method was used to examine the drivers of the growing environmental footprints. The assessment results show that all three environmental footprints have had a drastic increase of more than two times during the studied period, which indicates the high environmental pressure posed by food consumption. We also found that, before the 1980s, the main driving forces of the increasing footprints were population and per capita energy intake. From 1984, the diet pattern started to take a positive effect and then became the dominant driver of the growing environmental footprints after the end of the 1990s.