Phosphorus flow analysis in the maize based food-feed-energy systems in China.

Phosphorus (P) is an essential and limiting nutrient for agricultural systems, where the demand for agricultural products such as food, feed, and bio-fuel are the major drivers of the intensification of agricultural production systems. Globally, maize is one of three main cereal crops, a main feedstock for animal production and a substrate for the production of bio-ethanol. This study investigated P flows through the multiple utilization systems of maize (as represented by the subsystems of food, feed and energy production) at a crop level of 2016 as reference year and made future predictions of P flows for the year 2030 based on different scenarios for food-feed-energy systems in China. For 2016, the subsystem of animal production resulted in the highest waste of P due to inappropriate manure management, but the subsystem of value-added products (Bio-fuel production, distillers dried grains with solubles (DDGS), maize-oil) showed the lowest P use efficiency (39%). From the value-added subsystem, 17% of P from the process flow to the subsystem of animal production as DDGS, and 61% of P is wasted associated with wastewater and sludge. Future scenarios of structural adjustments in the maize consumption system predict that the supply of maize for animal feed will be threatened if the policy of the Biofuel National Promotion before 2020 is fully implemented in China, as current maize production will not meet the future demand of food, feed and energy simultaneously. The results emphasized the use of P waste resources and better sludge management from a systems perspective. This also implied the importance of exploring coordinated development and integrated strategies for sustainable P flow management in multiple utilization systems.

Using knowledge-based management for sustainable phosphorus use in China.

Sustainable phosphorus (P) management presents challenges in crop production and environmental protection; the current understanding of chemical P-fertilizer manufacturing, rock phosphate (RP) mining, P loss within supply chains, and strategies to mitigate loss is incomplete because of a fragmented understanding of P in the crop production supply chain. Therefore, we develop a knowledge-based management theoretical framework to analyze P supply chains to explore ways to mitigate China's P crisis. This framework connects upstream P industries and crop production, addressing knowledge gaps and stakeholder involvement. We demonstrate the potential to improve P use efficiency in the supply chain, thereby mitigating the P crisis using optimized P management. Our results showed that P footprint and grain production demand for RP can be reduced without yield penalty using a crop-demand-oriented P supply chain management that integrates P use in crop production, P-fertilizer manufacturing, and RP mining. Food security and P-related environment sustainability can be achieved by sharing responsibility and knowledge among stakeholders.

International trade reduces global phosphorus demand but intensifies the imbalance in local consumption.

International trade has led to increasing levels of economic development; however, its role in altering the global phosphorus (P) demand and local P footprint (PF) is unclear. Here, through a multi-regional input-output (MRIO) analysis, we quantified the PF associated with the global consumption of agricultural products for 159 countries and 169 crops over the period of 1995-2015. The results suggested that the international network of P flows was highly connected and the flow distribution was overridingly driven by developed economies (e.g., USA and Germany) and large emerging economies (e.g., China and India). A decoupling between the PF and economic growth was observed in most countries. The high PF per capita in developed economies was mainly driven by imports from developing countries rather than domestic P applications. Our results also highlighted that international trade had two impacts on global P management. Firstly, it reduced the total global P demand from agricultural production by 16%; secondly, it intensified the imbalance of local P consumption. Therefore, the future sustainable management of P requires consideration of the original suppliers and final consumers along the global supply chains and the associated consequences on P management from both local and global perspectives.

One-pot fabrication of Mo1-xWxS2 alloy nanosheets as SERS substrates with highly Raman enhancement effect and long-term stability.

A new Mo1-xWxS2 two-dimensional nanosheets were prepared by the one-pot method. After certain Mo atoms in MoS2 were replaced by W ones in a hydrothermal reduction procedure, Mo1-xWxS2 was formed on the Mo foil. Well enhanced Mo1-xWxS2 nanosheets were prepared when the sodium tungstate concentration got under control. Various characterizations were carried out, which indicate that Mo1-xWxS2 nanosheets with good crystallinity. Compared with MoS2, the Raman intensity of Rhodamine 6G (10-6 M) was amplified by 1.7 times with Mo1-xWxS2 nanosheets as the substrate. The characteristic Raman peaks could still be clearly distinguished until the concentration of Rhodamine 6G (R6G), Methylene blue (MB) and Crystal violet (CV) down to 10-8, 10-8 and 10-7 M, respectively. With abundant edge active sites that facilitate charge transfer, Mo1-xWxS2 nanosheets could better enhance SERS signals of target detection molecules and get a good linear relationship exists within the concentration and Raman peak strength. In addition, R6G SERS detection also shows excellent reproducibility and long-term stability of this TMDs SERS substrate.

Synergies in sustainable phosphorus use and greenhouse gas emissions mitigation in China: Perspectives from the entire supply chain from fertilizer production to agricultural use.

Synergies to achieve high phosphorus (P) use efficiency (PUE) and mitigate greenhouse gas (GHG) emissions are critical for developing strategies aimed toward agricultural green development. However, the potential effects of such synergies in the entire P supply chain through optimizing P management in crop production are poorly understood. In this study, a partial life cycle of a GHG emissions model was developed to quantify the P-related GHG emissions in the entire P supply chain in China. Our results showed that 16.3 kg CO2-equivalent (CO2-eq) was produced from the entire P supply chain per unit of P used for grain agriculture (maize, rice, and wheat). P-related GHG emissions in China increased more than five-fold from 1980 (7.2 Tg CO2-eq) to 2018 (44.9 Tg CO2-eq). GHG emissions were found to be strongly associated with the intensity of grain production in China, and they varied considerably across production regions owing to the differences in the P fertilizer production efficiency. Mineral P fertilizer use in crop production was the primary source of P-related GHG emissions. The results suggest that sustainable P management by matching mineral P fertilizer rates and fertilizer types with crop needs can mitigate GHG emissions by 10.8-27.7 Tg (24.0-65.1%). Moreover, this can improve PUE and reduce mineral P input by 0.7-1.4 Tg (24.0-46.0%). These findings highlight that potential synergies between high PUE and low P-related GHG emissions can be achieved via sustainable P management, thereby enhancing green agricultural development in China and other regions worldwide.

Integrating life cycle assessment and a farmer survey of management practices to study environmental impacts of peach production in Beijing, China.

While intensive peach production has expanded rapidly in recent years, few studies have explored the environmental impacts associated with specific regional systems or the optimal management strategies to minimize associated environmental risks. Here, data from a survey of 290 native farmers were used to conduct a life cycle assessment to quantify the acidification potential (AP), global warming potential (GWP), eutrophication potential (EP), and reactive nitrogen (Nr) losses in peach production in Pinggu District, Beijing. Total annual Nr losses, and GWP, AP, and EP values for peach production in Pinggu District were respectively 10.7 kg N t-1, 857 kg CO2-eq t-1, 12.9 kg SO2-eq t-1, and 4.1 kg PO4-eq t-1. The principal driving factors were fertilizer production, transportation, and application, which together accounted for 94%, 67%, 75%, and 94% of Nr losses, GWP, AP, and EP, respectively. In the high yield, high nitrogen-use efficiency (HH) group, relative values of Nr losses, GWP, AP, and EP were respectively 33%, 25%, 39%, and 32% lower than the overall averages for 290 orchards. Further analyses indicate that improved farming practices such as decreasing application rates of fertilizers, increasing proportion of base fertilization rate, and proper fertilization frequency in the HH group were the main reasons for these orchards' better performance in peach yields and partial factor productivity of nitrogen fertilizer, and their reduced environmental impacts. These results highlight the need to optimize nutrient management in peach production in order simultaneously to realize both environmental sustainability and high productivity in the peach production system.

Toward the sustainable use of mineral phosphorus fertilizers for crop production in China: From primary resource demand to final agricultural use.

Sustainable phosphorus (P) management is crucial to both food security and environmental conservation. The optimization of P input from mineral fertilizers has been advocated as an effective approach to improve P use efficiency. However, strategies for maximizing P use efficiency by linking soil-crop systems and fertilizer types with the P flow, from a whole P supply chain perspective, are lacking. In this study, a meta-analysis and substance flow analysis (SFA) were employed to evaluate the effects of different mineral P fertilizer types on crop yield and P flow from rock phosphate (RP) exploitation to P use in China. Compared to single superphosphate (SSP), triple superphosphate (TSP), and calcium magnesium phosphate (CMP), a significantly higher yield was obtained when diammonium phosphate (DAP) and monoammonium phosphate (MAP) were used 2005 onwards. However, P loss, from RP extraction to application, was 24% higher for DAP and MAP than for SSP, TSP, and CMP. DAP and MAP use led to a 6% larger P footprint than SSP, TSP, and CMP use. The P use efficiency could be improved by 22%, 36%, and 40% in wheat, maize, and rice production, respectively, by integrating the soil-crop system with mineral P fertilizer types, while P loss and P footprint could be reduced by 13% and 17%, respectively. These results indicate that P use efficiency can be significantly improved by integrating mineral P fertilizer types with soil-crop systems, providing an effective approach for RP exploitation to improve P use efficiency and alleviate the overexploitation of RP.

Integrated wheat-maize straw and tillage management strategies influence economic profit and carbon footprint in the Guanzhong Plain of China.

Appropriate straw and tillage management strategies increase grain yields, and promote atmospheric carbon dioxide (CO2) mitigation through soil organic carbon (SOC) sequestration. However, little is known about economic parameters and carbon footprint (CF, defined as total greenhouse gases emission from the whole life cycle perspective) of intensive wheat (Triticum aestivum L.)-maize (Zea mays L.) double cropping production under different integrated strategies of straw-return and tillage. To quantify the differences of straw-return and tillage integrated strategies in economic parameters and carbon sustainability, a field experiment was established in 2008 in which six integrated strategies were evaluated: straw return of both maize and wheat (MR-WR), MR-WR with subsoiling to ~40 cm depth after maize harvest (MS-WR), single straw return of wheat (MN-WR), single straw return of maize (MR-WN), MR-WN with subsoiling to ~40 cm depth after maize harvest (MS-WN) and no straw return (MN-WN). Results showed that the MS-WR had the greatest grain yields of both wheat and maize, gross revenue and economic profit with increases of 45.5%, 35.6%, 26.5%, and 79.7% relative to the MN-WN, respectively. Compared with the initial SOC level, the SOC stock increased by 22.9% under MS-WR, following by MR-WR (16.0%), MS-WN (11.6%), MR-WN (8.0%), MN-WR (5.1%), and MN-WN (-3.8%). The MS-WR reduced the net CF and net CF per economic profit by 35.4% and 64.1% relative to the MN-WN although it elevated the CF by 25.3%. Therefore, adopting the integrated strategies of both maize and wheat straw return with subsoiling to ~40 cm depth after maize harvest represented an economically and C-friendly optimal field management practice for intensive wheat-maize double cropping production in the Guanzhong Plain or other regions with similar environmental conditions in the world.

Anthropogenic phosphorus flows under different scenarios for the city of Stockholm, Sweden.

Today, concerns prevail about the unsustainable use of phosphorus and worldwide eutrophication, thus requiring efficient management of phosphorus flows. With increasing population and associated urban growth, urban management of phosphorus flows in the perspectives of recycling, eutrophication and total budget becomes increasingly important. This study mapped phosphorus flows for a reference year (2013) and a future year (2030) using different scenarios for the city of Stockholm, Sweden. The results indicated that the Swedish goal of recycling phosphorus from wastewater would cover the majority of the total phosphorus budget for Stockholm. However, in 2013, only 10% of phosphorus was recycled for agricultural use, around half of which was from sewage sludge and the other half from food waste. Almost 50% of total phosphorus was sent to landfill/mining waste capping with sewage sludge, for economic reasons and lack of market. Among the scenarios of upstream and downstream urban management options studied in combination with population growth, recovery of phosphorus from sewage sludge had the greatest potential to increase the fraction recycled to agriculture. However, only upstream measures, e.g. changed diet, were able to reduce the total phosphorus budget. Urban management of phosphorus flows based on the different perspectives of recycling, eutrophication or total budget was shown to potentially result in different preferred management actions and both upstream and downstream measures need to be considered. Moreover, management needs to pay attention to small but environmentally sensitive flows, particularly when setting city goals on phosphorus recycling by percentage in a large budget.

Nutrient loadings from urban catchments under climate change scenarios: case studies in Stockholm, Sweden.

Anthropogenic nutrient emissions and associated eutrophication of urban lakes are a global problem. Future changes in temperature and precipitation may influence nutrient loadings in lake catchments. A coupling method, where the Generalized Watershed Loading Functions method was tested in combination with source quantification in a Substance Flow Analysis structure, was suggested to investigate diffuse nutrient sources and pathways and climate change effects on the loadings to streamflow in urban catchments. This method may, with an acceptable level of uncertainty, be applied to urban catchments for first-hand estimations of nutrient loadings in the projected future and to highlight the need for further study and monitoring. Five lake catchments in Stockholm, Sweden (Råcksta Träsk, Judarn, Trekanten, Långsjön and Laduviken) were employed as case studies and potential climate change effects were explored by comparing loading scenarios in two periods (2000-2009 and 2021-2030). For the selected cases, the dominant diffuse sources of nutrients to urban streamflow were found to be background atmospheric concentration and vehicular traffic. The major pathways of the nitrogen loading were suggested to be from both developed areas and natural areas in the control period, while phosphorus was indicated to be largely transported through surface runoff from natural areas. Furthermore, for nitrogen, a modest redistribution of loadings from surface runoff and stormwater between seasons and an increase in the annual loading were suggested for the projected future climate scenarios as compared to the control period. The model was, due to poor monitoring data availability, only able to set an upper limit to nutrient transport by groundwater both in the control period and the future scenarios. However, for nitrogen, groundwater appeared to be the pathway most sensitive to climate change, with a considerable increase and seasonal redistribution of loadings. For phosphorus, loadings by different pathways were apparently less sensitive to climate change.