Agriculture faces great challenges to ensure global food security by increasing yields while reducing environmental costs. Here we address this challenge by conducting a total of 153 site-year field experiments covering the main agro-ecological areas for rice, wheat and maize production in China. A set of integrated soil-crop system management practices based on a modern understanding of crop ecophysiology and soil biogeochemistry increases average yields for rice, wheat and maize from 7.2 million grams per hectare (Mg ha(-1)), 7.2 Mg ha(-1) and 10.5 Mg ha(-1) to 8.5 Mg ha(-1), 8.9 Mg ha(-1) and 14.2 Mg ha(-1), respectively, without any increase in nitrogen fertilizer. Model simulation and life-cycle assessment show that reactive nitrogen losses and greenhouse gas emissions are reduced substantially by integrated soil-crop system management. If farmers in China could achieve average grain yields equivalent to 80% of this treatment by 2030, over the same planting area as in 2012, total production of rice, wheat and maize in China would be more than enough to meet the demand for direct human consumption and a substantially increased demand for animal feed, while decreasing the environmental costs of intensive agriculture.

Increasing nitrogen (N) and phosphorus (P) inputs have greatly contributed to the increasing food production in China during the last decades, but have also increased N and P losses to the environment. The pathways and magnitude of these losses are not well quantified. Here, we report on N and P use efficiencies and losses at a national scale in 2005, using the model NUFER (NUtrient flows in Food chains, Environment and Resources use). Total amount of "new" N imported to the food chain was 48.8 Tg in 2005. Only 4.4.Tg reached households as food. Average N use efficiencies in crop production, animal production, and the whole food chain were 26, 11, and 9%, respectively. Most of the imported N was lost to the environment, that is, 23 Tg N to atmosphere, as ammonia (57%), nitrous oxide (2%), dinitrogen (33%), and nitrogen oxides (8%), and 20 Tg to waters. The total P input into the food chain was 7.8 Tg. The average P use efficiencies in crop production, animal production, and the whole food chain were 36, 5, and 7%, respectively. This is the first comprehensive overview of N and P balances, losses, and use efficiencies of the food chain in China. It shows that the N and P costs of food are high (for N 11 kg kg(-1), for P 13 kg kg(-1)). Key measures for lowering the N and P costs of food production are (i) increasing crop and animal production, (ii) balanced fertilization, and (iii) improved manure management.

Chinese agriculture has been developing fast towards industrial food production systems that discharge nutrient-rich wastewater into rivers. As a result, nutrient export by rivers has been increasing, resulting in coastal water pollution. We developed a Model to Assess River Inputs of Nutrients to seAs (MARINA) for China. The MARINA Nutrient Model quantifies river export of nutrients by source at the sub-basin scale as a function of human activities on land. MARINA is a downscaled version for China of the Global NEWS-2 (Nutrient Export from WaterSheds) model with an improved approach for nutrient losses from animal production and population. We use the model to quantify dissolved inorganic and organic nitrogen (N) and phosphorus (P) export by six large rivers draining into the Bohai Gulf (Yellow, Hai, Liao), Yellow Sea (Yangtze, Huai) and South China Sea (Pearl) in 1970, 2000 and 2050. We addressed uncertainties in the MARINA Nutrient model. Between 1970 and 2000 river export of dissolved N and P increased by a factor of 2-8 depending on sea and nutrient form. Thus, the risk for coastal eutrophication increased. Direct losses of manure to rivers contribute to 60-78% of nutrient inputs to the Bohai Gulf and 20-74% of nutrient inputs to the other seas in 2000. Sewage is an important source of dissolved inorganic P, and synthetic fertilizers of dissolved inorganic N. Over half of the nutrients exported by the Yangtze and Pearl rivers originated from human activities in downstream and middlestream sub-basins. The Yellow River exported up to 70% of dissolved inorganic N and P from downstream sub-basins and of dissolved organic N and P from middlestream sub-basins. Rivers draining into the Bohai Gulf are drier, and thus transport fewer nutrients. For the future we calculate further increases in river export of nutrients. The MARINA Nutrient model quantifies the main sources of coastal water pollution for sub-basins. This information can contribute to formulation of effective management options to reduce nutrient pollution of Chinese seas in the future.

No abstract

After significant increases in livestock productivity, China now needs to improve efficiency and environmental performance.

Background Crop production in China has been greatly improved by increasing phosphorus (P) fertilizer input, but overuse of P by farmers has caused low use efficiency, increasing environmental risk and accumulation of P in soil. From 1980 to 2007, average 242 kg P ha−1 accumulated in soil, resulting in average soil Olsen P increasing from 7.4 to 24.7 mg kg−1. China is facing huge challenges to improve P use efficiency through optimizing corresponding technology and policies. The problem is exacerbated because people have been shifting their diet from plant-based to animalenriched foods. This results in higher P load in the food chain and lower P use efficiency. Scope A multidisciplinary approach has been used to improve P management at the field and national level in China. Management strategies based on the soil and on the plant rhizosphere have been developed to increase efficient use of P. A national soil testing and fertilizer recommendation program has been used since 2005 to control build-up and maintenance of P levels. Interactions between root growth and the rhizosphere have been manipulated in intercropping systems and plant genetic traits have been exploited. Phosphorus surplus is highly associated with animal concentrated feed. Conclusions The P-saving potential by the integrated P management strategies of P flow reaches 1.46 Mt P in 2050 compared to 2005.

China's pig production has increased manifold in the past 50 years, and this has greatly affected the nitrogen and phosphorus use and losses in the pig production sector. However, the magnitude of these changes are not well-known. Here, we provide an in-depth account of the changes in pig production--N and P use and total N and P losses in the whole pig production chain during the period 1960-2010--through simulation modeling and using data from national statistics and farm surveys. For the period of 2010-2030, we explored possible effects of technological and managerial measures aimed at improving the performances of pig production via scenario analysis. We used and further developed the NUtrient flows in Food chains, Environment and Resources use (NUFER) model to calculate the feed requirement and consumption, and N and P losses in different pig production systems for all the years. Between 1960 and 2010, pig production has largely shifted from the so-called backyard system to landless systems. The N use efficiencies at fattener level increased from 18 to 28%, due to the increased animal productivity. However, the N use efficiencies at the whole-system level decreased from 46 to 11% during this period, mainly due to the increase of landless pig farms, which rely on imported feed and have no land-base for manure disposal. The total N and P losses were 5289 and 829 Gg in 2010, which is 30 and 95 times higher than in 1960. In the business as usual scenario, the total N and P losses were projected to increase by 25 and 55% between 2010 and 2030, respectively. Analyses of other scenarios indicate that packages of technological and managerial measures can decrease total N and P losses by 64 and 95%, respectively. Such improvements require major transition in the pig production sector, notably, in manure management, herd management, and feeding practices.

The largest livestock production and greatest fertilizer use in the world occurs in China. However, quantification of the nutrient flows through the manure management chain and their interactions with management-related measures is lacking. Herein, we present a detailed analysis of the nutrient flows and losses in the "feed intake-excretion-housing-storage-treatment-application" manure chain, while considering differences among livestock production systems. We estimated the environmental loss from the manure chain in 2010 to be up to 78% of the excreted nitrogen and over 50% of the excreted phosphorus and potassium. The greatest losses occurred from housing and storage stages through NH emissions (39% of total nitrogen losses) and direct discharge of manure into water bodies or landfill (30-73% of total nutrient losses). There are large differences among animal production systems, where the landless system has the lowest manure recycling. Scenario analyses for the year 2020 suggest that significant reductions of fertilizer use (27-100%) and nutrient losses (27-56%) can be achieved through a combination of prohibiting manure discharge, improving manure collection and storages infrastructures, and improving manure application to cropland. We recommend that current policies and subsidies targeted at the fertilizer industry should shift to reduce the costs of manure storage, transport, and application.