O. Oenema’s research while affiliated with Wageningen University & Research and other places

Our food system drives global environmental change, and differences in environmental concerns of consumers may cause negative environmental 'spillover effects' in less concerned countries. While food system transformation is increasingly recognised as crucial for mitigating such negative environmental spillovers, possible unintended negative environmental consequences in other regions and/or economic sectors have received less attention. Using an integrated environmental-economic modelling framework and scenario analyses, we explored options for more sustainable food systems and to mitigate the negative environmental spillovers from trading partners to China. We found that doubling novel soy-based food (soy-based meat) consumption while reducing pork consumption in China decreased Chinese economy-wide emissions of greenhouse gases (GHGs) by 1 % and acidification pollutants by 3 %. However, it increased Chinese economy-wide emissions of eutrophication pollutants by 2 %, driven by the increased production of soy-based food and other food with relatively high emission intensities of eutrophication pollutants. Combining a dietary shift with the adoption of cleaner cereals production technology for half of the current resources used for cereals production decreased Chinese economy-wide emissions of GHGs by 1 %, acidification pollutants by 7 %, and eutrophication pollutants by 3 %, but required capital reallocation from other sectors. Implementing a unilateral environmental policy in China (i. e., implementing incentive-based emission permits to reduce emissions of all pollutants by 3 % annually) increased economy-wide emissions of GHGs in trading partners by 2 %. This 'carbon leakage' emerges due to the shift of production of products with relatively high emission intensities (i.e., nitrogen fertiliser and livestock) from China to its trading partners through international trade. We demonstrate that indirect environmental impacts are crucial to consider when analysing the economy-wide consequences of food system transformations, as these indirect impacts may inadvertently affect other regions and/or economic sectors that were not initially targeted. Our study offers policymakers insights into designing effective policies for more sustainable food systems and sheds light on trade-offs among competing environmental and economic goals.

Nitrous oxide (N 2 O) is a potent greenhouse gas and causes stratospheric ozone depletion. While the emissions of N 2 O from soil are widely recognized, recent research has shown that terrestrial plants may also emit N 2 O from their leaves under controlled laboratory conditions. However, it is unclear whether foliar N 2 O emissions are universal across varying plant taxa, what the global significance of foliar N 2 O emissions is, and how the foliage produces N 2 O in situ. Here we investigated the abilities of 25 common plant taxa, including trees, shrubs and herbs, to emit N 2 O under in situ conditions. Using ¹⁵ N isotopic labeling, we demonstrated that the foliage‐emitted N 2 O was predominantly derived from nitrate. Moreover, by selectively injecting biocide in conjunction with the isolating and back‐inoculating of endophytes, we demonstrated that the foliar N 2 O emissions were driven by endophytic bacteria. The seasonal N 2 O emission rates ranged from 3.2 to 9.2 ng N 2 O–N g ⁻¹ dried foliage h ⁻¹ . Extrapolating these emission rates to global foliar biomass and plant N uptake, we estimated global foliar N 2 O emission to be 1.21 and 1.01 Tg N 2 O–N year ⁻¹ , respectively. These estimates account for 6%–7% of the current global annual N 2 O emission of 17 Tg N 2 O–N year ⁻¹ , indicating that in situ foliar N 2 O emission is a universal process for terrestrial plants and contributes significantly to the global N 2 O inventory. This finding highlights the importance of measuring foliar N 2 O emissions in future studies to enable the accurate assigning of mechanisms and the development of effective mitigation.

Nitrogen (N) budgets at farm level are influenced by N fertilisation recommendations. In this study, we reviewed and analysed the underlying principles and methods of N fertilisation recommendations in ten West European countries, to identify similarities and differences, and develop suggestions for reconsideration and improvement. An analysis of national official documents on N fertilisation recommendations revealed that there were three main categories of calculation methods: (i) ‘N mass balances’ (France, Italy, Spain), (ii) ‘Corrected standards’ (Germany, Netherlands, Switzerland, Luxembourg), and (iii) ‘Pre‐parameterised calculations’, which rely on a soil N supply typology (United Kingdom, Ireland, Belgium). In total 16 variables were identified in the calculation methods. The more complex methods use 10 (Italy, France), while the simplest only rely on 3 (Luxembourg). The most common variables include the availability of N in manure, the N uptake by a crop, and the N released by crop residues. Few countries explicitly consider N losses to ground and surface waters or to the atmosphere in the calculation methods. In some countries, the N fertilisation recommendation has a voluntary status, in other countries a legal one (caps on maximum allowable N rates). We compared the N fertiliser recommendations for a wheat crop grown on a farm with livestock, and for a farm with a diverse arable crop rotation without livestock. Across the 10 countries, large differences in the N fertilisation calculation methods and resulting N recommendations existed for the two management scenarios, ranging from almost no fertilisation to 135 kg N ha ‐1 , and from 111 to 210 kg N ha ‐1 , respectively. The differences were not accounted for by the complexity of the equations used, but rather resulted from contrasting reference values for N availability in manure, N uptake by crop and N leaching. However, the study concluded that standardisation of the method to calculate N fertilisation recommendations is likely to be counterproductive as there are no objective reasons to favour one method more than the others. Nonetheless, improvements in N use efficiency are necessary. Farm scale mass balance, combined with parameters such as minimum residual soil mineral N test at harvest was suggested as being an important consideration. This article is protected by copyright. All rights reserved.

In 2015, 17 Sustainable Development Goals (SDGs) were approved, including SDG13, which addresses actions to increase carbon capture (CO2-C storage) for climate change mitigation. However, no analytical procedures have been defined for quantifying soil organic carbon (SOC) sequestration. This paper presents a rapid tool for guiding farmers and for monitoring SOC sequestration in farmer fields. The tool consists of multiconstituent soil analyses through near-infrared spectroscopy (NIRS) and an SOC mineralization model. The tool provides forecasts of SOC sequestration over time. Soil analyses by NIRS have been calibrated and validated for farmer fields in European countries, China, New Zealand, and Vietnam. Results indicate a high accuracy of determination for SOC (R 2 ≥ 0.93), and for inorganic C, soil texture, and soil bulk density. Permanganate oxidizable soil C is used as proxy for active SOC, to detect early management-induced changes in SOC contents, and is also quantified by NIRS (R2 = 0.92). A pedotransfer function is used to convert the results of the soil analyses to SOC sequestration in kg·ha−1 C as well as CO2. In conclusion, the tool allows fast, quantitative, and action-driven monitoring of SOC sequestration in farmer fields, and thereby is an essential tool for monitoring progress of SDG13.

Nutrient management is arguably a key factor for achieving several of the UN Sustainability Development Goals. It plays a key role in the production of sufficient amounts of nutritious food, while poor nutrient management leads to nutrient losses (notably of nitrogen (N) and phosphorus (P)) and contributes to air and water pollution and biodiversity loss. Nutrient management in China is complicated because of the diversity in farming systems and environments, the countless number of farm households and small farms, and the fragmented agricultural supply and advisory system. Current nutrient management in China’s agriculture has become a global concern because of the implications of the large N and P inputs and losses.In this perspective, we identify and discuss several barriers for implementing environmentally-sound nutrient management, and highlight that farmers currently have limited farm-specific techniques, tools and incentives for precision and environmentally sound nutrient management. Most crop farmers manage primarily by choosing fertilizer bag size and nutrient formulation, while many livestock farmers have a headache of manure management, because of a lack of appropriate manure recycling opportunities. We argue that nutrient management in China is at the crossroads; decisions have to be made about the development and testing of farm-specific techniques and tools to provide farmers a customary dashboard with indicators and a steering wheel for precision and environmentally-sound nutrient management. Likewise, integrated crop-livestock systems and sustainability-driven farm business models have to be developed, within the context of Agriculture Green Development, which aims at greening agriculture and enhancing ecosystem services. There is also a need for in-depth and long-term studies of whole farming systems to better understand the impact of farmers’ decisions on nutrient cycling, use efficiency and losses, to test and improve nutrient management tools, and to explore the effects of policy measures. Such approaches could be applied and tested first in Science and Technology Backyards and then up-scaled to other villages and counties.

Feeding animals more low-opportunity-cost feed products (LCFs), such as food waste and by-products, may decrease food–feed competition for cropland. Using a feed allocation optimization model that considers the availability of feed sources and animal requirements for protein and energy, we explored the perspectives of feeding more LCFs to animals in China. We found that about one-third of the animal feed consisted of human-edible products, while only 23% of the available LCFs were used as feed during 2009–2013. An increased utilization of LCFs (45–90 Mt) could potentially save 25–32% of feed-producing cropland area without impairing livestock productivity. Parallelly, about one-third of feed-related irrigation water, synthetic fertilizer and greenhouse gas emissions would be saved. Re-allocating the saved cropland could sustain the food energy demand of 30–185 million people. Achieving the potentials of increased LCF use requires improved technology and coordination among stakeholders.

Low-protein feeding is a strategy used to decrease nitrogen excretion and ammonia (NH3) emissions from animal manure, while maintaining productivity. The optimal protein content depends on many factors, including the type, age, and production level of the animal, as well as the availability, composition, and digestibility of the feed ingredients. Farmers in many developing countries lack information about the protein content of feed and about low-protein feeding, including those in China. This lack of information hinders the making of accurate NH3 emission inventories and strategies for reducing these emissions. We determined farmers’ knowledge and perceptions of low-protein feeding in 338 livestock farms, and the actual protein content of 591 feed samples collected from China. Farmers knew little about protein and low-protein feeding; they simply followed the instructions from feed-delivering companies or contracting companies. The mean protein content of the dairy cows’ diets (159 ± 20 g/kg DM) was relatively low. Layer hens’ diets had a mean protein content of 184 ± 22 g/kg DM, and 14% of their diets were in excess of requirement. Broiler farms used compound feed, of which 23% were in excess of requirement and 15% were deficient in protein. Overall, the mean protein contents were close to the recommended levels for low-protein animal feeding, according to national guidelines, which are similar to the guidelines of the National Research Council (NRC) of the United States. However, there were large variations between farms, suggesting the scope for improvement on many farms. Our research provides farmers, feed companies, policy makers, and institutions with useful information to improve feed management, and to improve the inventories and assessment of NH3 emissions from animal production.