Strategies to reduce nutrient pollution from manure management in China

As the demand for livestock products continues to increase in China,so too does the challenge of managing increasing quantities of manure.Urgent action is needed to control point source(housing,storage and processing)and diffuse(field application)pollution and improve the utilization of manure nutrients and organic matter.Here,we review strategies to improve management at each stage of the manure management chain and at different scales.Many strategies require infrastructure investment,e.g.,for containment of all manure fractions.Engineering solutions are needed to develop advanced composting systems with lower environmental footprints and design more efficient nutrient stripping technologies.At the field-scale,there is an urgent need to develop a manure nutrient recommendation system that accounts for the range of manure types,cropping systems,soils and climates throughout China.At the regional scale,coordinated planning is necessary to promote recoupling of livestock and cropping systems,and reduce nutrient accumulation in regions with little available landbank,while minimizing the risk of pollution swapping from one region to another.A range of stakeholders are needed to support the step change and innovation required to improve manure management,reduce reliance on inorganic fertilizers,and generate new business opportunities.

AGRONOMIC AND ENVIRONMENTAL BENEFITS OF REINTRODUCING HERB-AND LEGUME-RICH MULTISPECIES LEYS INTO ARABLE ROTATIONS:A REVIEW

Agricultural intensification and the subsequent decline of mixed farming systems has led to an increase in continuous cropping with only a few fallow or break years,undermining global soil health.Arable-ley rotations incorporating temporary pastures(leys) lasting 1–4 years may alleviate soil degradation by building soil fertility and improving soil structure.However,the majority of previous research on arable-ley rotations has utilized either grass or grassclover leys within ungrazed systems.Multispecies leys,containing a mix of grasses,legumes,and herbs,are rapidly gaining popularity due to their promotion in agri-environment schemes and potential to deliver greater ecosystem services than conventional grass or grass-clover leys.Livestock grazing in arable-ley rotations may increase the economic resilience of these systems,despite limited research of the effects of multispecies leys on ruminant health and greenhouse gas emissions.This review aims to evaluate previous research on multispecies leys,highlighting areas for future research and the potential benefits and disbenefits on soil quality and livestock productivity.The botanical composition of multispecies leys is crucial,as legumes,deep rooted perennial plants(e.g.,Onobrychis viciifolia and Cichorium intybus) and herbs(e.g.,Plantago lanceolata) can increase soil carbon,improve soil structure,reduce nitrogen fertilizer requirements,and promote the recovery of soil fauna(e.g.,earthworms) in degraded arable soils while delivering additional environmental benefits(e.g.,biological nitrification inhibition and enteric methane reduction).Multispecies leys have the potential to deliver biologically driven regenerative agriculture,but more long-term research is needed to underpin evidence-based policy and farmer guidance.

REINTEGRATION OF CROP-LIVESTOCK SYSTEMS IN EUROPE:AN OVERVIEW

Ongoing specialization of crop and livestock systems provides socioeconomic benefits to the farmer but has led to greater externalization of environmental costs when compared to mixed farming systems.Better integration of crop and livestock systems offers great potential to rebalance the economic and environmental trade-offs in both systems.The aims of this study were to analyze changes in farm structure and review and evaluate the potential for reintegrating specialized intensive crop and livestock systems,with specific emphasis on identifying the co-benefits and barriers to reintegration.Historically,animals were essential to recycle nutrients in the farming system but this became less important with the availability of synthetic fertilisers.Although mixed farm systems can be economically attractive,benefits of scale combined with socio-economic factors have resulted in on-farm and regional specialization with negative environmental impacts.Reintegration is therefore needed to reduce nutrient surpluses at farm,regional and national levels,and to improve soil quality in intensive cropping systems.Reintegration offers practical and cost-effective options to widen crop rotations and promotes the use of organic inputs and associated benefits,reducing dependency on synthetic fertilisers,biocides and manure processing costs.Circular agriculture goes beyond manure management and requires adaptation of both food production and consumption patterns,matching local capacity to produce with food demand.Consequently,feed transport,greenhouse gas emissions,nutrient surpluses and nutrient losses to the environment can be reduced.It is concluded that reintegration of specialized farms within a region can provide benefits to farmers but may also lead to further intensification of land use.New approaches within a food system context offer alternatives for reintegration,but require strong policy incentives which show clear,tangible and lasting benefits for farmers,the environment and the wider community.

GREENHOUSE GAS AND AMMONIA EMISSION MITIGATION PRIORITIES FOR UK POLICY TARGETS

Agriculture is essential for providing food and maintaining food security while concurrently delivering multiple other ecosystem services. However,agricultural systems are generally a net source of greenhouse gases and ammonia. They, therefore, need to substantively contribute to climate change mitigation and net zero ambitions. It is widely acknowledged that there is a need to further reduce and mitigate emissions across sectors, including agriculture to address the climate emergency and emissions gap. This discussion paper outlines a collation of opinions from a range of experts within agricultural research and advisory roles following a greenhouse gas and ammonia emission mitigation workshop held in the UK in March 2022. The meeting identified the top mitigation priorities within the UK's agricultural sector to achieve reductions in greenhouse gases and ammonia that are compatible with policy targets. In addition, experts provided an overview of what they believe are the key knowledge gaps, future opportunities and cobenefits to mitigation practices as well as indicating the potential barriers to uptake for mitigation scenarios discussed.

Biochar application to temperate grasslands:challenges and opportunities for delivering multiple ecosystem services

Grasslands(natural,semi-natural and improved)occupy approximately one-third of the terrestrial biosphere and are key for global ecosystem service provision,storing up to 30%of soil organic carbon(SOC).To date,most research on soil carbon(C)sequestration has focused on croplands where the levels of native soil organic matter(SOM)are typically low and significant potential exists to replenish SOM stocks.However,with the renewed push to achieve“net zero”C emissions by 2050,grasslands may offer an additional C store,utilising tools such as biochar.Here,we critically evaluate the potential for biochar as a technology for increasing grassland C stocks,identifying a number of practical,economic,social and legislative challenges that need to be addressed before the widescale adoption of biochar may be achieved.We critically assess the current knowledge within the field of grassland biochar research in the context of ecosystem service provision and provide opinions on the applicability of biochar as an amendment to different types of grassland(improved,semi-improved and unimproved)and the potential effect on ecosystem provision using a range of application techniques in the topsoil and subsoil.We concluded that the key question remains,is it possible for managed grasslands to store more C,without causing a loss in additional ecosystem services?To address this question future research must take a more multidisciplinary and holistic approach when evaluating the potential role of biochar at sequestering C in grasslands to mitigate climate change.