Improved Manure Management Research Articles

Effect of black soldier fly larvae frass addition on humus content during low temperature co-composting

Initiating aerobic fermentation under low temperature is the main challenge for winter livestock manure composting. This study aims to address this issue by applying black soldier fly larvae (BSFL) frass as a co-composting additive to enhance the low-temperature composting process. Specifically, this work explored the effects of chicken manure and BSFL frass co-composting on the temperature, humus content, and microorganisms with fresh weight ratio of 2:1, 1:1, 1:2 (w/w) at 6 °C. The result showed frass could rapidly rise the temperature to 50 °C and significantly increased the humus content by 15.6 % ∼ 26.3 %. Moreover, microbial analysis revealed that Sphingobacteriaceae accelerated temperature rise via low-temperature reproduction, creating proper temperature for thermophilic bacteria (Truepera and Georgia). Additionally, Cellulomonas and other bacteria promoted organic matter degradation and participated in humus formation. This study presents a novel solution for low-temperature composting, providing practical insights for improving manure management in winter.

Carbon footprints, mitigation effects and economic performance of dairy farm systems in Inner Mongolia

CONTEXTReducing the GHG emissions intensity of milk production has become a key sustainability challenge for the dairy sector. Addressing this challenge requires thorough understanding of the current GHG emission levels of individual farms, the practices influencing GHG emissions, and the economic trade-offs associated with reducing those emissions. OBJECTIVEQuantify the carbon footprint (CF) and economic performance of milk production in Inner Mongolia (the main dairy farming region in China), and understand the main contributing factors to them. The effects of potential mitigation options at dairy farm system level were evaluated. METHODS: Life cycle assessment methodology was used to analyze the CF of 15 dairy farms (with year-round cow housing and crop feeding) selected for different milk production levels, herd structures and diet composition. RESULTS AND CONCLUSIONSThe average CF per kg of fat and protein corrected milk (FPCM; after allocation to milk) was 2.3 kg carbon dioxide equivalents (CO2-eq) (1.5–3.4 kg CO2-eq). Emissions related to feed production, manure management and enteric fermentation were the top three GHG emission sources and contributed an average of 27% (5%–46%), 28% (19%–38%) and 18% (14%–25%), respectively, to total emissions. The average cost of the farm system per ton FPCM was USD 540 per year. Feed costs dominated at 70% of the total costs. The CF of milk was negatively correlated with profit per kg FPCM. Mitigation potential of the CF of dairy production for single mitigation strategies ranged from 2.3% to 20.0% compared with business as usual, and combined mitigation measures could reduce emissions by 48.3%. The most effective mitigation measures should focus on decreasing N-fertilizer use per ha for feed crop production and increasing feed crop yield, adjusting herd structure for milk productivity and using localized feed inputs. All mitigation measures had a positive impact on farm profit, except for the improved manure management (changing the farms using manure composting to a static compost system and changing natural storage to direct land application). Therefore, the combination of crop and dairy production and manure management offer the greatest potential to reduce the GHG emissions from Inner Mongolia dairy farm systems. Economic subsidies and extension of findings to farmers might encourage more rapid adoption of these technologies. SIGNIFICANCEThe insights from our study can provide guidance for defining and prioritizing mitigation strategies for dairy production to reduce GHGs emission in other rapidly developing countries and regions with crop-based housed-cow dairy production.

The ecological potential of manure utilisation in small-scale biogas plants

The main sources of greenhouse gas emissions, accelerating global climate change, are heat and electricity generation. To lower these emissions, an expansion of renewable energy usage is required. Biogas plants, a flexible renewable power source, are one possibility, and are already widely established in the European energy system. This study focuses on the utilisation of raw manure in closed systems to reduce direct CO2eq. emissions. It is the first to compare manure treatment in different types of small-scale biogas applications and under the impact of increasing temperatures resulting from climate change. The environmental impact in terms of four impact categories is evaluated by means of a life cycle assessment. Two cases are investigated: a biogas plant with either subsequent combustion in a combined heat and power plant or the direct usage of biogas as a simplified and less expensive application. The analysis shows that the first case yields –173 kgCO2eq. per m3 of manure, whereas the simplified one causes 20.9 kgCO2eq. per m3 of manure. If the first case is scaled with the currently existing number of small-manure plants in Germany, emissions of 464 mil. t CO2 eq. are mitigated per year. With increasing average annual temperatures, higher manure credits are generated and so the emissions of both plant options are reduced to –264and –69.5 kgCO2 eq. per m3 of manure, respectively, ascribing the direct biogas usage reductions of GHG emissions. Consequently, both systems have the potential for reducing emissions due to improved manure management and can contribute to mitigating climate change.

241 Towards More Sustainable Use of Trace Elements in Pig and Poultry Feeding

Abstract Copper and zinc are essential trace elements, which play an important role in a large number of biological functions, including immunity and protection from oxidative stress. When supplied at pharmacological level, they may improve gut health and animal performance, especially during stressful periods. However, because of their low retention, most of the Cu and Zn ingested is excreted, contributing to harmful environmental impacts, such as accumulation in soils and water ecosystems, and toxicity to soil microorganisms and plants. A high level of Zn in feed may also contribute to the development of antibiotic resistance. Finally, Cu and Zn are limited natural resources that should be preserved and better recycled. To find a compromise between the positive and negative effects of Cu and Zn, we need a holistic approach considering animal performance and health, risk of microbial resistance, and risk for the environment. In that perspective, reducing dietary Cu and Zn supplies whilst maintaining satisfactory animal performance appears the most effective approach. However, to safely reduce Cu and Zn supplies, their requirements should be better evaluated and the dietary factors and mechanisms that significantly affect their bioavailability better understood. Improved manure management is another way to better control the risk of soil contamination, by concentrating these elements in organic fertilizers that might be transferred to regions with soil deficiency. In the recent years, the EU regulation on Cu and Zn content of animal feed and organic fertilizers played a major role in reducing their utilization in pig and poultry. For instance in pigs, compared to before 2003, Zn and Cu excretion was reduced by 65% (from 80 to 30 g/pig) and 80% (from 38 to 8 g/pig), respectively, as well as their concentration in excreta (from 2500 to 1000 mg Zn /kg DM ppm and from 1000 to 250 mg Cu /kg DM).

Phosphorus characteristics of Canada-wide animal manures and implications for sustainable manure management with a cleaner environment

Animal manure can be a serious environmental concern if improperly managed, particularly with regard to phosphorus (P). A good understanding on manure P chemistry is required for improving manure management in an environmentally sustainable manner. In the study, 102 representative manure samples collected from farms of major intensive livestock areas of Canada were sequentially fractionated with H2O, 0.5 M NaHCO3, 0.1 M NaOH, and 1.0 M HCl, respectively, for measuring inorganic (Pi) and organic P (Po). Across the manures, total P (TP) ranged from 3.71 to 17.3 g kg−1, with total Pi and available P (i.e., the sum of H2O-Pi and NaHCO3-Pi) accounting for 67.0–92.4 % and 35.6–67.3 % of TP, respectively. Composting reduced the percentages of available P and Po in TP, and meanwhile increased the percentages of moderately stable HCl-Pi. Compared to other P fractions, manure available P increased more rapidly with increases in TP; once manure TP reached 7.8–9.6 g kg−1, further TP increase enhanced transformation to more recalcitrant P (i.e., NaOH-Pi and HCl-Pi). Under Canadian conditions, manure application to meet the demand of crops for N would lead to P buildup in the soil at rates of 6.1–41.6 kg P ha−1 yr−1, increasing runoff P loss risk. Manure compost and poultry manure tend to cause rapid P buildup in the soil after land application and become a long-term P source for runoff losses. The results help to develop scientifically-sound manure-specific P management technologies which would enable farmers to achieve sustainable crop production with improved environment.

Opportunities to implement manureshed management in the Iowa, North Carolina, and Pennsylvania swine industry.

The U.S. swine industry is diverse, but opportunities exist to strategically improve manure management, especially given much of the industry's vertical integration. We investigate opportunities for improving manureshed management, using swine production examples in Iowa, North Carolina, and Pennsylvania as a lens into historical trends and the current range of management conditions. Manure management reflects regional differences and the specialized nature of hog farms, resulting in a large range of land bases required to assimilate manure generated by these operations. Selected representative farm scenarios were evaluated on an annual basis; farm-level manuresheds were largest for Pennsylvania sow farms and smallest for North Carolina nursery farms. Compared with nitrogen-based manuresheds, phosphorus-based manuresheds were up to 12.5 times larger. Technology advancements are needed to promote export of concentrated nutrients, especially phosphorus, from existing "source" manuresheds to suitable croplands. The industry is dynamic, as revealed by historical analysis of the siting of hog barns in Pennsylvania, which are currently trending toward the north and west where there is greater isolation to prevent the spread of disease and a larger land base to assimilate manure. Industry expansion should focus on locating animals in nutrient "sink" areas.

Groundwater contamination risks with manure-borne microorganisms under different land-application options

There is a huge potential for recycling animal manure in agricultural farms, but fecal microorganisms from land-applied animal manure can join shallow groundwater through leaching especially in alluvial formations. Thus, this study investigated the leaching rate of total viable count (TVC) below a 1.1-m soil depth in a field lysimeter planted with rice–maize–rice rotation, where the rotation received different treatments, i.e., chemical fertilizer, dry manure, fresh manure, alternate wetting and drying (AWD) irrigation, and traditional irrigation. Leachate samples of six major irrigation/rainfall events were collected and analyzed for TVC concentration. In the Aman rice season, manure application had a significantly higher TVC leaching (5.5 × 106 colony forming units (CFU) per milliliter) than the no-manure treatment (8.2 × 104 CFU/mL). In the maize season, manure application increased more than one log-scale of TVC leaching concentration. A higher concentration of TVC leaching (3 × 105 CFU/mL) was observed even after 93 d of fresh manure application. The fresh manure had a higher TVC load, and it possibly helped microorganisms survive longer by providing a more manure-like environment in the soil. In the Boro rice season, manure application increased the TVC leaching up to 3–4 log-scale compared with the control treatment. The AWD irrigation increased TVC leaching compared with the continuous irrigation because the desiccation fractures developed in the AWD irrigation helped TVC bypass the organic-rich topsoil. The Boro rice fields had higher TVC leaching than the maize fields with higher manure doses. The study suggests that there is scope to improve manure management to protect the groundwater quality.

Emissions of carbon dioxide and methane from dairy cattle manure

There is an increasing interest in reducing production and emissions of greenhouse gases to combat global warming. Greenhouse gases can be produced through animal production operations. One of the major sources of greenhouse gases emitted from the animal farming is dairy cattle barns. This study measured the CH4 and CO2 emissions from dairy cattle manure decomposition trapped inside the static chambers through anaerobic digestion process by bacteria and at regular intervals by focusing on animal age and manure storage method. Samples were analyzed using gas chromatography for the estimation of CH4 and CO2 emissions. Four Friesian cows were used representing two stages of cow age (3 and 10 years old) and 1 kg of fresh manure samples were collected (feces and mixture of feces with urine). It was found that CH4 and CO2 emissions produced by cattle at the age of 3 years were higher than age of 10 years. In addition, gases emitted from fresh slurry feces were higher than liquid manure for both ages (3 and 10 years). This is due to the fact that the organic matter degradation in the feces and amount of fresh slurry feces is twice the amount of fresh slurry feces used in the liquid manure, as well as the organic matter in the manure mass for the age of 3 years is higher than for the age of 10 years. The findings from this study can provide information for improving manure management practices in animal farms.

Sustainability aspects of milk production in Sweden

AbstractResource use efficiency and economic initiatives point towards using less human‐edible input in ruminant food production. This could also promote the nutrient‐rich dairy products to consumers in comparison with alternative plant‐based drinks. The global population is growing and food production will need to increase to feed more people in the future. The Swedish government has launched a national food strategy, which aims to move Swedish food production towards self‐sufficiency and sustainability, and greater exports. Simultaneously, strong economic development has stimulated consumers to request more high‐value foods, such as meat and refined dairy products. At the same time, public opinion states that today's food production from ruminants is negative for the environment and contributes to climate change. This review assesses some aspects of dietary ingredient composition and feeding choices that can contribute to making Swedish dairy production more sustainable. Efficient dietary methane mitigating strategies can decrease emissions of greenhouse gases in line with European Union targets and avoid major changes in dietary consumption patterns of meat and milk from ruminants. Although feeding management seems to be the most important approach to decrease nitrogen losses, rational use of fertilizers and improved manure management practices on dairy farms should also be considered to decrease the impact of nitrogen losses to the environment.

NUTRIENT USE EFFICIENCY AND LOSSES OF INDUSTRIAL FARMS AND MIXED SMALLHOLDINGS: LESSONS FROM THE NORTH CHINA PLAIN

<List> <ListItem><ItemContent> • Degree of integration of crop and livestock was insufficient on mixed smallholdings. </ItemContent></ListItem> <ListItem><ItemContent> • Liquid manure discharges on industrial farms hamper the closing of nutrient loops. </ItemContent></ListItem> <ListItem><ItemContent> • Coupling with local crop farms is encouraged to achieve integration of crop-livestock systems. </ItemContent></ListItem></List> <fig><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2095-7505-8-1-58/fase-20371-myf-tu1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2095-7505-8-1-58/FASE-20371-MYF-tu1.tif"/></fig> The proportion of industrial livestock in China has increased over the past 30 years, which increases animal performance but causes the decoupling of crop and livestock production. Here, we aimed to quantify nutrient flows, nutrient use efficiency, and nutrient losses in different livestock systems in the North China Plain based on the NUFER-farm model. Activity data were collected by face-to-face surveys on pig and dairy (41 livestock farms) during 2016–2018. The two systems included industrial farms and mixed smallholdings. In mixed smallholdings, 4.0% and 9.6% of pig and dairy feed dry matter (DM) were derived from household farmland, but 4.8% and 9.3% of manure DM recycled to household farmland. Nutrient use efficiency in industrial farms was higher than in mixed smallholdings at animal level, herd level, and system level. To produce 1 kg N and P in animal products, nutrient losses in industrial pig farms (2.0 kg N and 1.3 kg P) were lower than in mixed pig smallholdings, nutrient losses in industrial dairy farms (2.7 kg N and 2.2 kg P) were slightly higher than in mixed dairy smallholdings. Liquid manure discharge in industrial farms was the main losses pathway in contrast to mixed smallholdings. This study suggests that feed localization can reduce nutrient surpluses at the district level. It is necessary to improve manure management and increase the degree of integrated crop-livestock in smallholdings. In industrial farms, it is desirable to increase the liquid manure recycling ratio through cooperating livestock and crop production at the district level.

Operational costs and neglect of end-users are the main barriers to improving manure treatment in intensive livestock farms

Abstract Improving manure management is essential to actualise a more circular economy in agro-ecosystems. However, the drivers of and barriers to improving manure management and recycling are not well understood. We report farmers’ perceptions of manure management techniques on dairy and poultry farms, with a focus on anaerobic digestion, solid–liquid separation, and composting as common techniques used to facilitate manure management and valorisation. We conducted face-to-face interviews with 338 intensive livestock farmers in China. We hypothesised that farmers’ behaviour is differentially influenced by their perceptions of outcomes, social referents, and controlling factors of the manure management techniques, and by farm and farmers’ characteristics. Results indicated that the actual adoption of manure treatment techniques was limited on the surveyed farms (21% dairy farms, 0%–2% poultry farms; other farms were either not equipped with these techniques or the techniques were not used). Most farms had limited cropland and recycled a small but variable percentage of manure (15%–64% for nitrogen and 25%–95% for phosphorus). Farmers’ perceptions of the environmental benefits of manure treatment and incentives from government agencies were identified as key drivers for the adoption of manure management techniques. High operation cost, low benefit-cost ratios, technical failures, and lack of a functioning manure market were identified as main barriers. Farm scale, farmers’ education and identity also influenced farmers’ intention to use manure treatment techniques. Our results indicate that there is need for capacity building in the whole manure management chain, and for monitoring programmes. We argue that greater attention and governmental support should be allocated to (i) the actual operation of treatment techniques (instead of investment subsidies), and (ii) to the end-users of manure treatment products, who need appropriate application machines.

Horse Manure Management by Commercial and Old-Order Amish Equine Operators: Economic and Conservation Implications

Horse operations may produce high amounts of manure per acre/ha and be less aware of recommended manure management practices than livestock farmers, leading to negative environmental impacts. This study compared the manure management practices of two populations of horse owners in the USA state of Missouri, commercial horse operations and an Old-Order Amish community, using data from a 2019 mail survey with a 50% response rate. In commercial operations, manure was more likely to be piled rather than spread directly on fields, which was the Amish practice. The Amish were more likely to use manure for crop production, to indicate that was why they had not explored markets for manure, and to test soil for nutrients. Regression results for factors affecting previous sales/transfers of manure or compost showed that selling was more likely for commercial operations, female operators, and those who had composted manure. Compared to respondents who agreed that manure management had an impact on water quality, those who did not know or were neutral about that statement were more likely to have sold manure. While both groups can improve manure management and are underserved by traditional agricultural information channels, educational efforts should be tailored to their different circumstances.

Greenhouse gas mitigation and rural electricity generation by a novel two-stroke biogas engine

Small-scale anaerobic digestion of wet organic wastes can make positive contributions to climate mitigation, energy security and nutrient cycling in agri-food systems. However, the environmental sustainability of small-scale anaerobic digestion is undermined where lack of capacity to utilize the biogas fuel results in biomethane venting to the atmosphere, contributing to climate change. Policy support for improved manure management in Bali, Indonesia, has resulted in the installation of small (6 m3) anaerobic digesters across 752 Bali cattle breeding units. These 752 remote rural digesters annually vent approximately 75 482 ± 37 741 m3 of biomethane into the atmosphere as a waste, owing to lack of practical means to convert this potential fuel into useful energy. Meanwhile, most of these cattle farms lack access to electricity. This paper describes the performance of a novel, compact and versatile “BioMiniGen” system that provides convenient electricity generation from small-scale biogas production. This innovative system comprises: (i) a simple biogas desulfurizing system; (ii) a two-stroke, single cylinder (63 cc) air-cooled engine; (iii) an electric generator; (iv) an optional CO2 removal unit. Lifecycle assessment indicated that bioelectricity generated by the BioMiniGen would have a smaller environmental footprint than Indonesian grid electricity across 11 impact categories, including a negative global warming burden owing to avoidance of biogas venting. Trade-offs included a larger abiotic depletion burden associated with manufacture of the generators. Over a five-year lifetime, each unit, costing US$500, could generate up to 5971 kWh of electricity and mitigate up to 65.1 Mg CO2 eq., with a greenhouse gas abatement value up to US$13023. Across Bali, up to 898 ± 449 MWh yr−1 bioelectricity could be generated, and 1.92 ± 0.96 Gg CO2 eq. saved. Further pilot trials are needed to ascertain realistic biogas yields from cleaned digesters managed for bioenergy generation alongside manure management. BioMiniGen technology could make an important contribution to energy security for the 1.4 billion people globally who lack access to electricity.

English

The global quest for a sustainable bio-economy has brought to the fore importance of engaging agricultural systems in the production and in practice change. There have been issues limiting farmers from improving the practice of manure management as smart climate technology. The objective of this paper was to highlight the constraints, type, and valuation of manure types and information sources that smallholder dairy farmers find it useful to change practices regarding manure management. In this present study, 336 smallholder dairy farmers were surveyed on various constraints the farmers faced and, on the type, and value of different manure types and information on manure management received by the farmers. The study used descriptive statistics for the variables and compared them using frequency tables. The key findings from this study would support information to stakeholders in inducing climate-smart manure management practices as a climate adaptation practice. The study highlights the type of information systems that determine areas for further investigation as drivers of practice change for smallholder dairy farmers. The paper focuses on these constraints and synthesizes them into factors that determine practice change on manure management by smallholder dairy farmers in order to improve manure management. Key words: Manure management, agricultural information, smallholder dairy farmers, practice change, information value. &nbsp

Predicting nutrient excretion from dairy cows on smallholder farms in Indonesia using readily available farm data.

ObjectiveThis study was conducted to provide models to accurately predict nitrogen (N) and phosphorus (P) excretion of dairy cows on smallholder farms in Indonesia based on readily available farm data.MethodsThe generic model in this study is based on the principles of the Lucas equation, describing the relation between dry matter intake (DMI) and faecal N excretion to predict the quantity of faecal N (QFN). Excretion of urinary N and faecal P were calculated based on National Research Council recommendations for dairy cows. A farm survey was conducted to collect input parameters for the models. The data set was used to calibrate the model to predict QFN for the specific case. The model was validated by comparing the predicted quantity of faecal N with the actual quantity of faecal N (QFNACT) based on measurements, and the calibrated model was compared to the Lucas equation. The models were used to predict N and P excretion of all 144 dairy cows in the data set.ResultsOur estimate of true N digestibility equalled the standard value of 92% in the original Lucas equation, whereas our estimate of metabolic faecal N was −0.60 g/100 g DMI, with the standard value being −0.61 g/100 g DMI. Results of the model validation showed that the R2 was 0.63, the MAE was 15 g/animal/d (17% from QFNACT), and the RMSE was 20 g/animal/d (22% from QFNACT). We predicted that the total N excretion of dairy cows in Indonesia was on average 197 g/animal/d, whereas P excretion was on average 56 g/animal/d.ConclusionThe proposed models can be used with reasonable accuracy to predict N and P excretion of dairy cattle on smallholder farms in Indonesia, which can contribute to improving manure management and reduce environmental issues related to nutrient losses.

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.

Is biogas an energy or a sustainability product? - Business opportunities in the Finnish biogas branch

The business opportunities in the Finnish biogas branch were studied through policy document analysis, analysis of the financial performance, and interviews of the biogas companies (in industrial and farm-scales). Although our study focuses on the case of Finland, many identified features of biogas production can be recognized at least on a European level. The analysis of national policy documents (related to biogas and renewable energy) revealed that even if biogas production and utilization is encouraged, all objectives and measures are rather cautiously formulated and tend to remain on a general level. In addition, economic arguments in policy documents (cost-effectiveness, commercial and business potential, market principles) are emphasized as common criteria for renewable energy technologies, biogas included. The financial performance was studied during 2011–2017 when biogas production more than doubled in Finland (from 52 000 m3 to 110 000 m3). While biogas production is not, in fact, economically very lucrative (the return on investment (ROI) of the studied companies has decreased from 10% to 5% during 2011–2017), there are other partially nonmarket benefits that support biogas production. The larger scale industrial plants’ performance was more stable, most probably due to the gate fees which they obtained from waste treatment. Based on the interviews, the farm-scale plants gained also nonmarket cobenefits from the biogas plant on the farm, such as improved manure management. In addition, both the industrial and the farm-scale plants saw new business opportunities in the future, such as biogas use as traffic fuel and recycling nutrients. Biogas technology also has potential to mitigate climate change and eutrophication. Future policies should more specifically take these benefits and possibilities into account.

Manure Management Practices and Policies in Sub-Saharan Africa: Implications on Manure Quality as a Fertilizer

Manure has been used as a fertilizer since ancient times and if well-managed it can be an asset, promoting sustainable agriculture, and increasing crop production, particularly for smallholder farmers in sub-Saharan Africa (SSA). However, most farmers in SSA do not apply recommended manure management practices, such as roofing animal housing, having a water-proof floor or covering manure during storage, causing large nutrient losses during manure storage, increasing greenhouse gas emissions, and reducing the quality of the manure as a fertilizer. This paper compares manure management practices in representative SSA countries, and summarizes government policies and socio-cultural practices that influence the adoption of good (recommended) manure management practices. Three steps were applied in this analysis: (i) review of manure management practices from various literature sources, (ii) interviews on manure management practices and policies with key stakeholders from 13 SSA countries, and (iii) surveys of manure management practices on small, medium, and large scale farms in Ethiopia and Malawi. The review confirms the potential of manure to improve crop yields and promote sustainable agriculture in SSA. Unfortunately, most SSA countries (a) do not explicitly mention manure management in their policies (b) have different ministries that share responsibilities on manure management, often leading to incoherent policies and abnegation of these responsibilities (c) take limited action to promote good practices or enforce legislation on manure management. Also, the field survey indicated that farmers lack knowledge on manure management. However, farmers are able to access agricultural extension services from both government and non-government agencies, although these extension services rarely included information on improved manure management practices. Extension services that encourage exchange and interaction between farmers were most successful in increasing adoption of good manure management practices, and are recommended. In addition, efforts to improve manure management in SSA should strengthen the enforcement of existing policies and provide an enabling environment for adoption of good manure management practices.

Nitrogen and carbon footprints of dairy farm systems in China and New Zealand, as influenced by productivity, feed sources and mitigations

Three dairy farm systems in China and in New Zealand (NZ) varying in intensity based on level of use of brought-in crop feeds were selected from surveyed data. Nitrogen (N) emissions were estimated using country-specific N and life cycle assessment models. Milk production per cow increased with increased use of grain-based feeds but there was no whole-system difference in energy and land use resource efficiency. The N footprint (∑reactive-N emissions kg-1 milk for cradle-to-farm-gate) was 1.3–2.3 times higher for the housed-cow Chinese farm systems than the year-round pasture-grazing NZ farm systems, associated with greater emissions of all forms of reactive-N. The N footprint decreased with increased feed use and milk production in both countries, mainly due to decreased ammonia emissions. There were similar trends in carbon (C) footprint (total greenhouse gas emissions) of milk, except within NZ where there was no change with feeding level. In NZ, the N loss to water kg-1 milk increased due to the contribution from feed crops. The source of feed was an important determinant of environmental impacts, and changing to low N-footprint feeds decreased the N footprint of milk by up to 10% in both countries. However, manure management was the dominant contributor to the N footprint for all farms, and particularly in China. Mitigation analysis of Chinese farm systems showed the potential to decrease the N footprint of milk by over 30% with improved manure management practices, particularly from utilizing manure that is currently discharged. The largest mitigation potential (up to -25%) in NZ was from ceasing N fertilizer use on pasture and relying on clover N2 fixation. Scenario analysis for late-autumn/winter housing of cows in NZ decreased N loss to water but greatly increased ammonia emissions, resulting in an increase in N and C footprints of up to 21%. Thus, Chinese dairy farms can improve environmental efficiency through sourcing low-impact feeds, improved manure management and integrating manure recycling with feed crops. In contrast, NZ farms can improve environmental efficiency through efficient use of grazed legume-based pastures rather than using crop-feeds or cow housing systems.

Effects of high-sugar grasses and improved manure management on the environmental footprint of milk production at the farm level

Pasture-based milk is increasingly preferred by consumers owing to its perceived socio-economic, animal welfare and environmental benefits. However, nitrogen excretion from pasture-based dairy farming is also a large source of nitrogen leaching and emission of the potent greenhouse gas nitrous oxide. Ryegrass bred to express elevated concentrations of water-soluble carbohydrates (‘high-sugar’ grass; HSG) has been shown to decrease dietary nitrogen excretion in urine of cattle, and may increase milk yields per cow, but it is unclear how this translates to environmental footprints at the farm- and product-levels. This study evaluates, for the first time, the environmental footprint of HSG dairy systems with life cycle analysis, measured as land occupation in addition to global warming, eutrophication, acidification and resource depletion potentials (energy-based and economic allocation methods). Data from meta-analysis and simulation were combined to model a pasture-based dairy farm under a conventional perennial ryegrass-based scenario (Sc-CTR) and an HSG-based scenario (Sc-HSG). In addition, grass type interactions with six manure management permutations were considered, leading to 12 scenarios in total. It was found that eutrophication and acidification potentials per unit of energy-corrected milk could be reduced by 4–6% and 7–11% respectively when switching from Sc-CTR to Sc-HSG, and that these reductions could reach 22% and 40% respectively with more efficient manure management. It is concluded that a simple change in choice of grazing sward may deliver substantial environmental gains, especially when combined with improved farm technology. However, the high costs for improving manure management could drive expansion of HSG pastures as a more attractive short-term measure for farmers, while regulation and access to capital could drive investment in improved manure storage infrastructure and spreading equipment.