Benefits and trade-offs of replacing synthetic fertilizers by animal manures in crop production in China: A meta-analysis
Zhang, Xiaoying ; Fang, Qunchao ; Zhang, Tao ; Ma, Wenqi ; Velthof, Gerard L. ; Hou, Yong ; Oenema, Oene ; Zhang, Fusuo - \ 2020
Global Change Biology 26 (2020)2. - ISSN 1354-1013 - p. 888 - 900.
ammonia emissions - crop yield - fertilizers - greenhouse gases - livestock manure - meta-analysis - soil type - trade-offs
Recycling of livestock manure to agricultural land may reduce the use of synthetic fertilizer and thereby enhance the sustainability of food production. However, the effects of substitution of fertilizer by manure on crop yield, nitrogen use efficiency (NUE), and emissions of ammonia (NH3), nitrous oxide (N2O) and methane (CH4) as function of soil and manure properties, experimental duration and application strategies have not been quantified systematically and convincingly yet. Here, we present a meta-analysis of these effects using results of 143 published studies in China. Results indicate that the partial substitution of synthetic fertilizers by manure significantly increased the yield by 6.6% and 3.3% for upland crop and paddy rice, respectively, but full substitution significantly decreased yields (by 9.6% and 4.1%). The response of crop yields to manure substitution varied with soil pH and experimental durations, with relatively large positive responses in acidic soils and long-term experiments. NUE increased significantly at a moderate ratio (<40%) of substitution. NH3 emissions were significantly lower with full substitution (62%–77%), but not with partial substitution. Emissions of CH4 from paddy rice significantly increased with substitution ratio (SR), and varied by application rates and manure types, but N2O emissions decreased. The SR did not significantly influence N2O emissions from upland soils, and a relative scarcity of data on certain manure characteristic was found to hamper identification of the mechanisms. We derived overall mean N2O emission factors (EF) of 0.56% and 0.17%, as well as NH3 EFs of 11.1% and 6.5% for the manure N applied to upland and paddy soils, respectively. Our study shows that partial substitution of fertilizer by manure can increase crop yields, and decrease emissions of NH3 and N2O, but depending on site-specific conditions. Manure addition to paddy rice soils is recommended only if abatement strategies for CH4 emissions are also implemented.
Inorganic nitrogen deposition in China's forests: Status and characteristics
Du, E. ; Jiang, Y. ; Fang, J. ; Vries, W. de - \ 2014
Atmospheric Environment 98 (2014). - ISSN 1352-2310 - p. 474 - 482.
atmospheric deposition - canopy uptake - throughfall measurements - ammonia emissions - reduced nitrogen - bulk deposition - wet deposition - air-pollution - higher-plants - transport
Nitrogen (N) deposition in China has been dramatically enhanced by anthropogenic emissions and has aroused great concerns of its impacts on forest ecosystems. This study synthesized data on ammonium (NH4+) and nitrate (NO3-) contents in bulk precipitation and throughfall from 38 forest stands in published literature to assess the status and characteristics of N deposition to typical forests in China between 1995 and 2010. Our results showed that ammonium dominated N deposition in this period, with a mean NH4+–N:NO3-–N ratio of ~2.5 in bulk deposition and throughfall. Mean throughfall N deposition in China's forests was as high as 14.0 kg N ha-1 yr-1 for ammonium, 5.5 kg N ha-1 yr-1 for nitrate and 21.5 kg N ha-1 yr-1 for total inorganic N (TIN), respectively. Mean bulk deposition was 9.4 kg N ha-1 yr-1 for ammonium, 3.9 kg N ha-1 yr-1 for nitrate and 14.0 kg N ha-1 yr-1 for TIN, respectively. Canopy captured dry deposition, calculated as the difference between throughfall and bulk deposition, was thus approximately half of the bulk deposition. Spatial patterns of N deposition were in accordance with our urban hotspot hypothesis, showing a strong power-law reduction of ammonium with increasing distance to large cities but only slightly lower nitrate deposition. Our results suggest that high N deposition, especially of ammonium, exceeds critical N loads for large areas of China's forests.
Changes in wet nitrogen deposition in the United States between 1985 and 2012
Du, E. ; Vries, W. de; Galloway, J.N. ; Hu, X. ; Fang, J. - \ 2014
Environmental Research Letters 9 (2014). - ISSN 1748-9326 - 8 p.
precipitation chemistry - ammonia emissions - reactive nitrogen - reduced nitrogen - critical loads - trends - environment - future - usa
The United States (US) is among the global hotspots of nitrogen (N) deposition and assessing the temporal trends of wet N deposition is relevant to quantify the effectiveness of existing N regulation policies and its consequent environmental effects. This study analyzed changes in observed wet deposition of dissolved inorganic N (DIN = ammonium + nitrate) in the US between 1985 and 2012 by applying a Mann–Kendall test and Regional Kendall test. Current wet DIN deposition (2011–2012) data were used to gain insight in the current pattern of N deposition. Wet DIN deposition generally decreased going from Midwest > Northeast > South > West region with a national mean rate of 3.5 kg N ha-1 yr-1. Ammonium dominated wet DIN deposition in the Midwest, South and West regions, whereas nitrate and ammonium both contributed a half in the Northeast region. Wet DIN deposition showed no significant change at the national scale between 1985 and 2012, but profound changes occurred in its components. Wet ammonium deposition showed a significant increasing trend at national scale (0.013 kg N ha-1 yr-2), with the highest increase in the Midwest and eastern part of the South region. Inversely, wet nitrate deposition decreased significantly at national scale (-0.014 kg N ha-1 yr-2), with the largest reduction in the Northeast region. Overall, ratios of ammonium versus nitrate in wet deposition showed a significant increase in all the four regions, resulting in a transition of the dominant N species from nitrate to ammonium. Distinct magnitudes, trends and patterns of wet ammonium and nitrate deposition suggest the needs to control N emissions by species and regions to avoid negative effects of N deposition on ecosystem health and function in the US.
Potential of life cycle assessment to support environmental decision making at commercial dairy farms
Meul, M. ; Middelaar, C.E. van; Boer, I.J.M. de; Passel, S. van; Fremaut, D. ; Haesaert, G. - \ 2014
Agricultural Systems 131 (2014). - ISSN 0308-521X - p. 105 - 115.
greenhouse-gas emissions - organic milk-production - carbon footprint - ammonia emissions - systems - model - management - sustainability - indicators - impact
In this paper, we evaluate the potential of life cycle assessment (LCA) to support environmental decision making at commercial dairy farms. To achieve this, we follow a four-step method that allows converting environmental assessment results using LCA into case-specific advice for farmers. This is illustrated in a case-study involving 20 specialized Flemish dairy farms. Calculated LCA indicators are normalized into scores between 0 and 100, whereby a score of 100 is assumed optimal, to allow for a mutual comparison of indicators for different environmental impact categories. Next, major farm and management characteristics affecting environmental performance are identified using multiple regression and correlation analyses. Finally, comparing specific farm and management characteristics with those of best performing farms identifies farm-specific optimization strategies. We conclude that this approach complies with most of the identified critical success factors for the successful implementation of LCA as a decision support system for farmers. Key aspects herein are (i) the flexibility and accessibility of the model, (ii) the use of readily available farm data, (iii) farm advisors being intended model users, (iv) the identification of key farm and management characteristics affecting environmental performance and (v) the organization of discussion sessions involving farmers and farm advisors. However, attention should be paid (i) to provide sufficient training and guidance for farm advisors on the use of the applied LCA model and the interpretation of results, (ii) to evaluate the correctness of the used data and (iii) to keep the model up-to-date according to new scientific insights and knowledge concerning LCA methodology. Keywords Life cycle assessment; Dairy farms; Decision support system; MOTIFS
Mitigation of methane and nitrous oxide emissions from animal operations: II. A review of manure management mitigation options
Montes, F. ; Meinen, R. ; Dell, C. ; Rotz, A. ; Hristov, A.N. ; Oh, J. ; Waghorn, G. ; Gerber, P.J. ; Henderson, B.L. ; Makkar, H.P.S. ; Dijkstra, J. - \ 2013
Journal of Animal Science 91 (2013)11. - ISSN 0021-8812 - p. 5070 - 5094.
greenhouse-gas emissions - dietary crude protein - lactating dairy-cows - environmental systems-analysis - organic-carbon sequestration - phase compost biofilters - swine manure - ammonia emissions - anaerobic-digestion - cattle slurry
This review analyzes published data on manure management practices used to mitigate methane (CH4) and nitrous oxide (N2O) emissions from animal operations. Reducing excreted nitrogen (N) and degradable organic carbon (C) by diet manipulation to improve the balance of nutrient inputs with production is an effective practice to reduce CH4 and N2O emissions. Most CH4 is produced during manure storage; therefore, reducing storage time, lowering manure temperature by storing it outside during colder seasons, and capturing and combusting the CH4 produced during storage are effective practices to reduce CH4 emission. Anaerobic digestion with combustion of the gas produced is effective in reducing CH4 emission and organic C content of manure; this increases readily available C and N for microbial processes creating little CH4 and increased N2O emissions following land application. Nitrous oxide emission occurs following land application as a byproduct of nitrification and dentrification processes in the soil, but these processes may also occur in compost, biofilter materials, and permeable storage covers. These microbial processes depend on temperature, moisture content, availability of easily degradable organic C, and oxidation status of the environment, which make N2O emissions and mitigation results highly variable. Managing the fate of ammoniacal N is essential to the success of N2O and CH4 mitigation because ammonia is an important component in the cycling of N through manure, soil, crops, and animal feeds. Manure application techniques such as subsurface injection reduce ammonia and CH4 emissions but can result in increased N2O emissions. Injection works well when combined with anaerobic digestion and solids separation by improving infiltration. Additives such as urease and nitrification inhibitors that inhibit microbial processes have mixed results but are generally effective in controlling N2O emission from intensive grazing systems. Matching plant nutrient requirements with manure fertilization, managing grazing intensity, and using cover crops are effective practices to increase plant N uptake and reduce N2O emissions. Due to system interactions, mitigation practices that reduce emissions in one stage of the manure management process may increase emissions elsewhere, so mitigation practices must be evaluated at the whole farm level.
Interaction between dietary content of protein and sodium chloride on milk urea concentration, urinary urea excretion, renal recycling of urea, and urea transfer to the gastrointestinal tract in dairy cows
Spek, J.W. ; Bannink, A. ; Gort, G. ; Hendriks, W.H. ; Dijkstra, J. - \ 2013
Journal of Dairy Science 96 (2013)9. - ISSN 0022-0302 - p. 5734 - 5745.
fed grass-silage - ammonia emissions - nitrogen-excretion - holstein cows - cattle - metabolism - sheep - rumen - plasma - degradability
Dietary protein and salt affect the concentration of milk urea nitrogen (MUN; mg of N/dL) and the relationship between MUN and excretion of urea nitrogen in urine (UUN; g of N/d) of dairy cattle. The aim of the present study was to examine the effects of dietary protein and sodium chloride (NaCl) intake separately, and their interaction, on MUN and UUN, on the relationship between UUN and MUN, on renal recycling of urea, and on urea transfer to the gastrointestinal tract. Twelve second-parity cows (body weight of 645±37kg, 146±29d in milk, and a milk production of 34.0±3.28kg/d), of which 8 were previously fitted with a rumen cannula, were fitted with catheters in the urine bladder and jugular vein. The experiment had a split-plot arrangement with dietary crude protein (CP) content as the main plot factor [116 and 154g of CP/kg of dry matter (DM)] and dietary NaCl content as the subplot factor (3.1 and 13.5g of Na/kg of DM). Cows were fed at 95% of the average ad libitum feed intake of cows receiving the low protein diets. Average MUN and UUN were, respectively, 3.90mg of N/dL and 45g of N/d higher for the high protein diets compared with the low protein diets. Compared with the low NaCl diets, MUN was, on average, 1.74mg of N/dL lower for the high NaCl diets, whereas UUN was unaffected. We found no interaction between dietary content of protein and NaCl on performance characteristics or on MUN, UUN, urine production, and renal clearance characteristics. The creatinine clearance rate was not affected by dietary content of protein and NaCl. Urea transfer to the gastrointestinal tract, expressed as a fraction of plasma urea entry rate, was negatively related to dietary protein, whereas it was not affected by dietary NaCl content. We found no interaction between dietary protein and NaCl content on plasma urea entry rate and gastrointestinal urea entry rate or their ratio. The relationship between MUN and UUN was significantly affected by the class variable dietary NaCl content: UUN=-17.7±7.24 + 10.09±1.016 × MUN + 2.26±0.729 × MUN (for high NaCl); R(2)=0.85. Removal of the MUN × NaCl interaction term lowered the coefficient of determination from 0.85 to 0.77. In conclusion, dietary protein content is positively related to MUN and UUN, whereas dietary NaCl content is negatively correlated to MUN but NaCl content is not related to UUN. We found no interaction between dietary protein and NaCl content on performance, MUN, UUN, or renal urea recycling, nor on plasma urea entry rate and urea transfer to the gastrointestinal tract. For a proper interpretation of the relationship between MUN and UUN, the effect of dietary NaCl should be taken into account, but we found no evidence that the effect of dietary NaCl on MUN is dependent on dietary protein content.
Effect of sodium chloride intake on urine volume, urinary urea excretion, and milk urea concentration in lactating dairy cattle
Spek, J.W. ; Bannink, A. ; Gort, G. ; Hendriks, W.H. ; Dijkstra, J. - \ 2012
Journal of Dairy Science 95 (2012)12. - ISSN 0022-0302 - p. 7288 - 7298.
nitrogen-excretion - ammonia emissions - water restriction - renal-function - cows - sheep - metabolism - protein - agriculture - potassium
Milk urea nitrogen (MUN; mg of N/dL) has been shown to be related to excretion of urinary urea N (UUN; g of N/d) and total excretion of urinary N (UN; g of N/d) in dairy cows. In the present experiment, it was hypothesized that MUN and the relationship between MUN and UUN or UN is affected by urine volume as a result of dietary sodium chloride intake. Twelve lactating Holstein-Friesian dairy cows (mean ± SD: milk production 28.1 ± 3.23 kg/d and 190 ± 41 d in milk), of which 4 were fitted with catheters in the urine bladder and jugular vein, were randomly assigned to 4 dietary levels of sodium chloride (3, 9, 14, and 19 g of Na/kg of DM) according to a triple 4 × 4 Latin square design. Cows were fed at 95% of ad libitum intake, excluding salt addition. Milk was analyzed for MUN and protein content; urine was analyzed for total N, urea, and creatinine content; feces were analyzed for total N and DM content; and blood plasma was analyzed for urea and creatinine content. Creatinine clearance rate (CCR; L/min) and renal urea reabsorption ratio were estimated based on plasma concentrations of urea and creatinine, and total excretion of urea and creatinine in urine. Intake of DM and N, milk production, and milk protein content were (mean ± SD), on average, 21.4 ± 1.24 kg/d, 522 ± 32.0 g/d, 25.4 ± 2.53 kg/d, and 3.64 ± 0.186%, respectively. A linear relationship was found between Na intake and urine production [urine (kg/d; mean ± SE) = 7.5 ± 4.33 + 0.136 ± 0.0143 × Na intake (g/d)] and between Na intake and MUN [MUN (mg/dL; mean ± SE) = 13.5 ± 0.35 - 0.0068 ± 0.00104 × Na intake (g/d)]. Despite the decrease in MUN with increased Na intake, UN excretion increased linearly with Na intake. Excretion of UUN was not affected by dietary Na content. A linear plateau relationship was observed between CCR and renal urea reabsorption. An increase in CCR coincided with an increase in calculated renal urea reabsorption until a CCR breakpoint value (mean ± SD) of 1.56 ± 0.063 L/min was reached. We conclude that Na intake is negatively related to MUN, whereas UUN is not affected. Variation in mineral intake levels that affect urine volume should, therefore, be taken into account when using MUN as an indicator of UUN in dairy cattle.
Emission factors for methane and nitrous oxide from manure management and mitigation options
Groenestein, C.M. ; Mosquera Losada, J. ; Sluis, S. van der - \ 2012
Journal of integrative Environmental Sciences 9 (2012)suppl. 1. - ISSN 1943-815X - p. 139 - 146.
ammonia emissions - netherlands - inventory - model
Under the United Nations Framework Convention on Climate Change (UNFCCC), the Kyoto-protocol is aimed at reducing the emission of greenhouse gases. Therefore, members report their greenhouse gas (GHG) emissions every year in a National Inventory Report (NIR). For agriculture the Netherlands identify three sources of GHG: enteric fermentation (methane), manure management (methane and nitrous oxide) and agricultural soils (nitrous oxide). The Dutch NIR reported that in 2009 23% of the agricultural GHG was caused by manure management. The methane-emission factors for manure management were assessed by a Tier 2 approach, the nitrous-oxide-emission factors were IPCC 2000-defaults. Between 2008 and 2010 an extensive measuring programme was carried out resulting in emission factors for housing systems of methane and nitrous oxide. Overall it appeared that emission factors of methane were higher than reported in the NIR, and emission factors of nitrous oxide were lower. This study investigates the consequence of those emission factors for the total emission of GHG from livestock housing and manure storage and the perspective of implementation of mitigation measures
Dust Reduction in Broiler Houses by Spraying Rapeseed Oil
Aarnink, A.J.A. ; Harn, J. van; Hattum, T.G. van; Zhao, Y. ; Ogink, N.W.M. - \ 2011
Transactions of the ASABE / American Society of Agricultural and Biological Engineers 54 (2011)4. - ISSN 2151-0032 - p. 1479 - 1489.
ammonia emissions - respiratory symptoms - particulate matter - lung-function - buildings - litter - us - pm2.5 - pm10
The effect of spraying rapeseed oil on the reduction of dust and ammonia concentrations and emissions, and on animal parameters was investigated in a dose-response study in a broiler house during three growing periods in four (round 1) or five rooms (rounds 2 and 3). The spraying rates varied per room, from 0 (control) to 24 mL oil m(-2) d(-1). Concentrations of PM10 and PM2.5 in incoming and outgoing air were measured. Production results (growth rate, feed intake, mortality rate) and foot-pad lesions were also determined. Regression analysis showed that a spraying rate of 6 mL oil m(-2) d(-1) reduced PM10 concentrations by 44% and PM10 emissions by 48%. At 24 mL oil m(-2) d(-1), the reduction was 82% for PM10 concentrations and 87% for PM10 emissions. For PM2.5, the lowest spraying rate of 6 mL oil m(-2) d(-1) was sufficient to reduce concentrations by 68% and emissions by 84%. The reduction achieved at higher spraying rates was not significantly greater. Emissions of PM10 and PM2.5 increased exponentially with the age of the broilers. A clear diurnal pattern was observed, with lower dust concentrations during the dark periods. Production results were unaffected by the spraying rate. A high rate of 24 mL oil m(-2) d(-1) increased the number and severity of foot-pad lesions. It is concluded that spraying rapeseed oil significantly reduces dust concentrations and emissions from broiler houses. To prevent adverse effects on broilers' foot-pad quality, it is recommended that the maximum rate should he 16 mL oil m(-2) d(-1).
Effectiveness of multi-stage scrubbers in reducing emissions of air pollutants from pig houses
Zhao, Y. ; Aarnink, A.J.A. ; Jong, M.C.M. de; Ogink, N.W.M. ; Groot Koerkamp, P.W.G. - \ 2011
Transactions of the ASABE / American Society of Agricultural and Biological Engineers 54 (2011)1. - ISSN 2151-0032 - p. 285 - 293.
livestock operations - bioaerosol samplers - ammonia emissions - efficiencies - microorganisms - transmission - buildings - reduction - aerosols - europe
Emissions of air pollutants from livestock houses may raise environmental problems and pose hazards to public health. They can be reduced by scrubbers installed at the air outlets of livestock houses. In this study, three multi-stage scrubbers were evaluated in terms of their effectiveness in reducing emissions of airborne dust, total bacteria, ammonia, and CO2 from pig houses in winter. The three multi-stage scrubbers were one double-stage scrubber (acid stage+ bio-filter), one double-stage scrubber (acid stage + bio-scrubber), and one triple-stage scrubber (water stage + acid stage + bio-filter). Results showed that these scrubbers reduced concentrations of PM10 by 61% to 93%, concentrations of PM2.5 by 47% to 90%, concentrations of airborne total bacteria by 46% to 85%, and concentrations of ammonia by 70% to 100%. Concentrations of CO2 were not affected. Most of the airborne bacteria emitted from the pig houses were larger than 3.3 µm (73% to 95%). The multi-stage scrubbers removed 53% to 92% of them, compared with -42% to 20% removal effectiveness of the bacteria in the size range of 0.65 to 3.3 µm. The triple-stage scrubber was the most efficient in removing dust and ammonia. Compared to single-stage scrubbers, all three multi-stage scrubbers performed more consistently in reduction of PM10, PM2.5, total bacteria, and ammonia emissions from livestock houses and removed these pollutants more efficiently. It should be noted that all measurements were performed in winter at low ventilation rates, thus at low loadings of the multi-stage scrubbers
A whole-farm strategy to reduce environmental impacts of Nitrogen
Sonneveld, M.P.W. ; Schröder, J.J. ; Vos, J.A. de; Monteny, G.J. ; Mosquera, J. ; Hol, J.M.G. ; Lantinga, E.A. ; Verhoeven, F.P.M. ; Bouma, J. - \ 2008
Journal of Environmental Quality 37 (2008)1. - ISSN 0047-2425 - p. 186 - 195.
ammonia emissions - surface-water - peat soil - netherlands - losses - cattle - slurry
Dutch regulations for ammonia emission require farmers to inject slurry into the soil (shallow) or to apply it in narrow bands at the surface. For one commercial dairy farm in the Netherlands it was hypothesized that its alternative farming strategy, including low-protein feeding and surface spreading, could be an equally effective tool for ammonia emission abatement. The overall objective of the research was to investigate how management at this farm is related to nitrogen (N) losses to the environment, including groundwater and surface water. Gaseous emission of ammonia and greenhouse gasses from the naturally ventilated stables were 8.1 and 3.1 kg yr(-1)AU(-1) on average using the internal tracer (SF6)-ratio method. Measurements on volatilization of ammonia from slurry application to the field using an integrated horizontal flux method and the micrometeorological mass balance method yielded relatively low values of ammonia emissions per ha (3.5-10.9 kg NH3-N ha(-1)). The mean nitrate concentration in the upper ground water was 6.7 mg L-1 for 2004 and 3.0 mg L-1 for 2005, and the half-year summer means of N in surface water were 2.3 mg N L-1 and 3.4 mg N L-1 for 2004 and 2005, respectively. Using a nutrient budget model for this farm, partly based on these findings, it was found that the calculated ammonia loss per con milk (range 5.3-7.5 kg N Mg-1) is comparable with the estimated ammonia loss of a conventional farm that applies animal slurry using prescribed technologies.
Evaluation of methods for quantifying agricultural emissions of air, water and soil pollutants
Havlikova, M. ; Kroeze, C. - \ 2006
Science of the Total Environment 372 (2006)1. - ISSN 0048-9697 - p. 133 - 147.
nitrous-oxide emissions - ammonia emissions - gas emissions - model - europe - temperate
Integrated assessments that analyze global warming, acidification, eutrophication and ozone related problems simultaneously, need complete, detailed and consistent emission estimates that consider possible interrelations between different pollutants. We discuss three types of emission estimation methods: emission factor, regression analyses and process-based methods. Selected examples of these are reviewed to illustrate the large variety in methods available. We present an approach for the evaluation of emission estimation methods which follows three steps: (1) Comparison, (2) Scoring and (3) Multi-Criteria Analysis (MCA). We demonstrate the usefulness of this approach by applying it to a case study for the Czech Republic. Firstly we compare selected methods with respect to characteristics which we consider as requirements to quantify emissions of air, water and soil pollutants in an integrated way. We observe that none of the selected methods fully meet our defined characteristics. Secondly, we score the methods with respect to three types of criteria. This evaluation reveals large differences between the methods. We conclude that the following methods best meet our criteria: the IPCC Guidelines, methods from INITIATOR, and the detailed method of the EMEP/CORINAIR Guidebook. Finally, we perform a Multi-Criteria Analysis to analyze how our conclusions change if one considers certain criteria as more important than others. Based on this analysis we suggest that combining parts of each of the three methods forms a sound basis for a new emission estimation method for quantifying agricultural emissions of air, water and soil pollution simultaneously
Nitrogen cycling efficiencies through resource-poor African crop-livestock systems
Rufino, M.C. ; Rowe, E.C. ; Delve, R.J. ; Giller, K.E. - \ 2006
Agriculture, Ecosystems and Environment 112 (2006)4. - ISSN 0167-8809 - p. 261 - 282.
soil fertility management - quality native hay - farming systems - cattle manure - organic-matter - dairy-cows - ammonia emissions - sesbania-sesban - milk-production - nutrient-uptake
Success in long-term agricultural production in resource-poor farming systems relies on the efficiency with which nutrients are conserved and recycled. Each transfer of nutrients across the farming system provides a risk of inefficiency, and how much is lost at each step depends on the type of farming system, its management practices and site conditions. The aim of this review was to identify critical steps where efficiency of nitrogen (N) cycling through livestock in smallholder crop-livestock farming systems could be increased, with special emphasis on Africa. Farming systems were conceptualised in four sub-systems through which nutrient transfer takes place: (1) livestock: animals partition dietary intake into growth and milk production, faeces and urine; (2) manure collection and handling: housing and management determine what proportion of the animal excreta may be collected; (3) manure storage: manure can be composted with or without addition of plant materials and (4) soil and crop conversion: a proportion of the N in organic materials applied to soil becomes available, part of which is taken up by plants, of which a further proportion is partitioned into grain N. An exhaustive literature review showed that partial efficiencies have been much more commonly calculated for the first and last steps than for manure handling and storage. Partial N cycling efficiencies were calculated for every sub-system as the ratio of nutrient output to nutrient input. Estimates of partial N cycling efficiency (NCE) for each sub-system ranged from 46 to 121% (livestock), 6 to 99% (manure handling), 30 to 87% (manure storage) and 3 to 76% (soil and crop conversion). Overall N cycling efficiency is the product of the partial efficiencies at each of the steps through which N passes. Direct application of plant materials to soil results in more efficient cycling of N, with fewer losses than from materials fed to livestock. However, livestock provide many other benefits highly valued by farmers, and animal manures can contain large amounts of available N, which increases the immediate crop response. Manures also can contribute to increase (or at least maintain) the soil organic C pool but more quantitative information is needed to assess the actual benefits. Making most efficient use of animal manures depends critically on improving manure handling and storage, and on synchrony of mineralisation with crop uptake. Measures to improve manure handling and storage are generally easier to design and implement than measures to improve crop recovery of N, and should receive much greater attention if overall system NCE is to be improved.
Identifying sustainability issues using participatory SWOT analysis - A case study of egg production in the Netherlands
Mollenhorst, H. ; Boer, I.J.M. de - \ 2004
Outlook on Agriculture 33 (2004)4. - ISSN 0030-7270 - p. 267 - 276.
ammonia emissions - housing systems - quality - america - cages
The aim of this paper was to demonstrate how participatory strengths, weaknesses, opportunities and threats (SWOT) analysis can be used to identify relevant economic, ecological and societal (EES) issues for the assessment of sustainable development. This is illustrated by the case of egg production in the Netherlands. Participatory methods are used to facilitate the exchange of ideas, experiences and knowledge of all relevant stakeholders and to create a basis for implementation of the final results. It can be concluded that the combination of a brainstorming session and SWOT analysis with a heterogeneous group of stakeholders constitutes a useful tool to order and structure these listed aspects and to identify relevant issues for sustainable development. Final selection of EES issues from the SWOT analysis, however, required additional reviewing of the literature and consultation with experts from specific fields. Final EES issues selected in the case study of Dutch egg production include welfare and health, environment, quality, ergonomics, economics, consumer concerns, and knowledge and innovation