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61.
É.G. Castanheira 《Agricultural Systems》2010,103(7):498-507
The activities associated with raw milk production on dairy farms require an effective evaluation of their environmental impact. The present study evaluates the global environmental impacts associated with milk production on dairy farms in Portugal and identifies the processes that have the greatest environmental impact by using life cycle assessment (LCA) methodology. The main factors involved in milk production were included, namely: the dairy farm, maize silage, ryegrass silage, straw, concentrates, diesel and electricity. The results suggest that the major source of air and water emissions in the life cycle of milk is the production of concentrates. The activities carried out on dairy farms were the major source of nitrous oxides (from fuel combustion), ammonia, and methane (from manure management and enteric fermentation). Nevertheless, dairy farm activities, which include manure management, enteric fermentation and diesel consumption, make the greatest contributions to the categories of impact considered, with the exception of the abiotic depletion category, contributing to over 70% of the total global warming potential (1021.3 kg CO2 eq. per tonne of milk), 84% of the total photochemical oxidation potential (0.2 kg C2H4 eq. per tonne of milk), 70% of the total acidification potential (20.4 kg SO2 eq. per tonne of milk), and 41% of the total eutrophication potential (7.1 kg eq. per tonne of milk). The production of concentrates and maize silage are the major contributors to the abiotic depletion category, accounting for 35% and 28%, respectively, of the overall abiotic depletion potential (1.4 Sb eq. per tonne of milk). Based on this LCA case study, we recommend further work to evaluate some possible opportunities to improve the environmental performance of Portuguese milk production, namely: (i) implementing integrated solutions for manure recovery/treatment (e.g. anaerobic digestion) before its application to the soil as organic fertiliser during maize and ryegrass production; (ii) improving manure nutrient use efficiency in order to decrease the importation of nutrients; (iii) diversifying feeding crops, as the dependence on two annual forage crops is expected to lead to excessive soil mobilisation (and related impacts) and to insignificant carbon dioxide sequestration from the atmosphere; and (iv) changing the concentrate mixtures. 相似文献
62.
Environmental service provision is increasingly discussed as a potential new venue for the simultaneous pursuit of development and natural resource conservation objectives, particularly among landowners in the low-income tropics. To date, most of the experience with such market-regulated mechanisms comes from water and forest projects in Latin America. Preliminary evidence suggests that participation of, and benefits to, small-scale land users are highly unequal and that the synergistic goals of poverty reduction and resource conservation through these emerging market mechanisms might be overly ambitious. This paper assesses the possibility of pro-poor environmental service provision through carbon sequestration among smallholders in the Sahel. It focuses on a case study in the small-scale, rain-fed agricultural systems of the Old Peanut Basin of Senegal. Based on a conceptual framework including economic, institutional, policy and livelihood factors, it assesses to the extent to which specific groups of farmers are able or willing to participate in and benefit from potential carbon offset programs. Finally, the paper stresses the need for adequate and equitable financial support and a careful rethinking of the institutional structures necessary to enhance rural livelihoods and natural resource management in drylands, with or without market-based environmental service programs. 相似文献
63.
Evaluating a multi-level subsurface drainage system for improved drainage water quality 总被引:1,自引:0,他引:1
This paper describes a multi-level drainage system, designed to improve drainage water quality. Results are presented from a field scale land reclamation experiment implemented in the Murrumbidgee Irrigation Area of New South Wales, Australia. A traditional single level drainage system and a multi-level drainage system were compared in the experiment in an irrigated field setting. The single level drainage system consisted of 1.8 m deep drains at 20 m spacing. This configuration is typical of subsurface drainage system design used in the area. The multi-level drainage system consisted of shallow closely spaced drains (3.3 m spacing at 0.75 m depth) underlain by deeper widely spaced drains (20 m spacing at 1.8 m depth). Data on drainage flows and salinity, water table regime and soil salinity were collected over a 2-year period. 相似文献
64.
Tracey Jones Ruth Feber Gabriel Hemery Paul Cook Katy James Curt Lamberth Marian Dawkins 《Agricultural Systems》2007
The commercial, welfare and environmental impacts of rearing small colonies of free-range chickens in newly planted woodland at two sites in the UK, during the first 2 years of the enterprise, were investigated. Newly planted rather than established trees were used so that commercially viable species could be planted in a way that would suit the management of the chicken enterprise, and small colonies were used so that farmers wishing to diversify could buy into the system progressively. It was anticipated that marketing a high specification product would provide an immediate income, whilst waiting for the future investment in trees to grow. 相似文献
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不同有机酸对小白菜镉污染毒性和品质的影响 总被引:1,自引:0,他引:1
以小白菜为试材,以贵州典型黄壤为盆栽试验基质,在黄土中共设置5个不同处理,1)原始无污染土壤(CK);2)单一镉污染土壤处理(Cd);3)镉污染土壤加草酸处理(Cd+OA);4)镉污染土壤加柠檬酸处理(Cd+CA);5)镉污染土壤加酒石酸处理(Cd+TA),探究镉胁迫下不同有机酸对提高小白菜品质的效果,以期为改善蔬菜品质提供参考依据。结果表明:外源添加镉导致小白菜单株鲜质量降低了41.1%,植株体内镉大量积累,活性氧类物质、丙二醛(MDA)和脯氨酸含量升高。与对照组相比,镉污染小白菜叶片内硝酸盐含量增加了2.9倍,维生素C和可溶性糖含量分别降低了19.3%和9.9%。在镉污染土壤上施入草酸、柠檬酸和酒石酸后均显著改善了小白菜的生长状态。与镉污染处理小白菜相比,柠檬酸对小白菜的促生效果最显著,生物量相对增加了48.5%,叶片和根的镉含量分别降低了45.3%和42.6%。酒石酸对超氧阴离子的影响大于草酸和柠檬酸,对过氧化氢和脯氨酸的影响小于草酸和柠檬酸,但草酸抑制硝酸盐积累和提高可溶性糖含量的作用大于其它有机酸。上述结果说明,在镉污染土壤施用柠檬酸可以有效缓解镉对小白菜的毒害作用,提高小白菜的产量和品质。 相似文献
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Gene How is a key concern associated with the eonlamination of seed multiplication iields and the use of transgenic crops. The release of herbicide-resistant germplasnis and the use of male-sterile varieties make foxtail millet (Sviaria ilalicii) an appropriate material to inves-tigate this concern. Pollen dispersal from pollen donor sources and gene tlow in fertile and male-slerile varieties of fortail millet were investigated in experiments in China and France. Although foxtail millel is mainly autogamous (less than 2% oiitcrossing), pollen from a 5m diameter plot could fertilize a tertile variety up to 24 ni away, and a male-sterile variety up to 40m. Negative exponential and WeibuU fnnctions were used to tit the relationships between percentage and number i.A iubrids per cm of ear with distance from the pollen source. Wind velocity and direction resulted in variations of gene How intensity, but did nol change liie slope ofthe regression equations. Pollen competition for available target ovules was observed up to 2 m away from a 1 m diameter pollen source. The percentage of pollen grains that fertilized ovules outside the pollen donor source was 1.4% of the total pollen grain produetion. For every iflO pollen grains released under lieid conditions 1.5 seeds were produced. The probability funetion of pollen dispersal for one donor plant was calculated. It allowed predictions of gene How accord-ing to lield shapes, estimations of isolation distances to preserve /ariety purity against pollen contamination, and the fornuiiation of efficient male/female ratios Ibr hybrid seed production. 相似文献