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AGR 2050 (2)

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AGR 2050
Clarence J Swanton

Agricultural sustainability and intensive production practices NOTES - Tilamen Article Introduction - modern ag. feeds 6 B people, global cereal has doubled in past 40 years - increased yeilds due to fertilizer, water, pesticides, “green revolution” technology - reduced global hunger, improved nutrition - global population projected to be 50% larder than present, grain demand doubled - projected 2.4 increase in per capita real income, dietary shift towards higher proportion of meat - CHALLENGE: - need increase in agricultural output essential for global political and social stability and equity - need to be done in way that doesn’t compromise environmental integrety, public health - article focuses on scientific and policy challanges Sustainability and net benefits - agriculturalists chief managers of terrestrial useable lands - 1/2 of global usable land is already in pastoral or intensive agriculture - in addition to loss of natural ecosystems ag. adds detremental amounts of nitrogen and phosphorus to terrestrial ecosystems at rates that may triple if past practices are used to double food production - costs typically unmeasured and often do not influence farmer/societal choices about production methods - sustainability definition: meet the current and future societal needs for food and fibre, for ecosystem services for healthy lives and that by doing so maximizes net benfit to society when all cost and benefits of practice are consid- ered - must be fuller accounting of both the costs and benefits of alternative ag practices - accounting must become the basis of policy, ethics, and action - accompanied by advances in sustainable energy use, mantufacturing, transportation and other economic sectors Ecosystem Services: -ecosystems provide food, fuel, fiber and other materials for selfter - provide other benefits hard to price - intact forests minimize flooding by slowing meltdown and water discharge, moderate regional climate, remove and store atmospheric carbon dioxide (GHG) - forest and grasslands, regenerate fertile soils, degrade plant liter and animal wastes, purify water - Essential for subsistence slash and burn farming - the recharge of streams by intact ecosystem provides possible water - Agriculture can reduce ability of the ecosystems to provide goods and services - for example high application of fertilizer and pesticides equals increase nutrients and toxins in groundwa- ter and surface water - high water purification costs - decreasing fishery and recreational values - agriculture agricultural practices that degrade soil quality contribute to eutrophication of aquatic habitats and may necessitate increased fertilization, irrigation, and energy to maintian productivity on degraded soils - practices that change species composition reduce biodiversity in non-agricultural systems diminished goods and services bc ability to provide services depend on the number and type of species Global Land Management - increase global food supply has inadvertent detrimental impacts on the environment and ecosystem services - Focus on cereal crops livestock and practices of more developed countries however sustainability articulated can be relevant to all countries - Costs and benefits of agricultural practices must be based on local values and local constraints therefore sustain- able practices to be region and culture specific - Accurate quantification of practices is necessary for identifying best options - Fundamental shifts in institutions policies and incentives will be required in the search for an broad adoption of sustainable agriculture practices and this must be an ongoing adaptive process Food Production and Environmental Costs - sustainability high-yield maintained even in the face of shocks with acceptable environmental impacts - The main environmental impact of agriculture come from the conversion of natural ecosystem to agriculture from agricultural nutrients that pollute aquatics and terrestrial habitats, groundwater and from pesticide especially bio ac- cumulating or persistent organic agriculture pollutants - Agricultural nutrients enter other ecosystems through leaching volatilization and waste streams of live- stock in humans - Pesticides and pathogens including antibiotic resistant pathogens can be harmful human health - how can these costs be minimized while food production increased? - Large increases in efficiency of nitrogen phosphorus and water use an integrated pest management that minimizes the need for toxic pesticides - Greatest scientific challenge facing humankind because of the trade-offs among competing economic and environmental goals and in adequate knowledge of key biological biochemical and ecological processes Increasing Yields -best quality farmland is already used for agriculture which means that further area expansion would occur on mar- ginal lands unlikely to sustain high-yield and vulnerable to degradation. - water limiting factor - In Asia rate of increase in rice yields is declining as actual crop approach a ceiling for maximum yield potential - Continuous cereal production systems including two or three crop per year may progressively become susceptible to diseases and insect pests because of insufficient diverse city in the crop rotation - average yields are currently about 80% of the climate adjusted genetic yeild potential ceiling - Lack of large exploitive yeild gap highlights the need for increased yeild potential ceiling - Large yeild gap for rice in many parts of South and South East Asia and for maize indicates that in these regions there could be significant yield increases with use of appropriate technologies - stagnant yield potential is one of the chief impediments the sustainable agriculture and concerted efforts are need- ed to increase the yield potential a major staple food crops Increasing Nutrient Use Efficiency - intensive high-yield agriculture is dependent on additional fertilizers especially industrial produced NH4 and NO3 - in some regions constraint by too little application of fert - Without the use of synthetic fertilizer world food production could not have increased at the rate he did and more natural ecosystems would of been converted to agriculture - Nitrogen and phosphorus expected to increase another threefold by 2050 unless there is a substantial increase in fertilizer deficiency - Fertilizer use and legume crops have almost doubled total annual nitrogen inputs to global terrestrial ecosystems - Phosphorus fertilizers have contributed to Doubling of annual terrestrial phosphorus mobilization globally - Further increases the nitrogen and phosphorous application are unlikely to be effective at increasing yields because of diminishing returns - Highest efficiency N fertilizer is achieved with her first increments of added N - At present only 30 to 50% of aplite nitrogen fertilizer and 45% of phosphorous fertilizer is taking up my crops - Nonpoint nutrient losses harm offsite ecosystems water quality and aquatic ecosystems and contribute to changes in atmospheric composition - over enrichment, eutrophication and low-oxygen conditions that endanger fisherys - Lost nitrogen contributes to Rievene input into the North Atlantic that is two to 20 times larger than in preindustrial times - nitrogen fertilization can increase emission gases that have critical roles in tropospheric and stratospheric chem- istry and air pollution - Nitrous oxides emitted from agricultural soils and through combustion increase trophosphoric ozone a component of smog that impacts human health agricultural crop and natural ecosystems - Can be transported atmospherically over long distances and deposited in terrestrial and aquatic ecosys- tems - Causes eutropification, loss of diversity, dominance by weedy species and increased nitrate leaching - nitrous oxide is GHG - Rice paddy agriculture and livestock production are most important anthropogenic sources of greenhouse gas methane - Solutions require nitrogen fertilizer efficiency - there are variety of practices that can contribute to increased efficiency for example large investments in the public sector research and extension education and investment by farmers and soil testing and im- prove timing of fertilizer application - Cover crops and reduce tillage can reduce leaching, volitilization and erosional losses of nutrients, in- creased efficiency - Closing the nitrogen and phosphorus cycles such as by appropriate application of livestock and human wastes increases cereal production per unit of synthetic fertilizer applied - slow release of nutrients from organic compost or green manuers must be investigated as a means to match de- mand with nutrient supply and increase nitrogen eficiency/ decrease leaching and volitilization in intensive produc- tion systems - N use eficiency is increased by matching temporal and spatial nutrient supply with plants demand - Applying fertilizer during periods of great crop demand at or near the plant roots and in smaller more fre- quent applications = precision agriculture - need appropriate diagnostic tools - Croprotations or intercropping may improve pest-control and increase nutrients and water efficiency - Agroforestry in which trees are including intercropping system - reduce erosion provide firewood and store car- bon - improve nutrient availability - Landscape scale management important - Individual farms watersheds and regional planning can take advantage of services provided by adjacent natural seminatural or restored ecosystems - Trees and shrubs planted in buffer strips surrounding cultivated field decrease soil erosion take out nutri- ents that would otherwise enter surface or ground waters - Buffer zones along streams rivers and lakeshores can decrease nutrient and silt loading from croplands - buffer zones can be managed to reduce inputs of weeds and pests - Pollination from insects and other little animals living in habitats or buffer strips - Other organisms such as parasitiods control many agricultural pests Increased Water-Use Efficiency - greater agricultural production will require increased irrigation unless water use efficiency is increased - However global rate of increase in irrigated area is declining and new dam construction may only allow for a 10% increase in water for irrigation over the next 30 years - Water is regionally scarce - Roughly 20% of the irrigated area of the United States is supplied by groundwater pumped in excess of recharge overcoming is a serious concern in China India and Bangladesh - Urban water use restoration of streams for recreational fish water fisheries and protection of natural ecosystems are all providing competition for water resources previously dedicated to agriculture - Irrigation return clothes typically carry more salt nutrients minerals and pesticides into surface and groundwater and source water impacting downstream agricultural national systems and drinking water - Technology such as drip and pivot irrigation can Inc. prove water use efficiency and decrease salinization while maintaining or increasing yields - But expanded use is currently not economically viable for staple food crops - in developing countries 15,000,000 ha have experience reduced yields owing to salt accumulation and waterlogging - the water holding capacity of soil can be increased by adding your already seen tillage and by other approaches that maintain or increa
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