Until the 1950s most fanning was carried out on smaller family farms that used organic fertilizers and essentially their waste production was easily assimilated by soils and receiving water bodies. The period post 1950 has seen a worldwide shift to larger monoculture], intensively operated farm units. The farm yields have increased dramatically, however, to sustain the increasing yields and productivity farms are using large quantities of chemical fertilizers and pesticides. At the same time,

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... forestation has occurred on a large scale since the 1950s and the deforested land has been converted to agricultural (mostly in developing countries) and urban (both developed and undeveloped countries) land uses. Also, a massive shift of population from rural areas to the cities has occurred in developing countries since the 1950s. Surface and groundwater quality degradation due to agricultural practices and conversion of land to agriculture can be categorized as follows: a) degradation due to land use conversion from native lands to agriculture; b) increased erosion and soil loss due to agricultural practices; c) chemical pollution by fertilizers and pesticides; and d) pollution from animal operations. Abatement of agricultural diffuse sources of pollution can and must be conducted in the context of moving toward sustainable agriculture. Some trends toward sustainable agriculture are already emerging in the US and Europe.