Abstract:The no-tillage cropping system, a combination of ancient and modern agricultural practices, has been rapidly increasing in use. By the year 2000, as much as 65 percent of the acreage of crops grown in the United States may be grown by the no-tillage practice. Soil erosion, the major source of pollutants in rural streams, is virtually eliminated when no-tillage agriculture is practiced. The no-tillage system reduces the energy input into corn and soybean production by 7 and 18 percent, respectively, when compar… Show more
“…In the mid-20th century, recognition that conventional agriculture dramatically accelerated soil erosion led to experimentation with conservation tillage and no-till agriculture (40,41). Over the past several decades, no-till agriculture has been increasingly adopted as a cost-effective alternative to conventional tillage practices.…”
Data drawn from a global compilation of studies quantitatively confirm the long-articulated contention that erosion rates from conventionally plowed agricultural fields average 1-2 orders of magnitude greater than rates of soil production, erosion under native vegetation, and long-term geological erosion. The general equivalence of the latter indicates that, considered globally, hillslope soil production and erosion evolve to balance geologic and climate forcing, whereas conventional plow-based agriculture increases erosion rates enough to prove unsustainable. In contrast to how net soil erosion rates in conventionally plowed fields (Ϸ1 mm/yr) can erode through a typical hillslope soil profile over time scales comparable to the longevity of major civilizations, no-till agriculture produces erosion rates much closer to soil production rates and therefore could provide a foundation for sustainable agriculture.agriculture ͉ civilization
“…In the mid-20th century, recognition that conventional agriculture dramatically accelerated soil erosion led to experimentation with conservation tillage and no-till agriculture (40,41). Over the past several decades, no-till agriculture has been increasingly adopted as a cost-effective alternative to conventional tillage practices.…”
Data drawn from a global compilation of studies quantitatively confirm the long-articulated contention that erosion rates from conventionally plowed agricultural fields average 1-2 orders of magnitude greater than rates of soil production, erosion under native vegetation, and long-term geological erosion. The general equivalence of the latter indicates that, considered globally, hillslope soil production and erosion evolve to balance geologic and climate forcing, whereas conventional plow-based agriculture increases erosion rates enough to prove unsustainable. In contrast to how net soil erosion rates in conventionally plowed fields (Ϸ1 mm/yr) can erode through a typical hillslope soil profile over time scales comparable to the longevity of major civilizations, no-till agriculture produces erosion rates much closer to soil production rates and therefore could provide a foundation for sustainable agriculture.agriculture ͉ civilization
“…This is crucial for designing landscapes and management practices that optimize trade-offs -and tradeoffs are unavoidable. For example, no-till soil management builds soil organic matter and adds trophic complexity to crop fields, but requires chemical weed control (Phillips et al 1980). Bt corn, genetically modified to express Bacillus thuringiensis (Bt) insecticidal proteins that confer resistance to European corn borers, reduces the need for insecticidal sprays, but may affect other lepidopterans as well (Pimentel and Raven 2000).…”
“…Nos primeiros anos de plantio direto, é comum verificar menor disponibilidade de N às plantas quando comparado ao preparo convencional (Phillips et al, 1980;Blevins et al, 1983;Freitas, 1988;Rosso, 1989;Sá, 1992). Várias são as razões atribuídas a este fato: maior imobilização, menor mineralização, recuperação do estoque de MO, dentre outras.…”
Section: Nitrogênio Total No Solo E Mineralizaçãounclassified
RESUMOO nitrogênio, na maioria das situações, é o nutriente que mais influencia o rendimento do milho. O manejo da adubação nitrogenada deve satisfazer o requerimento da cultura com o mínimo de risco ambiental. Para tanto, é necessário que a recomendação da dose de adubo nitrogenado seja a mais exata possível. A generalização do uso do sistema de plantio direto e culturas de cobertura, no Sul do Brasil, criou a necessidade de ser a recomendação da adubação nitrogenada adaptada a este novo cenário agrícola. O presente trabalho, além de considerar o teor de MO e a expectativa do rendimento de grãos de milho na recomendação da adubação nitrogenada conforme preconiza a CFS-RS/SC (1995), propõe a introdução de um terceiro parâmetro que é a contribuição em N das culturas de cobertura antecedente. O efeito das culturas de cobertura foi considerado em três situações: leguminosas em cultivo solteiro, gramíneas em cultivo solteiro e consorciações. No caso de leguminosas e gramíneas em cultivo solteiro, a influência na disponibilidade de N foi considerada com base na produção de matéria seca, enquanto, nas consorciações, a proporção da leguminosa foi o principal fator considerado. A recomendação de adubação apresentada neste trabalho não dispensa acompanhamento de campo, visando a ajustes que se fizerem necessários, especialmente porque sistemas de produção, baseados em culturas de cobertura, dependem de processos biológicos influenciados por condições de clima, manejo e solo, que devem ser acompanhados localmente.Termos de indexação: fertilidade do solo, adubos verdes, decomposição de resíduos, Zea mays.
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