Soil tillage, water erosion, and calcium, magnesium and organic carbon losses

Abstract

Soil tillage influences water erosion, and consequently, losses of calcium, magnesium and organic carbon in surface runoff. Nutrients and organic carbon are transported by surface runoff in particulate form, adsorbed to soil colloids or soluble in water, depending on the soil tillage system. This study was carried out on an Inceptisol, representative of the Santa Catarina highlands, southern Brazil, between November 1999 and October 2001, under natural rainfall. The soil tillage treatments (no replications) were: no-tillage (NT), minimum soil tillage with chiseling + disking (MT), and conventional soil tillage with plowing + two diskings (CT). The crop cycles sequence was soybean (Glycine max), oats (Avena sativa), beans (Phaseolus vulgaris) and vetch (Vicia sativa). Conventional soil tillage treatment with plowing + two disking in the absence of crops (BS) was also studied. Calcium and magnesium concentrations were determined in both water and sediments of the surface runoff, while organic carbon was measured only in sediments. Calcium and magnesium concentrations were greater in sediments than in surface runoff, while total losses of these elements were greater in surface runoff than in sediments. The greatest calcium and magnesium concentrations in surface runoff were obtained under CT, while in sediments the greatest concentration occurred under MT. Organic carbon concentration in sediments did not differ under the different soil tillage systems, and the greatest total loss was under CT system. Key words: runoff, sediment, nutrient in runoff, nutrient in sediments, nutrient losses PREPARO DO SOLO, EROSÃO HÍDRICA, E PERDAS DE CÁLCIO, MAGNÉSIO E CARBONO ORGÂNICORESUMO: O preparo do solo influencia a erosão hídrica e, consequentemente, as perdas de cálcio, magnésio e carbono orgânico. Nutrientes e carbono orgânico são transportados na enxurrada superficial, podendo estar predominantemente adsorvidos aos colóides do solo ou solúveis na água, dependendo do sistema de preparo do solo. Este trabalho foi conduzido em um Inceptisol, representativo das terras de altitude de Santa Catarina, sul do Brasil, entre novembro de 1999 e outubro de 2001, sob chuva natural. Os tratamentos de preparo do solo, sem repetição, foram: semeadura direta (SD), preparo mínimo do solo com escarificação + gradagem (PM) e preparo convencional do solo com aração + duas gradagens (PC), com a seqüência dos cultivos de soja (Glycine max), aveia preta (Avena sativa), feijão (Phaseolus vulgaris) e ervilhaca comum (Vicia sativa). Um tratamento de preparo convenvional do solo com aração + duas gradagens na ausência de cultivo (SC) foi também estudado. Os conteúdos de cálcio e magnésio foram determinados na água e nos sedimentos da enxurrada superficial, enquanto o de carbono orgânico foi avaliado somente nos sedimentos. As concentrações de cálcio e magnésio foram maiores nos sedimentos do que na água da enxurrada superficial, enquanto as perdas totais desses elementos foram maiores na água do que nos sedimentos. As maiores concentrações ...

Tropical agriculture and global warming: impacts and mitigation options

“…Farming methods that use mechanical tillage, such as the mouldboard plough for seedbed preparation or discing for weed control, can promote soil C loss by several mechanisms: they disrupt soil aggregates, which protect soil organic matter from decomposition (Karlen & Cambardella, 1996;Six et al, 1999;Soares et al, 2005), they stimulate short-term microbial activity through enhanced aeration, resulting in increased levels of CO 2 and other gases released to the atmosphere (Bayer et al, 2000a;2000b;Kladivko, 2001), and they mix fresh residues into the soil where conditions for decomposition are often more favourable than on the surface (Karlen & Cambardella 1996;Plataforma Plantio Direto, 2006). Furthermore, tillage can leave soils more prone to erosion, resulting in further loss of soil C (Bertol et al, 2005;Lal, 2006).…”

“…Food production can suffer from climate change impacts such as alteration in solar radiation period and extreme weather events (IPCC, 2001;Overpeck & Cole, 2006). Secondly, the illegal and random deforestation reduces crop production by jeopardizing environmental services such as crop pollination, genetic resources, clean air and water supplies (Foley et al, 2005), soil fertility and erosion (Bertol et al, 2005), pests and pathogen controls that help to maintain crop production (Ghini & Morandi, 2006).…”

Liming and Ionic speciation of an Oxisol under no-till system

“…The better ero-sion control as compared to the conventional tillage system leads to smaller losses of organic carbon and nutrients, mainly Ca and Mg (Bertol et al, 2005). Consequently, the area under NT in Brazil has grown in the last few years.…”

Valuation and assessment of soil erosion costs

“…Bennett (1929Bennett ( , 1933Bennett ( , 1935Bennett ( , 1939Bennett ( , 1940Bennett ( , 1955, Pimentel et al (1995) and Uri (2000Uri ( , 2001 are among the leading researchers who have devoted time and effort to study the costs of on-site soil erosion (based on nutrient losses and drops in yield) and off-site soil erosion (based on off-site impacts). On-site costs can be calculated using the cost of nutrient replacement, associating the physical quantity of erosion associated with nutrient losses, normally macronutrients: calcium, phosphorus, magnesium, nitrogen and potassium (Amaral Sobrinho and Mazur, 2005;Adhikari and Nardella, 2011;Bertol et al, 2005Bertol et al, , 2007Gunatilake and Vieth, 2000;Marques et al, 1961;Pimentel et al, 1995;Pugliesi et al, 2011;Tengberg et al, 1997) calculated on the basis of market prices for commercial fertilizers and the quantity necessary to replace lost nutrients, plus the application cost. The calculations can be based on lost yield, i.e.…”