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.
Highlights
No-tillage system is efficient in reducing soil losses caused by rainfall erosion, when compared to the conventional tillage (Cogo, 1981; Bertol, 1995)
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
Summary
No-tillage system is efficient in reducing soil losses caused by rainfall erosion, when compared to the conventional tillage (Cogo, 1981; Bertol, 1995). These effects are generally lower on water, and chemical and organic elements losses (Schick et al, 2000; Bertol et al, 2003). The no-tillage system produces lower water and sediments losses by rainfall erosion than conventional tillage (Cogo, 1981; Bertol, 1995), while runoff of conventional tillage usually concentrates less plant nutrients and. Sometimes calcium and magnesium concentrations are higher in runoff sediments than in superficial soil layer (Stoltenberg & White, 1953); in other conditions an inverse behavior would be observed (Schick et al, 2000)
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