Preparado do solo, erosao hídrica, e perdas de cálcio, magnésio e carbono orgânico

[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

Perdas de nutrientes na água da erosão hídrica

A erosão hídrica causa o empobrecimento dos solos, devido ao transporte de nutrientes, os quais são transportados tanto adsorvidos aos colóides do solo quanto solubilizados na água, podendo variar com o sistema de manejo solo. O trabalho foi conduzido em São José do Cerrito (SC), entre março de 2000 e junho de 2001, com o objetivo de quantificar as perdas de nitrogênio, fósforo, potássio, cálcio e magnésio na água da erosão hídrica sob chuva simulada, nos seguintes sistemas de manejo: aração+duas gradagens sem cultivo do solo (SSC), aração+duas gradagens com cultivo de soja (PCO), escarificação+uma gradagem com cultivo de soja (CMI), semeadura direta de soja em campo natural dessecado e queimado (SDDQ) e semeadura direta de soja em campo natural dessecado (SDD). Utilizando um simulador de chuvas de braços rotativos, foram aplicados três testes de chuva, com intensidade constante de 64 mm h-1 e com durações suficientes para a enxurrada atingir taxa constante, sobre um Nitossolo Háplico alumínico, com 0,18 m m-1 de declividade média. O 1º teste foi aplicado cinco dias após a semeadura da soja, e o 2º e 3º, 30 e 60 dias após o primeiro, respectivamente. A concentração e a perda total de nitrogênio, fósforo, potássio, cálcio e magnésio na água da erosão hídrica foram maiores no PCO do que nos demais sistemas de manejo do solo.Water erosion causes soil degradation, which is closely related to nutrient losses either in, the soluble form or adsorbed to soil particles, depending mainly on the adopted soil management system. This study was carried out in São José do Cerrito, SC, Brazil, between March 2000 and June 2001. The objective was to quantify available nitrogen, phosphorus, potassium, calcium and magnesium losses in water erosion obtained with simulated rainfall in the following soil management systems: conventional tillage with no-crop (bare soil) (BS), conventional tillage with soybean (CT), reduced tillage with soybean (RT), no tillage with soybean on a desiccated and burned natural pasture (DBNP), and no tillage with soybean on a desiccated natural pasture (DNP). A rotating boom rainfall simulator was used to perform three rainfall tests with constant intensity of 64 mm h-1 and sufficient duration to reach constant runoff rate, on a clayey-loam, well-structured Typic Hapludox, with an average slope of 0.18 m m-1. The first test was carried out five days before soybean emergence and the second and third at 30 and 60 days, respectively. The nutrient concentration in water and total losses of nitrogen, phosphorus, potassium, calcium and magnesium were higher under CT than in the other soil management systems

Preparo do solo, erosão hídrica, perdas de cálcio, magnésio e carbono orgânico

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 de cálcio e magnésio na água da enxurrada superficial foram observadas sob PC, enquanto nos sedimentos as maiores concentrações ocorreram sob PM. A concentração de carbono orgânico nos sedimentos não diferiu nos tratamentos de preparo do solo, contudo, as perdas totais foram maiores sob PC.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

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

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

Nutrient losses by water erosion Perdas de nutrientes na água da erosão hídrica

Water erosion causes soil degradation, which is closely related to nutrient losses either in, the soluble form or adsorbed to soil particles, depending mainly on the adopted soil management system. This study was carried out in São José do Cerrito, SC, Brazil, between March 2000 and June 2001. The objective was to quantify available nitrogen, phosphorus, potassium, calcium and magnesium losses in water erosion obtained with simulated rainfall in the following soil management systems: conventional tillage with no-crop (bare soil) (BS), conventional tillage with soybean (CT), reduced tillage with soybean (RT), no tillage with soybean on a desiccated and burned natural pasture (DBNP), and no tillage with soybean on a desiccated natural pasture (DNP). A rotating boom rainfall simulator was used to perform three rainfall tests with constant intensity of 64 mm h-1 and sufficient duration to reach constant runoff rate, on a clayey-loam, well-structured Typic Hapludox, with an average slope of 0.18 m m-1. The first test was carried out five days before soybean emergence and the second and third at 30 and 60 days, respectively. The nutrient concentration in water and total losses of nitrogen, phosphorus, potassium, calcium and magnesium were higher under CT than in the other soil management systems.<br>A erosão hídrica causa o empobrecimento dos solos, devido ao transporte de nutrientes, os quais são transportados tanto adsorvidos aos colóides do solo quanto solubilizados na água, podendo variar com o sistema de manejo solo. O trabalho foi conduzido em São José do Cerrito (SC), entre março de 2000 e junho de 2001, com o objetivo de quantificar as perdas de nitrogênio, fósforo, potássio, cálcio e magnésio na água da erosão hídrica sob chuva simulada, nos seguintes sistemas de manejo: aração+duas gradagens sem cultivo do solo (SSC), aração+duas gradagens com cultivo de soja (PCO), escarificação+uma gradagem com cultivo de soja (CMI), semeadura direta de soja em campo natural dessecado e queimado (SDDQ) e semeadura direta de soja em campo natural dessecado (SDD). Utilizando um simulador de chuvas de braços rotativos, foram aplicados três testes de chuva, com intensidade constante de 64 mm h-1 e com durações suficientes para a enxurrada atingir taxa constante, sobre um Nitossolo Háplico alumínico, com 0,18 m m-1 de declividade média. O 1º teste foi aplicado cinco dias após a semeadura da soja, e o 2º e 3º, 30 e 60 dias após o primeiro, respectivamente. A concentração e a perda total de nitrogênio, fósforo, potássio, cálcio e magnésio na água da erosão hídrica foram maiores no PCO do que nos demais sistemas de manejo do solo