Lixiviação de potássio da palha de espécies de cobertura de solo de acordo com a quantidade de chuva aplicada
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Data
2003-04-01
Autores
Rosolem, Ciro Antonio [UNESP]
Calonego, Juliano Carlos [UNESP]
Foloni, J. S. S. [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Brasileira de Ciência do Solo
Resumo
Os restos vegetais deixados na superfície do solo em sistemas de semeadura direta, além de proteger o solo da erosão, constituem considerável reserva de nutrientes que podem ser disponibilizados para a cultura principal, subseqüente. Avaliou-se a lixiviação de K da palha de seis espécies vegetais com potencial de uso como plantas para cobertura do solo de acordo com a quantidade de chuva recebida após o manejo. Milheto (Pennisetum americanum, var. BN-2), sorgo de guiné (Sorghum vulgare), aveia preta (Avena strigosa), triticale (Triticum secale), crotalária juncea (Crotalaria juncea) e braquiária (Brachiaria decumbens) foram cultivados em vasos com terra, em casa de vegetação, em Botucatu (SP). Aos 45 dias da emergência, as plantas foram cortadas na altura do colo, secas em estufa e submetidas a chuvas simuladas de 4,4, 8,7, 17,4, 34,9 e 69,8 mm, considerando uma quantidade de palha equivalente a 8,0 t ha-1. A máxima retenção de água pela palha corresponde a uma lâmina de até 3,0 mm, independentemente da espécie, praticamente não ocorrendo lixiviação do potássio com chuvas da ordem de 5 mm. A máxima liberação de K por unidade de chuva ocorre com lâminas de até 20 mm, decrescendo a partir deste ponto. A quantidade de K liberado da palha logo após o manejo depende da espécie vegetal, não ultrapassando, no entanto, 24 kg ha-1 com chuvas da ordem de 70 mm, apresentando correlação positiva com a concentração do nutriente no tecido vegetal. O triticale e a aveia são mais eficientes na ciclagem do potássio.
Besides protecting soil from erosion, plant residues left on the soil surface by green cover crops in no-till cropping systems represent a considerable nutrient source of nutrients that can be made available for the following crop. Potassium leaching from the straw of six cover crop species was evaluated, in relation to the amount of rain on the residues. Pearl millet (Pennisetum americanum), guinea sorghum (Sorghum vulgare), black oat (Avena strigosa), triticale (Triticum secale), Indian hemp (Crotalaria juncea) and brachiaria (Brachiaria decumbens) were grown under greenhouse conditions in pots with soil, in Botucatu, State of São Paulo, Brazil. Forty-five days after emergence, the plants were cut, dried and placed in PVC rings, simulating an amount of 8 t ha-1 of straw. Rainfalls of 4.4, 8.7, 17.4, 34.9, and 69.8 mm were applied. The straws retained up to 3.0 mm of water, irrespective of the plant species, and rains of 5 mm did not cause K leaching. Maximum K leaching per rain unit was observed for rainfalls around 20 mm, and decreased under heavier rainfalls. The amount of K released from the straw right after preparation is species-dependent, but is always below 24.0 kg ha-1 under rains up to 70 mm, and positively related with tissue nutrient contents. Triticale and black oats are more efficient at recycling K.
Besides protecting soil from erosion, plant residues left on the soil surface by green cover crops in no-till cropping systems represent a considerable nutrient source of nutrients that can be made available for the following crop. Potassium leaching from the straw of six cover crop species was evaluated, in relation to the amount of rain on the residues. Pearl millet (Pennisetum americanum), guinea sorghum (Sorghum vulgare), black oat (Avena strigosa), triticale (Triticum secale), Indian hemp (Crotalaria juncea) and brachiaria (Brachiaria decumbens) were grown under greenhouse conditions in pots with soil, in Botucatu, State of São Paulo, Brazil. Forty-five days after emergence, the plants were cut, dried and placed in PVC rings, simulating an amount of 8 t ha-1 of straw. Rainfalls of 4.4, 8.7, 17.4, 34.9, and 69.8 mm were applied. The straws retained up to 3.0 mm of water, irrespective of the plant species, and rains of 5 mm did not cause K leaching. Maximum K leaching per rain unit was observed for rainfalls around 20 mm, and decreased under heavier rainfalls. The amount of K released from the straw right after preparation is species-dependent, but is always below 24.0 kg ha-1 under rains up to 70 mm, and positively related with tissue nutrient contents. Triticale and black oats are more efficient at recycling K.
Descrição
Palavras-chave
ciclagem de nutrientes, cobertura morta, precipitação, semeadura direta, cover crops, no-till, nutrient cycling, rains
Como citar
Revista Brasileira de Ciência do Solo. Sociedade Brasileira de Ciência do Solo, v. 27, n. 2, p. 355-362, 2003.