Efeito da adição de BHC no solo, sôbre o desenvolvimento do milho Effect of BHC in the soil on growth of the corn plant

• Main Authors: Coaracy M. Franco, Constantino G. Fraga Jr.
• Format: Article
• Language: English
• Published: Instituto Agronômico de Campinas 1960-01-01
• Series: Bragantia
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87051960000100003

Como o milho é freqüentemente cultivado em solo anteriormente ocupado pela cultura algodoeira, achou-se conveniente verificar se o BHC empregado nesta última cultura poderia permanecer no solo e prejudicar aquela planta. Com êste objetivo fêz-se um ensaio em vasos de Mitscherlich, no qual diferentes doses de BHC foram incorporadas à terra. As doses de BHC empregadas foram correspondentes àquelas recebidas pelo solo no fim de 1, 2, 3, 4 e 5 anos de cultura algodoeira, tratada com a quantidade oficialmente recomendada daquele inseticida (108,5 kg/ha/ano, de BHC contendo 2% de isômero-gama). Nos vasos, onde as condições eram as mais favoráveis para o manifestação dos efeitos tóxicas do BHC, a decomposição dêste inseticida na terra foi suficientemente rápida para que os efeitos tóxicos de uma dose três vezes mais forte do que a oficialmente recomendada desaparecessem completamente no fim de dois anos. Nas condições de cultura os efeitos tóxicos do inseticida devem ser ainda bem menos intensos. Não são de se esperar, pois, prejuízos à cultura do milho, causados pelo acúmulo de BHC no solo, quando aquela fôr feita em terreno anteriormente ocupado pela cultura algodoeira, desde que nesta a quantidade empregada do inseticida, não tenho sido muito diferente daquela oficialmente recomendada.<br>Corn is frequently cultivated on soil previously used for cotton. Cotton plantings usually receive heavy applications of BHC for insect control, what might lead to an accumulation of the insecticide in the soil. An attempt was made to verify whether varying amounts of BHC added to a sandy soil in Mitscherlich pots would injury corn plants. The amounts added were calculated on an area basis to correspond to those received by the land at the end of 1, 2, 3, 4 and 5 years of cotton cultivation when BHC is applied at the yearly rate of 108 kg per hectare. Other types of soil were not used in this experiment because the toxic effects of this insecticide seem to be more serious on sandy soils. Other techniques employed in this work were exactly the same described in a previous paper (1). The experiment was terminated one month after sowing and the weights of the plant tops and roots were determined. The soil from the pots was passed through a sieve after harvesting, returned to the pots and left undisturbed for one year. Corn was then planted a second time on the same soil. In the first planting, dose 1 had no injurious effect on plant growth, but the heavier doses depressed it severely. In the second planting only doses 4 and 5 showed injurious effects, but injury was less severe than that in the first planting. The results seem to indicate that there is practically no risk that residual BHC in the soil from a previous cotton planting that received standard applications of the insecticide will injury corn plants raised on the same land the following year.