Decreasing methane emission of rice by better crop management

A field experiment was conducted to determine the effect of water management techniques for maintaining rice production and reducing methane emission in a Crowley silt loam paddy soil receiving high rice straw additions. A 2 × 5 factorial experiment was arranged in a split-plot design with two water management practices; alternately flooded and drained and continuously flooded, and five rates of rice straw incorporation as subplot treatments (0, 3, 6, 12 and 24 t ha–1), with four replications. Rice yield was significantly greater in the alternately flooded and drained treatment as compared with the continuously flooded treatment. High rice straw application (12 and 24 t ha–1) reduced rice yield in both water management treatments. Methane emission increased with increase in the rice straw application rate. However, emissions were lower in the alternately flooded and drained treatment plots. The results demonstrate that draining a field for a short period of time during the growing season can enhance rice growth and rice yield while reducing methane emission

Efeito de diferentes herbicidas na nodulação e na atividade da nitrogenase no amendoim Effect of herbicides on nodulation and nitrogenase activity in peanuts

Em ensaio de herbicidas na cultura do amendoim (Arachis hypogaea L.), realizado em Ribeirão Preto, SP, em 1984/85, sem o uso de inoculante, não foram encontrados nódulos nos diferentes tratamentos. Como é comum sua presença em amendoim nessa região, suspeitou-se que os herbicidas utilizados pudessem ter efeito inibitório na nodulação. Avaliou-se, então, o efeito de alachlor, linuron, oxadiazon, pendimetalin e trifluralin aplicados na dose recomendada, na nodulação e na atividade da nitrogenase, durante dois anos consecutivos, usando-se sementes inoculadas e não inoculadas. Foram feitas amostragens aos 28, 42, 63, 84 e 105 dias após a semeadura, observando-se nodulação abundante, em todos os tratamentos, e reduções ocasionais na nodulação e na fixação do nitrogênio, porém não consistentes nas diversas amostragens. A atividade da população nativa de Rhizobium em geral permaneceu num nível maior do que nos tratamentos com inoculação. Embora alguns herbicidas tenham afetado a nodulação e a fixação do nitrogênio, não houve influência na produção de grãos.<br>No nodules were found in a peanut herbicide trial held at Ribeirão Preto, State of São Paulo, Brazil, during the growing season 1984/85. Since spontaneous nodulation is commom in this region, a hypotheses was raised that herbicides could have an inhibitory effect on nodulation. To test the effect of herbicides on nodulation and nitrogenase activity an experiment was carried out on two consecutive years, using a factorial design with two factors: a) five herbicides (alachior, linuron, oxadiazon, pendimethalin and trifluralin) applied in usual dosages and a control without herbicide and b) with and without Bradyrhizobium inoculation. Samples were collected at 28, 42, 63, 84 and 105 days after planting. The results showed that nodulation was abundant in all treatments. Nitrogenase activity in the non inoculated treatments persisted for a longer period than in the inoculated ones. Although some herbicides reduced nodulation and nitrogen fixation, peanut grain production was not affected