Soybean response to potential alleopathic activity of sugar cane

Abstract

Crop rotation is performed to give the land a rest period and eliminate or reduce the incidence of weeds and pests. However, each plant species excretes chemical compounds that may affect other plants (allelopathy), conditioning rotation schemes. In sugarcane, rotation is mainly done with soybean. This study evaluated the existence of allelopathic effects of sugar cane on soybean. Two trials using sugar cane leaves and stumps were performed. In the first, soybean was sown in pots with various concentrations of either leaves or stumps in the soil. Germination percentage, plant height, root length, fresh weight and dry weight were determined. Towards the end of the crop cycle, the plants were harvested and grain number, grain number per pod and grain weight was determined. In the second trial, soybeans seeds were irrigated with different concentrations of extracts of either leaves or stumps. The number of germinated seeds was determined. Subsequently radicle and hypocotyl length was determined. The results show that there are allelopathic effects. These effects were not equally expressed in the different plant parts evaluated. For sugar cane leaves, the most affected parameters were number of grains, number of pods and crop yield; whereas for the stumps, values were equal or even higher than the control. These results have implications for the planning of rotation schemes so larger scale evaluations are recommended.