EFFECTS OF COMPETITION AND WATER DEFICIT ON SUNFLOWER AND WEED GROWTH

Abstract

In the agricultural environment it is common the occurrence of biotic and abiotic stress, such as weed interference and soil water deficit. The understanding of this interaction may contribute to the development of efficient weed management strategies. In this way, the objective of this work was to evaluate the effects of competition and water deficit on the growth of sunflower and weeds. The experiment was carried out in a randomized block design, with four replications. The treatments were arranged in factorial 5x2, with the first factor corresponding to the competition arrangements between the species (sunflower + W. indica; sunflower + A. spinosus; sunflower, W. indica and A. spinosus in monoculture), and the second of water regimes (irrigated and water deficit). The water deficit was established when the sunflower plants had six expanded leaves - V6 stage and maintained until the rate of CO₂ assimilation of the plants reached values close to zero (6 days), when irrigation was resumed. Competition between plants reduced the growth of sunflower, W. indica and A. spinosus. The species W. indica and A. spinosus aggravated the negative effects of water deficit on sunflower growth. The water deficit did not affect the growth of the specie W. indica. A. spinosus was more competitive with sunflower than W. indica.