NUTRIENT EXTRACTION OF WEEDS IN COMPETITI ON WITH THE CORN CROP (ZEA-MAYS L)

Two field trials were carried out to study the effects of different we ed control periods on the nutrient extration of weeds in the corn crop . The treatments were divided in two groups. In the first group the we eds grew together with the corn crop, since the sowing date until 00, 28, 42, 56, 70, 84 and 98 days after the crop emergence. In the second group, the crop was kept free since the crop emergence until 00, 14, 28, 42, 56, 70, 84 and 98 days of the corn cycle. In both essays, the predominat weeds were Indigofera hirsuta L. and Cenchrus echinatus L. The main conclusions were: I- In conditions of little weed interferenc e the nutrient extration for Indigofera hirsuta and Cenchrus echinatus were low and always were lower than the corn crop. 2- In conditions o f high weed interference the nutrient extration were higher than corn crop, mainly in calcium and potassium.