Weeds pose significant challenges limiting productivity and profitability in agricultural production systems. Properly managing these plants is fundamental in developing Conservation Agriculture systems, and incorporating ecological concepts must base a weed management program. Cultural practices that allow more space occupation by cultivated plants and limit the development of weeds are discussed. Crop rotation, cover crops, and permanent soil cover are essential practices in Conservation Agriculture systems. The effect of these practices on weed seed bank, space occupation, competition for resources, and weed population density are also discussed. Case studies exemplify the theoretical concepts.