Weeds are any plants that grow where they are not wanted. They compete with the cultivated crops for nutrients, moisture, sunlight, and space. They shelter pests and diseases that attack the crop. They reduce crop yields and farmers’ incomes. Controlling weeds can be a lot of work.
In conventional farming, tillage is a major way to control weeds. Farmers plough repeatedly in order to suppress weeds and have a clean field when they plan their crop. Ploughing buries many weed seeds, but it also brings other seeds back to the surface, where they can germinate. Burning crop residues may also stimulate the growth of some types of weeds.