If one week or more passes between bed preparation and planting, aggressive weed seedlings may begin to emerge. During planting, run a blade 1 to 1.5 inches below the soil surface to cut such seedlings, giving the beans a head start on emerging weeds. This practice conserves more soil moisture than other cultural methods. Irrigating beans up, instead of planting into moisture, can cause soil crusting and lead to seed rot. It can also cause weeds to germinate simultaneously with the beans.
Furrow irrigating up is especially risky on heavy clay soils.
After bean plants are established, cultivation with sweeps, knives, or rolling cultivators can significantly limit the growth of weeds that may have survived earlier cultural or chemical control methods. Late season weed infestations may not seriously affect bean yields. However, such weeds often hinder harvest operations and increase harvesting and cleaning costs. In addition, weeds produce a lot of seed that remains in the soil and can infest succeeding crops. During threshing, berry juices stain the beans, and sticky seeds may slow down or clog the thresher.