Crop diversification for weed management - Ecological Management of Agricultural Weeds - page 328

Figure 7.1 Stress and mortality factors affecting weeds in a simple two-year rotation and in a more diverse
four-year rotation.Both rotations are suitable for the midwestern USA.The two-year rotation uses
conventional weed management practices,whereas the four-year rotation uses practices commonly found on
low-external-input farms.The forage legume (e.g.,alfalfa or red clover) used in the four-year rotation is
planted with oat,which is harvested for grain in July.As indicated by symbols shown on lines labeled
“cumulative impact,”the timing ofstress and mortality factors is more varied and the duration ofcanopy
cover is greater in the more diverse rotation.(Adapted from Kelner,Juras & Derksen,1996,and Derksen,
1997.)