Insects controlled partially or entirely by rotation. Sugarbeet Weed control Rotations can be used to cause shifts in weed populations. Populations of certain weed species can be suppressed by competition from the crop raised or by the selective use of herbicides. Wild mustard populations can be reduced by selective treatment of small grain grown in rotation with row crops. Grass weed populations, often a problem in small grains, can be reduced by the use of the appropriate herbicide in the previous row crop.
Herbicides can have both beneficial and harmful residual effects on the next crop.
Therefore, planning the correct sequence of herbicide use together with crop selection has become a necessary part of rotation management. W-253, North Dakota Weed Control Guide, for specific herbicides and their potential for carryover injury on a subsequent crop. Soil nitrogen Legumes in the rotation can be used to increase the available soil nitrogen. Symbiotic nitrogen-fixing bacteria called rhizobia form nodules on the roots of legume plants and convert or fix atmospheric nitrogen to organic nitrogen. The amount of nitrogen fixed varies with species, available soil nitrogen, and many other factors.