The combined acreage of these crops any year will exceed 3 million acres. Nodulation is one of our better diagnostic tools for gauging relative crop conditions. Legumes in stress will have limited nodule numbers. Severe stress after nodulation can cause nodule sloughing.
Stress can be from several sources.
However, drought and nutritional deficiencies are most common. Wet saturated soils also can reduce or eliminate nodule formation. Legumes depend on nodule growth for their nitrogen supply. Hence, stress and reduced nodulation can mean a nitrogen shortage before the crop matures. This can be seen each year somewhere in North Dakota dry bean and soybean crops.