Successful nodulation in peanuts is expected, but is not guaranteed.
Early season scouting of nodulation is advised for two reasons:
1. Assess early nodulation in advance of decisions about whether to apply mid-season nitrogen, and if so, how much.
2. Early identification of any field that might not have nodulated adequately so that supplemental nitrogen may be applied to help achieve yield potential.
Five to six weeks after planting, use a shovel to dig (don’t pull) plants to evaluate nodulation. If nodulation is judged poor, little can be done to increase nodulation. Ask why nodulation may be poor (see the above mistakes).
Minimal or nonexistent Rhizobium nodulation points toward the need for supplemental nitrogen to achieve desired yields so fertilizer nitrogen should be considered. Annually as many as 25 percent of fields in West Texas are under-nodulated, or worse, may have only a few nodules per plant. Poorer nodulation appeared to be somewhat correlated with caliche soils, where pH is greater than 8.0 may curtail Rhizobium effectiveness.
Nodule mass later in the season may be more important than number of nodules. Active nodules are pink to dark red inside. If nodules are white inside they are not yet active so check again in another week for reddish color. Older, inactive nodules are black, gray, or greenish inside.
Because of the importance of good Rhizobium nodulation on peanut production we suggest that early-season scouting of nodulation should be part of a comprehensive crop scouting program for peanut. If adequate nodulation is not achieved a response is needed to avert possible economic losses.
If early nodulation is good, you can expect it to continue to increase toward peak nodulation (usually August), but if early nodulation is poor it probably isn’t going to improve.