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Burlington, IA | White on the interior indicates colonization by rhizobia, but are not yet mature or actively fixing N. Check them again in a few weeks. The window for evaluating nodulation starts at 40 days following emergence, and runs until pods start to fill. Digging and washing is the preferred method. Pulling plants can cause nodules to be separated from the roots, so you may have missed some. Don't know your planting date, but if you're barely 40 days after emergence, you might want give it a little time. Pink to bright red indicates actively fixing N. Green, tan, brown, black, or mushy, indicates not active, ineffective, or parasitic. There should be at least 8 to 20 big healthy nodules per plant. But look at the overall mass of nodules, not just the quantity of nodules.
Hth,
JDH
Edited by JDH SE IA 7/20/2010 19:35
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Soybean nodule color ?
