Question:

We have a grower who has probably 90+% inoculation failure (on new and old peanut ground).  He has hit it with nitrogen, but we are still trying to get to the bottom of it. Plant dates range 5/3-5/20 with slightly less than optimal moisture, but not dry by any means. In-furrow applications included inoculant, generic imidacloprid, and a commercial product at 10 GPA. 60-70% emergence across the board (noticed the seed quality was not great across varieties, plant dates, and soil types, and a lot of plants germinated then rotted under relatively ideal conditions). We first noticed the inoculant failure 40 DAP and by 60-70 it was widespread. It does not appear to follow any rotation pattern strictly speaking, although fields that have had fumigant recently appear to be in a little bit rougher shape (but there are exceptions even then).

There were issues with Molybednum (Mo) in samples. Could the lack of tissue Mo cause the lack of nodulation?  Also, is it possible that the in-furrow mix could have altered the solution (pH or other factors) in a relatively quick period of time to kill the inoculant?

Jordan:

Almost anything outside of inoculant, insecticide and perhaps fungicide concerns me when it comes to in-furrow treatments. Inoculant and insecticide contribute to peanut yield. Other items in the tank are either neutral and in some cases negative. I do not know anything about the product in question, but anything that drives down pH to low levels could negatively affect bacteria in formulated inoculant. We know inoculant performs poorly if at all under low soil pH and that this is, at least in part, due to an acidic environment that can be lethal. I suspect the same thing can happen in the spray tank if something added creates a low pH environment. I do not know how quickly the bacteria would die, but if pH is very low, it might happen quickly as described.

Fumigation could have killed any native bacteria but should not affect the applied product in peanuts. Native bacteria might help alleviate issues with applied inoculant that does not work, so more issues after fumigation might show up.

Molybdenum is an important component of the nodule complex for BNF. If it is low, BNF will suffer.

Going forward, in new ground fiends I recommend the in-furrow inoculant but also for insurance, the pest-based products in the hopper with seed. If something happens with the liquid spray, the peat material will allow for some BNF (although erratic and not always uniform, it can be acceptable compared with applied N for correction).

Question:

The only thing I think that is left is in regard to the Molybdenum. Is the low Mo a response to a lack of initial nodulation?  Or do I have that thinking backward?

Jordan:

I think it is the opposite. Low Mo results in less nodulation and/or nodulation activity.