If you do this it’s very interesting but you can’t do anything can you? Pyrethroid contact only on the adults? Mine are being hammered but haven’t sprayed.Weevil are still chewing at mine. I did put manganese in with the pyrethroid.
I've got 3 fields of beans that had sewage cake last autumn. Not in a NVZ thankfully - the heap had to be spread. I'll report back when they are a bit further ahead. The seedbed was wobbly and they are still emerging, so no comparison yet.
Dig some up, wash the soil off the roots carefully in a bucket and see if there are many larvae feeding on the root nodules.
The odds of making much of a difference to the weevil levels are not good and I have left most of them untreated to see whether I’m just wasting time and beneficials.If you do this it’s very interesting but you can’t do anything can you? Pyrethroid contact only on the adults? Mine are being hammered but haven’t sprayed.
I chucked some beans in an oat crop just to see what happens. Gave it 50kgN of liquid and this is the result. At least I won’t need to spray them out!!!
If there is excess nitrogen in the soil legumes don't tend to nodulate. In my eyes you would be spending money on Nitrogen that nature will be providing for free.