Why are my fields over-run with Black-Jacks?

We need to keep in mind that weeds are pioneer crops, whose main function is to help correct and restore soil to a higher ecological order, that is, to make soil more suitable for food producing crops. So, if one specific weed suddenly appears consistently, then one needs to realize something drastically has been changed in the make-up of the soil, either in the mineral availability, balance front or on the biological front. 

I believe the fact that when one has such a dramatic shift in weed spectrum it can be related to the effect of glyphosate on the soil. Black jacks are a classic symptom of extensive use of Glyphosate. The main effect of regular glyphosate use is the lock-up of Manganese (Mn), Zinc (Zn) and Boron (B). These pioneering weeds, then start popping up to help mobilize these locked up nutrients by producing root exudates which solubilize these tied-up nutrients. 

To avoid this invasion of black jacks occurring, you can chelate your glyphosate with fulvic acid, which reacts with the glyphosate and in so doing stops it from binding Mn, Zn and B. To try and turn back the wheel on fields that have this black jack problem, it is suggestible for you to use other non-round-up herbicides, like Simazine (if the crop is compatible). 

Alternatively, one could also use microbial products with humic acids in the growing crops. Microbials can change the environment around the roots from an oxidized environment (where nutrients like Mn and Zn are not plant available) to a reduced environment. This causes the tied-up nutrients to become plant available and takes away the reason for the blackjacks to thrive. Crop rotation is also very important and crops like oats, teff, alfalfa or soja beans are great in countering these situations where a pioneering crop/weed has taken over. 

Written by

Randolf Meyer