Digging in green manure

Due to the dry early spring, I've had very disappointing results with my spring green manure this year. It grew leggy and when the rain finally came it was a bit too late for it to bulk up much. 

But I still need to prepare my brassica bed soon so this mustard/phacelia/rye grass mix is going in. I was not happy with the number of red ants/ant eggs I saw when I dug the chopped foliage in. The allotment is very bad for red ants and I'm finding more and more each year - doubtless because of the long dry spells we get.