my first real food plot, tips / helps with growing.

hi guys.. well its been a few months... food plot is working out "o-k" i only seemed to get about 10% germination rate on my corn.. and probably 60% on my beans.. biggest downfall is i didnt get enough of the hay killed. and the hay started growing in well before the corn, i had a feeling this might end up the case.. but given the tools i had im overall satisfied with my results.. that being said im already thinking about next year.. and now that i have my own disc, i should have no problem killing the hay. one of my buddies was telling me that come fall/winter i should put cardboard over all the hay i wanted to kill off for next spring, and then disc it into the ground next spring. has anyone ever tried this? it seems to make sense to me.