There were a lot of lambs quarters, a few pigweed, and an occasional giant ragweed. The idea is to cut off the seed head before those seeds are viable. This reduces the number of seeds in the fields "seed bank", making future cash crops easier to cultivate.
These fields, approximately, 90 acres, are in the first of two years of transition to USDA Certified Organic. The clover is thick and well established. It should overwinter and return stronger next spring, fixing nitrogen throughout the summer. In late summer (of 2020), I'll probably disc harrow the dying clover into the soil and plant a "tillage radish", which itself will winterkill. The following spring (2021) these fields will be planted to organic corn.