By September the Henry County fields have gone tall and tan, and a mowed yard stands out against them like a swept floor. Arthur’s Mowing and Firewood keeps yards and larger lots cut around Cambridge — mowing, trimming, edging, and the seasonal cleanups that follow the leaves down. Out toward Bishop Hill and Galva the properties get long, and a straight line held clean across an acre is worth stopping to look at. The last cuts of the year are the ones that decide how the spring begins. Cambridge and the towns that ring it.