I'd be inclined to chain harrow the field as soon as practical, to distribute the muck (or spread by hand), then see what emerges once the weather warms up. Southdown sheep were traditionally used to graze the hilltops of the Downs during the day and folded back on the flatter fields around the farmhouse at night, thus bringing the fertility of the short chalkland grasses back to the arable and haymaking fields. (They had shepherds with them all day, which is one of the reasons they're so docile.)