European Code of Conduct document … some very nice terminology definitions included
Book Recommendation - Growing a Revolution, Bringing Our Soil Back to Life by David R. Montgomery. The book is about using no till methods to improve the soil and reduce costly inputs. He describes various methods used in the US and around the world. He concluded that farmers can do less work, reduce their costs and produce higher yields by improving their soil and sequestering carbon as a bonus.
Not open source, but I thought someone might be interested is this food technology event.