Tree Crops: A Permanent AgricultureTree Crops: A Permanent Agriculture, first published in 1929 and last updated in 1953 (and the edition reprinted here) is a classic, pioneering look at the use of trees for food, soil conservation, and sustainable agriculture. Author J. Russell Smith (1874 1966) travelled widely and shares his insights and research into agro forestry, describing how trees such as carob, honey locust, persimmon, mulberry, oaks and pecans can be used to enrich the land