Crop Residues: Agriculture's Largest Harvest

Plant parts used for food and fiber, and crops grown for animal feed, do not produce most of the phytomass harvested annually by the world's agriculture-crop residues do.More than half of all absolutely dry matter in the global harvest is in cereal and legume straws; in tops, stalks, leaves, and shoots of tuber, oil, sugar, and vegetable crops; and in prunings and litter of fruit and nut trees.Consequently, it would not be inappropriate to define agriculture as an endeavor producing mostly inedible phytomass.Unfortunately, we cannot either accurately quantify this enormous harvest or satisfactorily account for its fate, which may help to explain why so little attention has been paid to crop residues: The latest US agricultural encyclopedia has no entry for either crop residues or straw (Arntzen 1994), and the only comprehensive interdisciplinary overview of cereal straw was published nearly a generation ago (Staniforth 1979).Nevertheless, there is no doubt that a large part of the residual harvest is handled inappropriately, weakening the world's food-production capacity and contributing to undesirable biospheric change.Such malpractice is particularly common in low-income countries, where inadequate amounts of residues are recycled Vaclav Smil (e-mail: