|Bioconversion of Organic Residues for Rural Communities (UNU, 1979)|
|Availability of organic residues as a rural resource|
At issue was the implication, drawn from the preceding papers, that it is less desirable to return agricultural residues to the soil than to process them for feed or other purposes. It was pointed out that ploughing back the residues helps to prevent erosion, thus conserving soil and water and maintaining the soil structure. An estimated 3,000 million tons of topsoil are said to be lost annually in the United States from the cultivation of corn, cotton, and other crops, in addition to the loss of 123 kg per hectare of nitrogen by the removal of residues.
Ploughing back residues significantly improved subsequent crop yields in the Guatemalan highlands where the soil had an initial humus content of less than one per cent.
While examples of the benefits of returning residues to the soil could be given in some instances, in other places there would be no such advantage. In these cases, the chemical treatment of straws before their use for feed could be a better method of residue management. It is simple, it has been demonstrated to be practical, and there is a demand for the feed, although the economics and magnitude of various methods of treatment in any particular set of circumstances remain to be determined.