The use of organic residues as a means of maintaining and increasing
soil fertility is of long-standing. This tradition has been somewhat
neglected since the introduc- tion of mineral fertilizers at low cost.
More and more farmers and scientists are now showing renewed interest in
the proper and effective use of org tnic residues, composts and other
recycled organic additives. The role and function of organic amendments
in modern agricultural systems have become topics of major interest in
the scientific and agricultural communities. Research work on residue
disposal has provided new concepts on the interaction between organic
components and soils as well as new handling technologies (e. g.
pelletizing of organic residues). The trend to conserve energy has led
scientists to study the minimal tillage system, to find ways of
replacing conventional inorganic fertilizers with natural organic prod-
ucts or microbial preparations, and to develop new composting methods.
The drive to achieve higher yields in commercial greenhouse farming has
led to a search for optimum substrates as growth media and for improved
management techniques. This has led to the introduction of organic
substitutes for peat, nota- bly those originating from agricultural
wastes. Another important aspect is the current interest in organic
farming, where use of synthetic chemicals is avoided or prohibited. An
increasing percentage of the population in highly developed countries is
willing to pay premium prices for food produced on soils where inorganic
fertilizers and other agricultural chemicals have not been used.