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.

Inhalt

1. Organic residues in modern agriculture.- Section 1: Nitrogen and phosphorus supply to plants by organic matter and their transformations.- 2. Effects of organic matter on nitrogen and phosphorus supply to plants.- 3. The role of organic matter and ammonium in producing high corn yields.- 4. Nitrogen transformations in Histosols.- Section II: Effects of soil organic matter and redox on micronutrients availability to plants.- 5. Soil organic matter interactions with trace elements.- 6. Effect of soil redox conditions on microbial oxidation of organic matter.- Section III: Soil microorganisms, biofertilizers and biocontrol agents: their interactions with soil organic matter and effects on soil fertility.- 7. Soil microorganisms, soil organic matter and soil fertility.- 8. The role of organic matter in the introduction of biofertilizers and biocontrol agents to soils.- Section IV: Effects of soil organic matter and applied sewage sludge on soil structure and fertility.- 9. Soil organic matter extraction, fractionation, structure and effects on soil structure.- 10. Sewage sludge organic matter and soil properties.- Section V: The use of peat and composts as container media.- 11. Peat and peat subsitutes as growth media for container-grown plants.- 12. Effects of composts in growth media on soilborne pathogens.