Waste composts in organic crop rotation - risks and possibilities for the future

Summary

Organic agriculture aims at closed nutrient cycles, but currently the use of composts made of municipal waste is forbidden in Finnish organic production. The use of municipal waste composts in organic crop rotation and the risks connected with it in a long-term compost use will be studied.
The experimental plots received the previous compost applications in 2000 and the plots will be treated with the same types of waste compost in 2004 and 2005. The crop rotation from 2000 onwards is: cereal cover crop+clover-grass/clover-grass/clover-grass/cereal/potato/... and so on. Waste compost effects are compared to manure compost effects and control treatments with no fertilization applied. The waste composts are to be carefully selected with only the highest quality approved.
The indicator microbes of hygienity are determined from the composts applied on field experiment, and the viability of indicator microbes will be determined from soil samples two weeks after compost application. The nutrient and heavy metal content of composts will be analysed. Soil respiration, particulate organic matter and microbial C and N determinations will determine soil-improving effects. Nutrient cycling effects will be studied on nitrogen and phosphorus, with some enzyme activities, net N mineralization potential and soil nutrient contents determined. Plant yield and nutrient contents are also determined.