SOIL FERTILITY IMPROVEMENT AND POLLUTION RISKS FROM THE USE OF COMPOSTS REFERRED TO N, P, K AND C BALANCE.

Experimental results from a fertilization trial are presented in which composts of different origin, at various rates of application, in comparison with mineral fertilizers and farmyard manure have been applied annually to a maize crop on the same site for five years.

The aims of this study were: the determination of soil fertility increased and the evaluation of potential pollution risks in relation to N, P, K and C balance.

The most important results were:

• N (total): organic manures application increase the N content of the soil; the increments, for the maximum rates of application, were about 45%. Treatments manured with municipal solid wastes plus sewage sludges (MSW+SS) compost gave severe losses in N, exceeding 50% of the applied rate.
  However, lower losses were observed in the plots manured with FYM or MSW compost.

• P: maximum soil total P increments were observed with FYM (+ 133%); particularly high was the increase (+ 69%) with the heavier MSW+SS compost dressing.
  Also available P content showed an average variation of about 100% for the MSW+SS compost, and even 900% in the case of FYM. Balance determination gave doubtful results.

• K: total K increments were not significant; therefore one can suppose that severe losses of applied K occurred.
  Available K content increased with both inorganic and organic fertilizers, with increments of about 80% in most of organic dressings.

• C (organic): the percentage of soil organic C significatively increased in the plots that received organic manures.

International Symposium on Compost Recycling of Wastes

B. Lionello, D. Francesco

https://doi.org/10.17660/ActaHortic.1992.302.5