Veal calf liquid manure effects on Collembola populations.

The effects of enrichments with liquid manure from veal calf fed exclusively on a powdered milk diet on Collembola populations were investigated. The manure was sprayed in a single application in different seasons and amounts in two contiguous parts of a field. Enrichment performed in autumn with a dose containing N-NH4+/ha at the maximum threshold used for agronomic management resulted in a consistent numerical decrease of the Collembola as a whole two weeks after treatment, whereas in June following spraying with one half the dosage, the Collembola number did not change. The results obtained with the two treatments can be attributed to the different species composition of the Collembola population in the two seasons, in addition to the different sensitivity of individual species to the treatment dosage. Enrichment with even marked amounts of veal calf liquid manure in a single dosage did not seem to have persistent impact, since changes in the biocenosis generally recovered in a relatively short time.