Composition and Microbial Degradability in the Soil of Farmyard Manure from Ecologically-Managed Farms

ABSTRACT

Compared with usual reference values, liquid cattle manure from ecologically-managed farms (n = 13) had low average nutrient contents. In the case of solid manure obtained from cattle (n = 96) and from pigs (n = 18), the proportion of NH₄⁺ in the N_total (8.4% and 10.3% respectively), the CaO content (0.26% and 0.27% respectively) and, in the case of pig manure, the P₂O₅ content (0.57%), were all relatively low. On the other hand, the K₂O content of cattle manure (0.8%) was higher than that quoted in reference values. The manures from deep-litter stables had an above average content of K₂O (1.03%). The content of N_total decreased in the sequence deep litter stable > stanchion stable > sloping floor stable. The more frequently the manure heaps were relocated or rotated, and the older they became, the more the content of organic matter and in particular the percentage of K₂O in the mineral fraction declined.

The net mineralization of manure-C in the soil was between 6.9 and 53.1% after aerobic incubation for 10 weeks, and that of N between −5.4 and 19.5%. In the case of C, 75.2%, and in the case of N, 65.9% of the mineralization could be explained by the amounts of cellulose, hemicellulose, lignin, free amino acids, protein and heterocylic N compounds contained in the manures, as well as by their C:N ratio. The organic matter of manures from sloping floor stables was more readily and rapidly mineralized than the organic matter of manures from stanchion or deep-litter stables.