Amino acid and soil organic matter content of topsoil in a long term trial with farmyard manure and mineral fertilizers

Summary

Commencing in 1980, a long-term experiment is carried out to compare mineral fertilizers (MIN), composted manure (CM) and composted manure with application of biodynamic preparations (CMBD) at three different fertilizer application rates. With mineral fertilizer the lowest contents of 0.80% C and 0.069% N, with manure 0.90% C and 0.080% N, and with manure and biodynamic preparations 1.08% C and 0.094% N were achieved in the topsoil. 42.9 to 53.7% of Nt was bound in 18 protein amino acids including asparagine and glutamine. Amino acid contents in the hydrolysates of the topsoil were significantly different according to fertilizer type: MIN < CM < CMBD. The higher contents in manure fertilized plots were observed even at the lowest rate of fertilizer application. This indicates that differences between the treatments do not depend only on the amino acid supply from manure, but are also influenced by a changed amino acid metabolism in the soil.