Humus and Amino Acid Contents in Top Soil S21
Scheller, E.1 ; Bachinger, H.2 & Raupp, J.3
1) Kwalis GmbH, Fuldaer Str. 21, D-36160 Dipperz. 2) ZALF, D-15374 Müncheberg. 3) Institute for Biodynammic Research, Brandschneise 5, D-64295 Darmstadt
|One of the basic ideas behind organic farming is
the use of organic manure produced by the animals on the farm itself to fertilize the
soil, while at the same time the use of mineral nitrogen fertilizers is forbidden. A large
number of experiments have been carried out, providing evidence that cattle manure in
particular increases the humus content and soil fertility. In cattle manure, up to 60-70 %
of the nitrogen present are protein-bound amino acids. The following questions arise as a
result of the different fertilizing practices employed in conventional and organic
- What effect do mineral fertilizers have on the amino acid content of the soil, in relation to cattle manure?
- How important are the amino acids in the soil for the build-up of humus and the fertility of soils?
It has been proposed by Mr. Mayer, a farmer, that amino acid contents of soils should be analyzed, as he suspects that there may be a connection between these and the build-up of humic substances. Analysis on sandy soils indicate that approx. 40-50% of the total nitrogen content of the top soil is present in the form of amino acids. The composition of amino acids in sandy soils from various regions was almost identical. In soil samples from the fertilizer trial carried out over a period of 15 years by the Institute of Biodynamic Research in Darmstadt (mineral - organic - biodynamic), the effect of mineral fertilizers, composted cattle manure and biodynamic preparations on the amino acid content of the top soil was examined. The trial was established with three levels of fertilization for each type of fertilizer, and each variant was repeated four times. After just a few years, it could be seen that the mineral-fertilizer treated plots had the lowest, and the biodynamic treated plots the highest humus content. The amounts of the different amino acids in the organic and biodynamic plots increased with increasing amounts of farmyard manure. On the mineral fertilized plots an increase of Asp, Glu, Ser, Gly and Val was noted in the highest level of fertilization, the other amino acids either remained unaffected, or showed a tendency to decrease. At the same level of fertilization (2 and 3), the amino acid contents increased significantly from mineral to organic to biodynamic.
The amino acid composition (amino acids/g N) is almost identical in all the variants. It may therefore be assumed that the protein structure in humus of arable sandy soils of a larger region is the same, even if various types of fertilizer are used. Humus synthesis might only be possible if all the necessary amino acids are available or added, and in the correct proportions to one another. The supply or synthesis of essential amino acids could be a limiting factor for the synthesis of humic substances.