The K-trial. A 33-years study of the connections between manuring, soils and crops

Summary

In 1958 started a comparative fertilization trial, called the K-trial, within the frames of Scandinavian Research Circle for Biodynamic Agriculture. The trial ended in 1990. This report accounts for the results that have been collected over this 33-year long trial-period.
The ambition with the trial was to develop methods of analyses that could indicate foodstuff quality. The long-term trial-period also brought along, a possibility to study the correlation of fertilization, soil and crop.
The difference between a cultivation that uses organic fertilizer compared to one that uses mineral fertilizer and where both achieves comparable yield-levels can according to the results from the K-trial be summarized as:
Soil
- higher enzyme-activity, soil respiration and occurrence of earthworms
- more deep going soil processes
- considerably higher nitrogen-mineralising capability
- better soil-fertility
Crop
- better storage efficiency and resistance against decomposition
- higher grade of maturity
- higher amount of leguminous plants in the clover/grass ley
The results from the K-trial in this report, has been compared to the results from two ”daughter-trials”. In these trials two different systems was compared, biodynamic agriculture and conventional agriculture. The effects of these different fertilizing-systems on the quality in products in the K-trial corresponded with the results from the daughter-trials. In comparison with the conventional methods, the crude protein content was lower in the organic variants, but the quality in the protein was higher in potatoes and wheat. Resistance against decomposition and storage-quality for potatoes, was higher in the organic variants and the same applied to the starch-quality in wheat. The organic fertilisation resulted in a higher fertility in soil and crops, with higher quality in protein and starch.
The differences were more difficult to determine between de variant that was fertilized with compost and the ones that received raw farmyard manure, partly because the compost was also treated with the biodynamic compost-preparations. Somewhat simplified, the differences consisted in the fresh farm-yard manure more strongly did stimulate the vegetative processes and the metabolism in soil and crop, while the compost more strongly contributed to building up the soil structure and the form of the crop.
The biodynamic field-preparations effects could be determined as a positive effect on the yield in all crops, except the first harvest of clover/grass ley. The effect of the preparations on yield was largest during the years when yield-level was low. Field-preparation effects were also apparent in the more deep-going soil processes, and in higher amount-amount in the clover/grass ley. This calculated supply of nitrogen by this higher amount of amount plants amounted to approx. 16 kg N per hectare and year.
The results from the K-trial indicate the demand of a discussion on issues concerning food-stuff-quality. In this report a few aspects on the concept of quality has been treated.
Furthermore, formulated is also a frame of a few possible future research-fields connected to the issue of quality.