Long-Term Field Experiment in Sweden: Effects of Organic and Inorganic Fertilizers on Soil Fertility and Crop Quality
Artur Granstedt & Lars Kjellenberg
Summary
In 1958, Bo D. Pettersson in the Nordic Research Circle for Biodynamic Farming in
Järna, Sweden, began an agricultural field experiment that lasted until 1990, i.e. 32
years. The field experiment included eight different fertilizer treatments, each with a
four-year crop rotation without repetitions: summer wheat, clover/grass mix,
potatoes, beets. The focus was primarily on aspects of crop quality, and the fertilizer
application rates for the various treatments were adjusted to bring about comparable
yields. Two "daughter experiments" emerged from the K-experiment and were run
in parallel with the mother project during 1971-1976 in Uppsala and 1971-1979 in
Järna.
In these experiments a comparison was made between two systems, biodynamic
farming and conventional farming, in which both fertilizer regimes and crop
rotations were studied. One of the main objectives in the K-experiment, i.e. to
obtain nearly the same yield over the experimental period in the organic-treatment
variants and in the inorganic treatments has largely been achieved, but there were
differences between crops.
During the time between 1958 and 1990 the yield increased in all treatments in
accordance with the overall trend in the Swedish agriculture, but the increase was
highest in the organic treatments (65 % in the biodynamic in comparison with 50 %
in the conventional). The effects of the different fertilizer treatments on product
quality are in accordance with findings in the two "daughter experiments" which
were based on the original K-experiment.
Compared with the conventional treatments, the crude protein content of potatoes
and wheat was lower in the organic treatments, but protein quality was higher (i.e.
relatively pure protein and essential amino acids, lower amount of free amino
acids). Resistance to decomposition and store quality for potatoes were higher in the
organic treatments, and in wheat starch quality seemed to be higher.
The organic treatments resulted in a higher soil fertility capacity and in crops with higher quality protein, a higher starch content, and a greater ability to tolerate
stressful conditions and long-term storage in comparison with the inorganic
treatments. Furthermore, the crops produced in the organic treatments developed a
structure that can be studied through a picture formation method (Crystallization
with CuCl2). This has also been described as a higher organizational level which is
evident in terms of both soil and crop formation as a result of the long-term effects
of organic manure compared with conventional NPK-fertilizer.
New experiments in Sweden and Finland have been started to study the effects of
different organic treatments on farms. Preliminary results of these experiments
confirm the described differences between organic and inorganic treatments, but
indicate also that the effects of liquid organic manure on quality parameters are
more similar to those of inorganic fertilizer.