Long-Term Field Experiment in Sweden: Effects of Organic
and Inorganic Fertilizers on Soil Fertility and Crop Quality
(In Proceedings of an International Conference in Boston, Tufts University,
Agricultural Production and Nutrition, Massachusetts March 19-21, 1997.)
Artur Granstedt¹ & Lars Kjellenberg²
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
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
¹ Agricultural Research Centre of Finland, Partala Research Station
for Ecological Agriculture, FIN-51900 Juva, Finland.
²Biodynamic Research Institute, Skilleby, S-153 00 Järna, Sweden.
In 1958, Bo D Pettersson and the Scandinavian
Research Circle in Järna, Sweden, began an agricultural field experiment
to determine in what ways various types of fertilizers affect the soil
and final quality of grain and vegetable products. Various quality parameters
and quality-assessment methods were developed and tested during the experiment
period which spanned 32 years (up to 1990), and several reports have been
published (Pettersson, Reents & Wistinghausen, 1992).
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 (referred to as UJ-experiments in the following
text). 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 (Pettersson, 1982; Dlouhy, 1981). Before
that, the influence of these systems on quality parameters for potatoes
under different climatic and soil conditions also had been studied in different
parts of Scandinavia (Pettersson, 1970).
Description of the K-experiment
The K experiment was located at 59° North,
17° East at an elevation of 10 m above sea level. The mean yearly precipitation
was 550 mm, and the mean annual temperature was 6 degrees C, with 6-8 snow-free
months per year. The soil was a silty loam with an intermediate humus content.
Experimental Layout: To ensure that the field experiment could be used
for the plant quality assessments while providing the flexibility to support
other experiments that had yet to to designed, a very broad basis was adopted.
This scheme included eight different fertilizer treatments, each with a
4-fold crop rotation without repetitions. The size of each subplot was
36 m² gross, with a net harvestable area of 27 m².
The Crop Rotation: Within each fertilizer variant the following crops were
rotated without interruption so that in any given year all four would be
present: summer wheat (undersown with clover/grass), clover/grass mix,
potatoes and beets.
Fertilization Scheme: To facilitate focusing primarily on aspects of crop
quality, the fertilizer application rates for the various treatments were
adjusted to bring about comparable yields. This applies to the variants
1,2,3,4,7 and 8; variant 5 was not fertilized at all (Tables 1 and 2):
Table 1. The fertilization program (application rates of N- tot, P and
K in kg/ha/yr averaged for the years 1958-1990 in parentheses).
||Composted manure (82/38/76).: aged half a year with the addition of
biodynamic compost preparations 502-507 and biodynamic preparation sprays
500 and 501.
||Composted manure (82/38/76): same as in K1 with the exception that
treatments with biodynamic preparation sprays 500 and 501 were excluded.
||Raw manure (95/30/91): with horn and bone meal added to reach 1% contents.
||Raw manure + NPK (63/28/66): half the K3 manure rate; half the K6 NPK
||Inorganic NPK (19/19/41)
||Inorganic NPK(59/36/81): twice the rate applied in K6.
||Inorganic NPK(114/36/81): as in K6 but 4 times the N rate and twice
the P and K rates.
Table 2. Breakdown of the fertilization scheme within the rotation,
|K1, 2 & 3
|K6, 7 & 8
Description of the UJ-experiment
In the UJ experiment conventional (A) and biodynamic (B) treatments
were compared with each other in two crop rotations as described below
for the experiment in Järna (table 3): Crop rotation 1 represented
a rotation without animals, and crop rotation 2 represented a system with
animals related to an organic farming system which under Nordic conditions
is self-sufficient with fodder with 0.8 CU (cattle units)/ha (average 50
kg N/ha and year).
The field conditions were almost the same as those in the K-experiment.
A split-split-plot design was used with three replications. All crops were
grown each year. The soil was a silty loam well supplied with plant nutrients
but with a low humus content. The weather was drier than normal for the
region during the first years of the experiment period and had a strongly
negative effect on the yields of the grain and ley.
During 1971-1976 a parallel project was carried out in Uppsala (called
UJ-experiment Ultuna) with the same treatments as in Järna (for more
details see Dlouhy, 1981). The soil was an intermediate clay, well supplied
with plant nutrients and moderately rich in humus.
Table 3. Crop rotation and fertilization scheme in UJ Experiment in Järna
|ARTIFICIAL FERTILIZERS HERBICIDES
|Crop rotation A1
||Crop rotation B1
|Crop rotation A2
||Crop rotation B2
Yield and soil fertility
Yield in the K-experiment. The summer wheat and beet yields
were increased by fertilization, and a considerable difference was also
found between the K1 (compost + B-D sprays) and K2 (compost without sprays)
variants. Yields of clover/grass declined in response to fertilizer treatment
and were highest in the organic variants. A decrease in the yield of the
legume mix can be expected to result in a reduction in nitrogen fixation
(Table 4). In the K5 variant that did not receive any fertilizer for 30
years, the yield of ley was on the same level as that in the other treatments,
and also here, the yield tended to increase over the period, although the
increase was not as pronounced. Table 4. Average yields during 1958-1989
in dt/ha/yr for single crops
||(80 % moist.)
||(85 % moist)
In terms of their 32-year averages, the yields are all comparable with
the exception of the control variant (K5) and excluding data from the conversion
period for the organic treatments. All yields except for those of the unfertilized
variant (K5) increased with successive rotation periods (figure 1). The
figures indicate that there was a conversion period of about 8 years during
which the yield level was lower in the organic treatments.
Figure 1. K-experiment 1958-1989. Yield, MJ/ha
Development of soil fertility.
Data on soil physical properties, soil chemistry and soil biology were
collected after 19, 28 and 32 years in the K-experiment (Pettersson, Reents
and Wistinghausen, 1992). The analysis of soil data shows that nearly all
chemical (pH, P, K, Mg, C and N) (macronutrient availability was an exception)
and biological parameters (respiration, DHA, urease, earthworms) assessed
were improved by organic fertilization whereas no such improvements were
observed following the application of mineral fertilizer. Similar results
concerning soil parameters were obtained in the UJ-experiment (Pettersson,
1982). In the UJ-experiment at Järna, humus contents had increased
significantly after 9 years (by more than 10 percent) in B2 compared with
the recent value of 2.72 percent and the value of the conventional treatment
of 2.74 percent (A2B2 P<0.001).
The mineralization capacity of the soil was studied in summer wheat
after potatoes (the third year after ley) in the K-experiment. Net mineralization
in the soil was estimated by measuring the mineral nitrogen content of
soil samples taken in spring and at harvest and by determining the total
nitrogen uptake of the spring wheat crop (Granstedt, 1992). The mean mineralization
capacity during 1988-1990 was, on average, 95% higher (i.e. 106%, 146%
and 33% higher) in the organically farmed treatments as compared with the
treatments receiving commercial fertilizer. The higher mineralization capacity
compensated completely for the absence of applied mineral nitrogen in the
organically farmed treatment. In the organic manure system we built up
a more stable and higher mineralization capacity compared with the commercially
Quality of potatoes in the K-experiment (1958-1989) and
UJ-experiment (1971-1979) comparing biodynamic and conventional farming.
The main aims of the K-experiment were to study how product quality
is influenced by the fertilization system and to develop quality-assessment
methods. The K-experiment was designed with eight treatments and four crops
each year but without replications. Variation in mean values was generally
higher between years than between treatments, but the relation between
treatments for each individual year was mostly the same for most of the
response parameters. Still, it has been possible to compare the results
of biodynamic and conventional treatments in the K-experiment with those
from the above-described daughter projects. However, it should be kept
in mind that the K-experiment was limited to comparing fertilization regimes.
The UJ-experiments included a comparison between alternative and conventional
farming systems with respect to crop rotation and pesticide use (Dlouhy,1981
and Pettersson, 1982.)
The average tuber yield in the K-experiment was nearly the same in
the organic and conventional treatments, whereas the yield was significantly
lower in the unfertilized treatment (287 dt/ha). During years with higher
precipitation, when conditions were more conducive for the mineralization
of nitrogen in organic manure, organic treatments tended to outperform
the conventional ones. In both UJ experiments, with shorter experiment
periods, the yield was significantly lower (ca 20 percent) in the biodynamic
treatments, partly owing to the higher yield losses caused by Phytophtora
since pesticides were used in the conventionally fertilized treatments.
This difference was partly compensated for by a better storability of the
biodynamcially produced potatoes.
Dry matter content
There was a clear tendency for dry matter content to be higher in the
biodynamic treatment than in the conventional one in both the K-experiment
and in the two UJ-experiments. Dry matter content was significantly higher
in both B1 and B2 compared with the conventionally fertilized systems A1
Protein levels and protein quality
The level of crude protein was determined on the basis of Kjeldal-N,
whereupon the pure protein was precipitated with CuSO4 and NaOH and expressed
as per cent of the crude protein. In terms of crude levels of protein in
percent of dry matter a clear gradient was found from low levels in the
organically grown samples to high levels in the conventionally grown ones.
The crude protein content was also significantly higher in the inorganic
treatments in both UJ-experiments (figure 2), but the content of relatively
pure protein was significantly higher in the biodynamic treatments than
in the inorganic ones.
The content of the free amino acids was measured by titration with feromol
according to Sörensen. In the K-experiment the contents of these low
molecular-weight, non-protein nitrogen compounds were lower in the organic
treatment K1 than in K8 in all 19 studied years and lower in K1 than in
K7 in 13 of the 19 years during which this parameter was studied during
the experiment period. The higher protein quality of the organically grown
crops was confirmed by comparing the relative content of essential amino
acids and the biological value of protein, expressed as an EAA-index value
(Dlouhý, 1981; Pettersson, 1982).
Figure 2. Potatoes. Crude protein in percent of dry matter.
Darkening of tissue and extracts
The enzymatic darkening of raw, exposed potato tissue was measured
with a reflectance attachment on a photospectrometer (described by Pettersson
1982). The speed of darkening of potato-tissue extracts was measured photometrically
daily for four days at 530 nm. Both methods are described by Pettersson
and E. v. Wistinghausen (1979) and Pettersson (1982). In the K and UJ-experiments
both methods were used for evaluating the browning of the potatoes. The
darkening of extract was greater in K1 than in K8 in 18 of the studied
24 years and greater in K1 than in K7 in 17 of the years. The UJ-experiments
revealed that discoloration was more pronounced and developed faster in
the chemically-fertilized variants than in the organically fertilized ones,
and the difference was significant (P<0.01 in the UJ-experiments).
In this particular test of the resistance against the enzymatic and
bacterial decomposition in water extract (Rd/Ro = the maximum decrease
in the electrical resistance, in percent of the starting value in extract
dissolution 1:10 during 4-5 days, according to Pettersson, 1982), decomposition
values were generally lower for the organically grown variants than for
the others (24 of 24 studied years in K1 compared with K8 but only in 15
of 24 years in K1 compared with the K7). Differences similar to those obtained
between K1 and K8 were found in the comparison of conventional and biodynamic
treatments in the UJ-experiments (P<0.01 in the UJ-experiments).
Storage tests were conducted harvesting in? April in 20-kg bags. The
storage losses was measured in percent of the initial weight and included
losses through respiration and damage caused by storage fungi, etc. In
the K-experiment storage losses tended to be lower in the organic treatments
than in the inorganic ones (9 of studied 11 years). This difference was
even more pronounced in the UJ experiment at Järna and Uppsala (Figure
3) (P<0.05 and P<0.1).
Figure 3. Potatoes. Storage losses after 6-7 months in percent of original
Field survey of Phytophthora infestans
Frequencies of infection were significantly lower in treatments K1
and K2 (composted manure) and in K5 as compared with K8 ( high rate of
NPK), and K3 and K4 (raw manure) over the 14-year period during which this
parameter was studied. In the UJ-experiments the conventional treatments
were treated with fungicide, and the yield difference was highest during
the years with high infection levels (4 years).
Pathogen infection with Phytophora infestans (studied only during 1966-1969)
Although the spread of values was great with this testing method, a
similar trend in the results was, nonetheless, seen, with lower values
(i.e. less in vitro infection) in the organically grown samples than in
the conventionally grown ones.
Morphological methods. Morphology of stems
The number of horizontal stems did differ appreciably between treatments,
although values tended to be somewhat lower in the organic variants than
in the conventional ones (Pettersson, Brinton & v, Wistinghausen, 1979).
This negative correlation indicates that a low number of horizontal stems
corresponds with high product quality according to the index. The method
is described by Pettersson (1970). In the UJ-experiment at Järna (where
this method was also used) the number of side (horizontal) stems was significantly
lower in the biodynamic treatments.
As with the foregoing results, these tests (Engqvist, 1970; Pettersson,
1982) revealed a similar trend, with organizational traits in the tissues
being better in the organically grown samples than in the conventional
ones. In the K-experiment, this was true for all studied years between
1966 and 1989.
Influence of previous crop on the quality of potatoes
The effects of ley and barley on quality parameters of succeeding crops
differed in some respects. For example, potatoes following a ley tended
to show a higher degree of extract dissolution and to have a higher nitrate
content compared with potatoes following barley in the UJ-experiment. This
type of farming-system effect was not possible to study in the K-experiment
which was strictly a fertilization experiment.
Figure 4. Potatoes. K-experiment 1958-1989, UJ-experiment in Järna
1971-1979, UJ-experiment in Uppsala 1971-1976. Difference, in percent,
between the biodynamic treatments and the conventional ones for parameters..
Wheat in the K- and UJ-experiments
Average yield levels in K1 and K8 were nearly the same. For K2, in
which no biodynamic field preparation was carried out, the yield level
was significantly lower, and differences were highest during years with
a low yield level. In the UJ-experiments, with shorter experimental periods,
the yield levels were significantly lower in the biodynamic treatments.
In wheat as well, the crude protein content was higher in the inorganic
treatments in the K-experiment and in both UJ-experiments (Figure 5). However,
the content of relatively pure protein was higher in the biodynamic treatments
in the K-experiment and higher in the UJ-experiment at Järna (P<0.01
and P<0.1) That the protein quality was higher in the organic treatments
was also confirmed by the index for the essential amino acids (EAA-index,
Figure 5 a), which was significantly higher in the biodynamic manured systems
during the years when it was measured in the UJ-experiment.
Figure 5 a. Index of essential amino acids in the UJ-experiments.
Figure 5 b. Amylase activity in wheat in the UJ-experiments.
The resistance against extract dissolution
was also higher in the biodynamic treatments in these studies. In addition,
starch quality seemed to be higher in the biodynamic treatments, measured
in terms of falling number (in the K-experiment and the UJ-experiment in
Järna) and as indicated by amylograms (figure 5 b). The differences,
in percent, between the biodynamic treatments and the conventional ones
for quantitative and qualitative parameters for wheat are illustrated in
Figure 6. Wheat. K-experiment, 1958-1989, UJ-experiment in Järna,
1971-1979, UJ-experiment in Uppsala 1971-1976. Difference, in percent,
between the biodynamic treatments (K1) and the conventional ones (K8) for
quantitative and qualitative parameters for wheat.
Final discussion concerning the significance of the studied
Correlation between crude protein content and other parameters
In the UJ experiment at Järna significant correlations were observed
between crude protein content and most of the studied parameters in both
potatoes and wheat (Pettersson, 1982). For potatoes this parameter was
correlated with dry matter content (negative, P<0.001), relatively pure
protein (negative, P<0.01), EAA-index (negative, P<0.001), ascorbic
acid content (negative, P<0.001), cooking quality (negative, P<0.01),
taste quality (negative, P<0.001), free amino acids (positive, P<0.001),
extract dissolution (positive, P<0.001) and darkening of extract (positive,
P<0.001). For wheat, the correlations were with EAA-index (negative,
P<0.01), extract dissolution (positive P<0.001) falling number (positive
P<0.05), gluten content and baking tests (positive, P<0.01). It
can thus be concluded that cereals with a high crude protein content, which
is generally desired by the baking industry, tend to rank low in terms
of biological and physiological quality parameters. Similarly potatoes
with a high crude protein content tend to rank low in terms of biological
and physiological quality parameters and taste.
Light and shade
The studied parameters were divided into three groups: chemical/biological,
physiological and a third called morphological. Parameters falling into
the last-mentioned group has been studied through a method based on observations
of the morphology of stems in potatoes and a picture formation method (Crystallization
with CuCl2). It was assumed that the lower quality of the crops, assessed
in terms of these parameters studied here, in the conventionally fertilized
systems is similar to what would have been found had the plants been grown
under more shaded conditions. Likewise, the higher biological value of
the protein and the higher values found for quality parameters are similar
to what would have been expected had the plants been grown under full light.
In the interpretation, the organic treatments are described as having the
same effect as an increase in solar radiation, and likewise, the effects
of NPK-treatments are analogous to those induced by an increase in shade
The better protein composition, with a lower content of free amino
acids, and better storage properties were attributed to the higher organization
level resulting from the organic and biodynamic fertilizing systems. The
higher "organization level", reflected in the higher biological
value of the protein and lower content of free amino acids not used in
protein synthesis, was correlated with better resistance against pests,
less darkening, less extract dissolution and lower losses of potato during
storage. Future research should be aimed at improving our understanding
of the significance of these qualitative values in terms of their effects
on the human health.
Upon completion of the K-experiment, a new experiment was begun in
both Sweden (1992) and Finland (1995) in which different manure systems
were compared in connection with various types of crop rotations on organic
farms. The aim is to gain a better understanding of the differences between
composted, non-composted and liquid manure in terms of their effects on
the parameters discussed here and to develop effective methods for regularly
testing product quality. In addition, the biodynamic preparation treatments
are being studied so that their effects can be predicted more reliably.
Preliminary results from studies in potatoes in Finland indicate that the
use of liquid manure, like mineral fertilizer, tends to decrease the biological
value. The ultimate goal is to tailor the fertilizing regime to the soil,
climate and crops in a way that offers both a good yield an a healthy product
with a high nutrient value.
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