According to the above described method aft er site
preparation (delivery of clean and contaminated soils from
the area in the vicinity of the pipeline rupture location)
the plant growth experiment was set up. Those treatments
were were included where the changes were expected, both,
in the soil (basic chemical properties, metals, oils, PAHs),
and in the crops grown (chemical composition of plant
material, crop establishment and yield achievment).
The data presented in this paper show slight, barely
present chemical heterogeneity of the soil (Table 1). Soil
reaction is low acid to neutral in all samples, and varies in
the range from pH 6.42 to pH 7.13. Th ese values indicate
that soil reaction values are not signifi cantly aff ected by
varying quantities of hydrocarbons in the soil. However,
this is not the case with the organic matter content in the
soil. Th e soil taken from the site outside of the rupture
location, the one which was not aff ected by oil well operations
has lower organic matter content (treatments 1; 7
and 8). In all other treatments the organic matter content
is higher, or it was increased consistent with the increase
in the content of oil i.e. hydrocarbons in the soil. For that
reason, we fi nd it not surprising that the highest organic
matter content has been found in completely contaminated
soil taken from the contaminated soil disposal site at the
Števkovica-4. The presence of available phosphorus and
potassium in the soil is high, which can be attributed to
fertilization carried out in plant growth experiment.
The crops being investigated include: winter wheat
(Triticum aestivum L.) which was sown on 14 October 2003
and 26 October 2005 respectively, winter barley (Hordeum
vulgare L.) sown on 21 October 2004 and soybean (Glycine
hyspida L.) sown on 29 June 2005 and 3 July 2006 respectively.
Sowing standards applied in these investigations comply with standards for these crops sown in natural field conditions.
Crop establishment recorded, which will be probably
be confi rmed by yield achieved, indicates that oil contaminated
soil was crucial factor in the decrease of crop establishment,
and consequently number of plants and yield
reduction. By the similar results in their research reached:
Gogoi et al., 2003; Maliszewska-Kordybach and Smreczak
2003; River-Espinoza and Dendooven 2004. Judging by recorded
crop establishment, the diff erences in yield achieved
are expected, as shown in the tables 2, 3, 4 and 5.
During the first year of research, in winter wheat crops
(variety - Zlatni dukat), in the very stages of germination
and emergence, diff erences in crop emergence were observed
depending on the diff erent content of hydrocarbons
in the soil. Emergence of plants being investigated was
inversely proportional to the crude oil content of soil. In
the treatments with signifi cantly more contaminated soil
(treatments 2, 4, 7 and 8) emergence recorded was lower
relative to the treatments with less hydrocarbon or oil contaminated
soil (Table 2). It is clear that a thin oil coating
is formed around the germ thus preventing oxygen infl ux
and causing death of the seed and/or slower emergence of
the future plant. If an optimum number of plants would
have been the one recorded in the check treatment(100%),
then in contaminated soil 74% plants crop establishment
was recorded; in treatment 3: almost 100%; in treatment
4: 60%; in treatment 5: 88% plants; while in treatment 6,
crop establishment was only 50% plants. On the two remaining
treatments crop establishment were 57% and 37%
plants respectively. Yield achieved on check treatment was
statistically higher relative to the other treatments, but no
statistically signifi cant diff erences were found between the
other treatments.
During the second year of investigation winter barley
(variety – Rex) was sown in pots. In the very beginning
of crop emergence diff erences were observed relative to
the fi rst year of research when the wheat was sown. In the
second year crop emergence was rather uniform and that
which trend continued throughout the growth process.
The number of plants recorded and crop establishment
achieved show no diff erences that were observed during
the fi rst year. Based on the established number of plants no
statistically signifi cant diff erences were noticed. However,
yield achieved indicates statistical diff erences, but less
striking than in the fi rst year. Th e greatest diff erence was
recorded between the check (treatment 1) and contaminated
soil (treatment 2), while other treatments had more
or less uniform yield (Table 3).
After barley was removed from the pots, soybean was
sown (cultivar Sabina: 00-000 maturity group). Crop establishment
and yield show very interesting changes relative
to the previous year. As usual, sowing standard for all
treatments and all pots was the same. However, in the early emergence stage and also during the growth cycle significant diff erences were observed in crop establishment and
yield achieved. Th roughout the growth cycle the largest
number of plants was recorded with the check treatment,
while with other treatments the established number of
plants varied (Table 5). By far the worst crop establishment
was found with treatment 6, and with other treatments
it was signifi cantly lower than with the check treatment.
Th e highest yield was recorded with the check treatment;
while with others, yield was signifi cantly lower. Although
the experiment was commenced three years ago, it can be
noticed that oil contamination even then had signifi cant
eff ect on the number of emerged plants and, accordingly,
crop establishment of soya.
In order to make a comparison with the fi rst year of
research when winter wheat was sown in pots, this crop
(the same variety – Zlatni dukat) was sown again in 2005.
In the early emerging stage signifi cant changes could be
noticed in crop establishment achieved relative to the fi rst
investigation (Table 4). As in the fi rst year, around 200
viable seeds per pot were sown and wheat establishment
varied from 70% with the check treatment to 50% with the
soil completely contaminated with oil. During the earing
up stage almost similar percentages were recorded. If establishment
achieved with the check treatment is taken as
optimum establishment in the earing up stage then 70%
establishment achieved could be noticed with contaminated
soil (treatment 2), 95% establishment with treatment
4, and with all other treatments crop establishment was
around 90% of the optimum establishment achieved with
the check treatment.
Knowing that in the first year of research when the
same crop of the same type was in the pots, the establishment
with some treatments was only 30% of the optimum
establishment, the diff erences recorded this year are not
considered to be statistically signifi cant, except treatment 2
where was recorded lower number of plants. In correlation
with check treatment the treatment where crude fresh oil
was used yield was signifi cantly smaller (Table 4).
In the latest year of research presented in this paper
(in autumn 2006 barley variety Rex was sown again in
pots), in July 2006 the soybean was sown again, but this
time another cultivar – Dora: 0-00 maturity group. In
relation to 2005 when soybean type Sabina was sown in
pots, this year, crop establishment (the number of emerged
plants) was signifi cantly diff erent. This requires clarifi cation
of the diff erence in the number of emerging plants
with the check treatment in these two years when in both
cases the soybean was sown in the pots. Sabina is a type
of soybean which is sown with higher target plant population:
1.400.000 plants per hectare, while Dora is a type
which is sown in the target plant population of 650.000
plants per hectare. This accounts for the diff erence in the
number of emerged plants. However, based on recorded
crop establishment, it can be assumed with a great degree
of probability that these diff erences will not be great or
statistically signifi cant (Table 5).
The presented results of three-year research and growth
of fi ve crops indicate that incidents caused by various oil
well operations result in soil changes and changes in the
plant material or yield. Similar conclusion results in their
research bring forth: Riser, 1998; Rhykerd et al., 1999; Maila
and Cloete, 2005; King et al., 2006; Osuji and Onojake,
2006. The changes are particularly noticeable during the
first year followed by the obvious decrease in changes
in the following years. Similarly, the diff erences in yield
and crop establishment between stubble crops and spring
crops were observed. Since these are investigations of plant
growth in pots, all doubts arising out of such research will
be addressed in the three-year field research yet.
Thanks to financial contribution of INA Exploration
and Production and to an international European project
“Development of Programme for Constant Monitoring of
Croatian Soils Including the Pilot Project – LIFE05 TCY/
CRO/000105” a field project (near Nature Park Lonjsko
polje) was set up using very similar methodology.
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