Joint International Conference on Long-term Experiments ...

humanity organization, in cooperation with Croatian Co-operative Association and
Croatian Agricultural Extension Service, in frame of ECRA project – revitalization of
war affected communities- which are supported by USAID agency, began education of
farmers in Djulovac (Bjelovar-Bilogora County), Pakrac (Pozega-Slavonia County) and
Okucani (Brod-Posavina County) municipalities. During March of 2003 total 108 soil
samples (0-30 cm depth) were taken form unfertilized fields (total 279 ha) and soil
testing was made (soil pH, plant available phosphorus and potassium according ALmethod).
About 60% of tested soil samples (total 65) were acid ( pH in KCl less than 5)
and liming could be useful. Also, about 40% (total 42) of soil samples were poor or
moderate supplied with phosphorus, while potassium status is better because only 13%
samples (total 14) were in this range of K availability. These results were in detail
elaborated in the previous study (Kovacevic et al., 2005). Soil test was criterion for
choice of the plots for field experiments with increased fertilization with P and K
including Korenicani experiment in Bjelovar-Bilogora County. Grain yields of maize in
this experiment for three-year period were elaborated in detail by the previous study
(Kovacevic et al., 2006). In this study, influences of the fertilization on leaf and grain
composition were shown.
MATERIAL AND METHODS
The field experiment: Four fertilization treatments by application of NPK 7:20:30
fertilizer (the product of Petrokemija Fertilizer Factory Kutina, Croatia: a = 0 = standard
fertilization, b = a+1250, c = a+2500 and d = a+3750 kg ha -1 ) were applied on
Korenicani soil (municipality Djulovac, Bjelovar-Bilogora County). Different amounts
of nitrogen (N) for the a-d treatments were equalized by addition of CAN (calcium
ammonium nitrate) in the amounts 974, 649, 325 and 0 kg ha-1, for the a, b, c and d,
respectively. Only standard fertilization of the experiment for the 2004 and the 2005
growing seasons were applied. The experiment was conducted in four replicates by
randomized block design. Gross of the basic plot was 92,4 m 2 (11.0 m x 8.4 m). Maize
hybrids OsSK552 (the growing seasons 2003 and 2004) and OsSK499 (the growing
season 2005) were sown by pneumatic sowing machine in terms end of April/beginning
May. Planned (theoretical) plant densities (TPD: plants ha -1 ) were 51948, 54 946 and
57143, for 2003, 2004 and 2005, respectively. Maize was harvested manually (four
rows from each plot). Grain yiels were calculated on 14% grain moisture basis and plant
densities as follows: 90% TPD (2003), 70% TPD (2004) and 95% TPD (2005),
respectively.
Sampling and chemical analyses: Soil samples were taken after maize harvest at end
October 2005. The samples were taken by auger to 30 cm of depth (15 individual
sampling in the mean sample). The ear-leaf of maize was taken at beginning of silking
(middle of July; 25 leaves in the mean sample). Soil, leaf and grain sampling were made
from three replicates of the trial.
Nutritional status of soil (mobile fraction of the elements) was predicted by
extractions with NH4Acetate + EDTA (pH 4.65) according Lakanen and Ervio (1971)
and their determination by the ICP-AES procedure. For general soil test AL-extraction
was used (Egner et al., 1960). Soil reaction and organic matter were determined
according to ISO (1994, 1998). The total amounts of the elements in the leaf and grain
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