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Drought and soil acidity are two major abiotic stress factors limiting maize production worldwide, generating imbalances in the manganese (Mn) and zinc (Zn) status in plants. This study was conducted to determine the effects of drought stress on the Mn and Zn status in maize genotypes grown on acid and non-acid soils and how the Mn and Zn status affects the changes in grain yield caused by drought stress and soil acidity. Seventeen genotypes were grown at two locations differing in soil acidity in Eastern Croatia in 2003 and 2004. Positive values of an aridity index indicated drought stress in 2003. The genotypes had much higher Mn and Zn concentrations on acid soil than on nonacid soil: more than twice as high in both seasons for Zn and about 6 and 9 times higher in normal and in dry seasons, respectively, for Mn. This demonstrates that drought combined with soil acidity led to the excessive accumulation of Mn in maize plants. However, variation was observed between the maize genotypes for the Mn accumulation on soils differing in acidity when drought occurred. Some genotypes accumulated Mn on acid soil irrespective of drought. The Mn and Zn status had no discernible effect on the changes in grain yield caused by drought stress and/or soil acidity.

Five maize (Zea maysL.) hybrids were grown for four growing seasons on gleysol characterized by moderate supply with potassium (K). Three rates of KCl were applied in four replicates at the beginning of April 2001 as follows (kg K 2O/ha): 150 (control), 650 and 1400. The highest rate of KCl resulted in significant increases of yield of 14%, 24% and 12%, for 2001, 2002 and 2003, respectively; while in the fourth year similar yields to the control were found. The OsSK552 and Bc5982 hybrids (4-year mean 8.70 t/ha) were more susceptible to soil stress in comparison with OsSK444 and OsSK458 (mean 9.07 t/ha). At the same time, Florencia hybrid yielded 9.37 t/ha. Four hybrids responded similarly to applied fertilization (yield increases from 13 to 16% in comparison to the control), while Florencia had low response to KCl (yield increase for 5% only). Under these conditions we recommend combined solution using 1000 kg K 2O/ha every third year and a choice of tolerant hybrids.

Aim of this study was testing of field crops (maize-maize-sunflower-winter barley rotation) to lime (carbocalk: waste of sugar factory, 39% CaO) application in five rates up to 90 t/ha. Field trial was conducted in autumn 2000 in four replicates. Liming with carbocalk resulted with considerable increases of field crop yields as follows: up to 50% and 36% (maize for 2001 and 2002, respectively), up to 49% (sunflower 2003) and up to 30% (barley 2004). In general, by application of carbocalk to level of 90 t/ha, yields drastically decreased mainly to level of control as affected by over liming. Concerning oil contents in sunflower grain, it was significantly higher compared to control for treatments 15, 30 and 45 t/ha, but similar for control and 60 t/ha. Using of 45 and more lime per hectare decreased grain quality of malting barley because protein contents were significantly increased.

Increased rates of P and K (monoammonium phosphate and potassium chloride) were applied in four replicates on two soils in spring 2001 as follows: a) standard fertilization (kg ha1: 177 N + 100 P205+ 150 K20); b) a+ 1500 kg P205ha"1; c) a + 1500 kg K20 ha-1; d) = b + c. Residual effects of the fertilization were tested in the next year. Maize (OsSK552 hybrid) growing on Luzani soil resulted in 15% lower yield compared to the Kobas soil (7.75 and 9.06 t ha-1, respectively). Mean the leaf (the ear-leaf at silking) concentrations (mg kg-1) were 41.8 (Zn), 14.1 (Cu) and 131 (Fe), respectively. The leaf Mn was by 60% lower and the leaf Zn by 16% higher in 2002 compared to 2001. Maize grown in the Luzani trial had by 9%lower the leaf Zn, 10% lower the leaf Cu and by 37% higher the leaf Mn compared to the Kobas soil. Under the influence of P fertilization, the leaf Zn decreased by 37% compared to the control. Application of both P and K resulted in decreases of leaf Zn by 30%. However, P fertilization, alone or in combination with K, increased the leaf Mn for 111% and 72% respectively. Significant difference the leaf Cu (by 9% lower) was found under influences K fertilization only. The leaf Fe was independent on these factors.

The field experiment with three rates of phosphorus (P) fertilization for maize (OsSK444 and OsSK552 hybrids) up to 2000 kg P2O5/ha were conducted in the spring 2002. For the next growing seasons (2003 and 2004) only ordinary fertilization was applied. In general, maize yields were independent on applied fertilization. Only application of the highest P rate had residual influences on maize yields for the 2003 growing season. Probably very favorable weather conditions for 2002 and 2004 could be resposible factor for low influences of fertilization on maize yields. Also, maize hybrid OsSK552 yielded more than OsSK444. The ear-leaf of maize at beginning of silking (the 2002 growing season only) was taken for chemical analysis. Leaf P, Mg, Mn and Fe concentrations increased by application of the highest rate of P. At the same time, K, Ca, Zn, Cu and Fe concentrations significantly decreased. Especially influences of P fertilization were found for Zn status in maize leaves (70 and 40 ppm Zn, for the control and 2000 kg P2O5/ha, respectively). OsSK552 hybrid characterized by the higher K, Ca, Mg, Cu and Fe, as well as the lower Zn concentrations in comparison with the OsSK444 hybrid.

Twenty corn (Zea maysL.) hybrids were grown under the field conditions during the 2000 and 2001 growing seasons. The ear-leaf at the beginning of the silking stage was taken for chemical analysis. The experimental fíeld was acid hydromorphic soil with moderate levels of mobile fractions of magnesium (Mg), calcium (Ca) and phosphorus (P). In our testing considerable influences of growing season (mean 0.273 and 0.177 mg Mg/kg, for 2000 and 2001, respectively) and heredity (range of 2-year means among the 20 hybrids: from 0.120 to 0.291 mg Mg/kg) were found. Three corn hybrids (OsSK395, RK1456 and OsSK332) had low Mg (<0.2000 %Mg) concentrations in both growing seasons (means 0.177 and 0.138 % Mg, for 2000 and 2001, respectively). Four other hybrids (OsSK277, OsSK2-91, OsSK247 and OsSK234) had adequate Mg status (means 0.297 and 0.228 %, for 2000 and 2001, respectively). Grain yields of the hybrids ranged from 4.06 to 11.691 ha-1. Six hybrids yielded less than 7 t hal(Alpos, OsSK2-191, OsSK247, Bc278 and Clarica: mean 5.491 ha-1. Yields of other three hybrids were above 10 t ha-1(OsSK378, OsSK298 and OsSK277: mean 10.91 t ha-1). Mean yields of two hybrid groups differing in Mg status totaled 8.60 and 7.521 ha-1, for the low Mg-group and high Mg-group, respectively. Although Mg status in soil and plant was mostly either moderate or low, correlation coefficients between the yield and Mg status were low under these conditions.

Maize (OsSK552 hybrid) was grown under field conditions on two hydromorphic soils of moderate fertility for two growing seasons. Increased rates of P and K (monoammonium phosphate and potassium chloride) were applied as follows: a) control (standard fertilization); b) a + 1500 kg P2O5ha-1; c) a + 1500 kg K2O ha-1; d) = b + c. Residual effects of ameliorative fertilization were tested in the following year (2002) and the experiment was fertilized uniformly (kg ha-1: 177 N + 100 P2O5+ 150 K2O). The treatments were laid out according to the randomized block scheme with four replications. At the beginning of the silking stage, ear leaves were taken for chemical analyses. Maize growing on Luzani soil resulted in 15% lower yield compared to the Kobas experiment (7.75 and 9.06 t ha-1, respectively). Fertilization had a significant influence on the nutritional status of maize. For example, in comparison with the control, under the influence of P fertilization leaf P, Ca and Mg increased by 25%, 20% and 22%, respectively, while leaf Mg decreased by 10%. K fertilization decreased leaf Mg, Ca and P by 30%, 13% and 7%, respectively, while leaf K increased by 16%. Application of both P and K resulted in increases of leaf P and K by 14 and 15%, respectively, while leaf Ca and Mg decreased by 5% and as much as 30%, respectively.

Fifty four corn inbred lines of different origin were grown for one year on the selection field (eutric cambisol on calcareous loess substrate; pH in H2O=7.8, humus content=1.8%). Each inbred line was grown in a 6.3 m row (20 plants/row). The ear-leaf Fe (the tasseling stage) was widely different. For example, when the highest value waas designated as 100, the highest value “was 21 and 28 for FAO groups 500 and 600, respectively.The general combining ability of corn inbred lines was estimated by means of mean grain yield of their single cross hybrids. It also ranged widely: from 7.45 to 11.57 t/ha. However, under environmental conditions of testing, the connection between the ear-leaf Fe and the general combining ability of corn inbred lines was low (r=0.12 and r=-0.30 for FAO group 500 and 600, respectively).

In certain applications, a reinforced composite is used as an adhesive layer. In this study, the bulk mechanical behaviour of composite films based on a poly(vinyl acetate) (PVAc) matrix and various calcium carbonate (CaCO3) fillers was investigated. The interactions depend on the morphology and chemical structure of the filler and the polymer matrix. The polar natures of both PVAc and CaCO3have a strong influence because of acid-base interactions. The tensile properties of PVAc/CaCO3composites showed an increase in strength at break with increased filler concentration. The interactions can be modified by surface pretreatment of CaCO3with stearic acid, which lowers the surface interaction and changes the degree of filler dispersion in the PVAc matrix. Micrographs confirmed the tendency of small CaCO3particles to agglomerate and as a consequence, discontinuity of the composite film is observed. An effective surface treatment reduced the particle agglomeration tendency, which improved the film elongation at break. Quantitative determination of interactions was made by using various theoretical and empirical models which describe the composite mechanical behaviour dependence on the filler volume fraction.

The properties of poly(vinyl acetate) compositions prepared as potential wood adhesives were investigated. The paper presents the results of the influence of various kinds of inorganic fillers based on calcium carbonate and alumino-silicate and an organic filler, starch, on the adhesive composition properties. The comparison among rheological behavior of the adhesive dispersions concerning the specific role of fillers were made. Mechanical and relaxation properties of the adhesive films could reveal the effect of filler characteristics on the polymer matrix. The significant influences of particle size distribution and specific surface area on the poly(vinyl acetate) adhesive composition were determined, along with other filler characteristics.

The influence of liming and phosphorus application (in the range to 20 t of hydrated lime and to 480 kg P2O5/ha, respectively) on the status of plant available Fe was studied in acid soil of East Croatia. Due to application of the highest rate of line, Fe content in soil decreased from 34.1 ppm (unlimed plot) to 14.1 ppm Fe. At the same time, titratable acidity decreased from 16.0 to 1.5 raequ/100 g of soil and exchangeable acidity from 3.0 to 0.1 mequ/100 g of soil, while soil pH in KCl increased from 4.03 to 5.42. Phosphorus application did not significantly affect these soil characteristics.

Disorders of corn growth were observed at 6-9 leaf stage in the growing season of 1986. They were manifested as growth retardation and chlorosis. Chlorotic corn showed signs of either P, Zn or K deficiency. Excessive Fe and Al uptake in the leaves (4.7, 3.1, 1.9 and 2.2 times higher Fe concentrations than in normal plants for chlorosis induced by P, Zn and K deficiency and in the cases of atypical chlorosis, respectively). Depending on the form of chlorosis, the dry matter of chlorotic plants was 4.6 to 10 times lower than in normal plants.