Vladimir Vukadinović

Relationships among Chloroplast Pigments Concentration and Chlorophyllmeter Readings in Soybean under Influence of Foliar Magnesium Application

The influence of foliar magnesium (Mg) application before flowering on chloroplast pigment indices was investigated in a 2‐year field experiment with five soybean cultivars. Acetone extraction of pigments (chlorophyll a and b, total chlorophylls, and carotenoids as well as their ratios) was compared to chlorophyll meter (SPAD‐502) readings. The untreated plants showed significant influence of cultivar on pigment concentrations, and pigment ratios were year‐dependant. Foliar fertilization with Mg influenced chlorophyll concentration mostly in the year 2004, and carotenoids were not altered by Mg treatment. Cultivar differences prevailed in the next year when Mg treatment was less effective. The interactions among year, cultivar, and Mg application were showed to be significant for a particular parameter. The SPAD‐502 readings significantly correlated with pigment concentrations only in the untreated plants in 2005. However, the foliar treatment influenced significantly SPAD readings in 2004, through the interaction with cultivar in once‐treated plants and as a single factor in twice‐treated plants. Grain yield was under significant positive influence of leaf Mg concentration in both years, and one treatment with Epsom salt was enough for significant grain yield increase.

Winter wheat yield responses to mineral fertilization

The yield of arable crops may be influenced by many factors such as water, temperature and nutrient deficiency. The winter wheat (variety Zitarka) field trials were set up in the autumn of 2002 on silty loam stagnic luvisol at site Donji Miholjac and loessive pseudogley at site Krizevci in continental Croatia. The results of the triennial experiments show big influence of climate conditions (year) and sites on usage of nutrients from fertilizer and forming of wheat yield. The highest fertilization dosage (N5P2K2) in average almost doubled the total mass yield and wheat grain yield comparing to the control. Fertilization with nitrogen, which according to the phosphorus input in average increased the grain yield 3.5 times and above ground mass yield 10 times, and according to the potassium 4 and 20 times, had the biggest influence on both yields. Non appropriate fertilizer use may result in non sustainable plant nutrition.

Mineral composition of alfalfa ( Medicago sativa L. ) as influenced by liming and manure application

The objecive of this research was to assess the mineral composition of alfalfa grown on a pseudogley soil limed with carbocalc (byproduct of sugar factory, containing 70.5% CaCO3) and/or enriched with organic matter by cattle manure application. Nitrogen, phosphorus, potassium, magnesium, calcium, iron, manganese, zink and copper concentration were analysed in two cuts of alfalfa, grown on acid soil for three consecutive years (2002-2004).It was concluded that liming and manure application had highly significant influence on mineral composition of alfalfa, preventing possible toxic concentrations of heavy metals. Such soil amendments enable growth of this important crop on less favorable, acid soil through soil pH adjustment and regulation of plant nutrient availability, whereas plant mineral composition can differ significantly seasonally.

Comparability of Electroultrafiltration and Ammonium Acetate-Lactate Extraction Data for Phosphorus and Potassium in Pseudogley Soils

The aim of this research was to compare two standardized soil extraction methods [electroultrafiltration (EUF) and ammonium acetate–lactate (AL)] regarding potassium (K) and phosphorus (P) availability in pseudogley soils. In total, 60 pseudogley soil samples from 12 agricultural sites in eastern Croatia (each represented by five soil samples—replicates) were simultaneously analyzed by both methods. The relations of K and P with other important soil traits [pH, selective mineral clay content (SMC), humus content] were established by multiple regression analyses. Furthermore, a highly significant regression equation (P ⩽ 0.01) was established for AL–phosphorus pentoxide (P2O5), using EUF‐P‐I and EUF‐P‐II separately as well as soil pH value determined in 1 M KCl as independent variables. The actual P amount extracted by AL differed by 9% from the value predicted by the regression function. According to the highly significant multiple regression function (P ⩽ 0.01), AL‐extractable dipotassium oxide (K2O) can be approximated using EUF‐K (sum of EUF‐K‐I and EUF‐K‐II fraction), SMC, and the EUF‐K‐Q (ratio of EUF‐K‐II and EUF‐K‐I) as the independent variables. A deviation of calculated AL‐K2O value from the extracted amount of K was 4%. These results point out the possibility of the comparison of EUF and AL extraction data in the evaluation of K and P availability in pseudogley soils. The necessity of more comprehensive research regarding the comparison of the EUF and AL method, taking into account plant nutrient acquisition specificity and a great number of interrelated soil and climate factors, was suggested.

Liming of acid soils in Osijek-Baranja County.

The negative trend of soil degradation process increases with intensive agricultural production. Therefore, there is a need for soil conditioning like liming, humification, fertilization, etc. to improve soil quality. One of the major problems that occur on agricultural soils of Croatia is acidification. A downward trend of soil pH is mainly present in soils of poor structure with intensive agricultural production. In agricultural practice liming often needs to rely only on the pH value, without determining the hydrolytic acidity, CEC or soil texture. Due to the above mentioned facts, calculation of liming for Osijek-Baranja County was conducted with the help of ALRxp calculator, which takes CEC, soil pH in KCl, hydrolytic acidity, bulk density of soil, soil textural class and depth of the plow layer to 30 cm into account. Low soil pH values have a great influence on soil suitability for crops as well as on the deficit of calcium and magnesium. All of these lead to the degradation of soil structure, and can even lead to disturbances of plant nutrition in some production areas. On such soils, liming would be imperatively required, but with caution because an excessive intake of lime materials, especially without the necessary analysis, causes a decline in organic matter and reduces accessibility for plant uptake of microelements.

Organic phosphorus in acid and calcareous soils in continental part of Croatia

Maize (Zea mays L.) genotypes wit It improved nitrogen utilization efficiency (NUE) are of interest to growers. Field experiments were conducted to evaluate the total N uptake in the aboveground biomass and NUE (kg grain per kg of N absorbed in the aboveground biomass). Four commercial hybrids of similar maturity ranking were grown under the high-N (200 kg N ha(-1)) and low-N (1100 kg N ha(-1)) fertilization rates over three years. Growing conditions significantly affected hybrid performance for NUE, which ranged from 42 kg grain kg N-1 in the low-yielding (dry) environment to 55 kg grain kg N-1 under higher yielding environment, When compared to the low-N rate, the average N uptake was by 32% higher at the high-N rate, whereas smaller differences occurred for the aboveground biomass (12%), grain yields (14%), stover N (28%) and grain N (13%) concentrations. Significant differences existed among tested hybrids for grain yield, aboveground biomass, grain and stover N concentration, N uptake and consequently NUE.Hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnatum L.) were evaluated as cover crops during two vegetation seasons in the Mediterranean and Continental area of Croatia. Better tolerance to low winter temperatures was observed for crimson clover. Higher plants (10 to 3 1 cm) before winter and in spring (67 to 117 cm) were measured for hairy vetch, while crimson clover had higher yields of fresh biomass (33.7 to 113.1 t ha(-1)). Concentrations of N (1.53 to 3.34%), P2O5 (0.55 to 1.04%) and K2O (2.02 to 5.32%) in plant tissue were higher for hairy vetch. However, due to higher yields of dry matter, crimson clover accumulated more N (105 to 239 kg ha(-1)), P2O5 (28 to 83 kg ha(-1)), and K2O (105 to 440 kg ha(-1)) than hairy vetch. According to our results crimson clover could be recommended as a cover crop in Mediterranean and Continental area of Croatia.

Potassium fixation in heavy soils of east Croatia

Bioavailability of potassium is strongly affected by present alkaline earth ions Ca and Mg and fixation of potassium into interlayer zones of some clay minerals. Soil fixation ability strongly affects the efficiency of fertilization. The research has been conducted on 6 hydromorphic and gleysoils in eastern Croatia. Soil fertilization with 450-4500 kg ha-1 K2O was simulated in lab-conditions. After one day the samples were extracted with NH4OAc 6 times, shaked, centrifuged and transferred into flasks. Fixation of potassium was calculated according to the formula: Kf = Ka – Ke + Ko, in which Kf is fixated K2O in mg 100g-1 soil ; Ka is K2O added as fertilizer in mg 100g-1 ; Ke is K2O determined in the eluate and Ko is K2O in the sample without fertilization. Fertilizing simulation of heavy soils in eastern Croatia with medium or very high dosages of potassium (450-4500 kg ha-s ; ), deducted in lab-conditions, showed that AL method of potassium extraction gives relatively high values of available potassium (two times higher than extraction in NH4OAc). Also, highest relative amount of potassium is fixated at lower fertilizing dosages (approximately 76%), the increase in fertilization increases absolute, but reduces relative fixation. Some heavy soils have high ability of fixation (above 70-90%) and very low desorption, and require special attention when establishing dosages for fertilization and ameliorative fertilization with potassium. Results obtained by soil analyses show connection between high fixation of potassium added by fertilization and higher amount of clay in the soil as well as lower level of available potassium before fertilization.

Extractants testing for determination of plant available manganese in soil

Various extractants have been used in determining plant available manganese in soil but critical comparisons among them are lacking. In our experiment, 14 extractants were tested using soil of three types (chernozem, pseudogley and humogley) from six locations. Neubauers bio test was used for evaluating capacity of extractants to determine plant-available Mn. Total Mn content in soil was in range 195–520 mg kg-1. Depending on the extractants used, 4–41% of total soil Mn was extractable. The lowest value of extractable Mn was obtained in CH3COONH4 (1 M) and the highest in EDTA (0.05 M). Statistically significant correlations between the biological test and chemical extraction were obtained for seven extractants tested: EDTA (0.05 M), HCl (1 M), H2SO4 (0.5 M), CH3COOH (0.4 M), H3PO4 (0.033 M), DTPA/CaCl2/TEA (0.005 M/0.1 M/0.1 M) and EDTA/(NH4)2CO3 (0.01 M/1 M). The most suitable extractants based on relationships between available soil Mn and Mn content in plants were 0.4 M CH3COOH and EDTA/(NH4)2CO3 for acid and alkaline soils, respectively.

Response of maize (Zea mays L.) to soil stress and to P and K fertilization on strong K-fixing soil

Strong K fixation, alone or in combination with P deficiency, is a limiting factor of maize (Zea mays L.) production on some gleysols of eastern Croatia. In comparison to maize yields in the control treatment (3.8 t ha-1), yields were increased by 87 and 42% with the highest level of K (2.1 t K ha-1) and P (1.1 P t ha-1) fertilization, respectively. At the same time, the ear-leaf K and P status (on dry matter basis) was increased from 0.70 (acute K-deficiency) to 1.74% K, and from 0.28 to 0.48% P. Improvement of plant K status resulted in a decrease in ear-leaf Mg from 1.46 to 0.73% Mg. Maize genotypes differed in tolerance to K and P deficiencies. Based on our testing of 14 corn hybrids under deficiency conditions, grain yield of the most susceptible hybrid (2.5 t ha-1) was about 50% lower in comparison with the most tolerant hybrid. Maize hybrids showed tolerant of soil K and P deficiency are viable management options on K-fixing, P-deficient gleysols in eastern Croatia.