Zdenko Lončarić

Influences of fertilization on yield and nutritional status of maize

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 ha-1: 177 N + 100 P2O5 + 150 K2O) ; b) a + 1500 kg P2O5 ha-1 ; c) a + 1500 kg K2O 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.

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.

Response of Lemna minor L. to short-term cobalt exposure: The effect on photosynthetic electron transport chain and induction of oxidative damage

The effect of two concentrations of cobalt (Co(2+)) on photosynthetic activity and antioxidative response in Lemna minor L. were assessed 24, 48 and 72h after the start of the exposure. Higher concentration of cobalt (1mM) induced growth inhibition while lower concentration (0.01mM) increased photosynthetic pigments content. Analysis of chlorophyll a fluorescence transients revealed high sensitivity of photosystem II primary photochemistry to excess of Co(2+) especially at the higher concentration where decreased electron transport beyond primary quinone acceptor QA(-) and impaired function of oxygen evolving complex (OEC) was observed. Due to impairment of OEC, oxygen production was decreased at higher Co(2+) concentration. Activity of superoxide dismutase was mainly inhibited while lipid peroxidation increased, at both concentrations, indicating that cobalt-induced oxidative damage after short exposure and moreover, susceptibility of the membranes in the cell to cobalt toxicity. Results obtained in this study suggest possible application of used parameters as tools in assessment of early damage caused by metals.

Water extractable concentrations of Fe, Mn, Ni, Co, Mo, Pb and Cd under different land uses of Danube basin in Croatia

Abstract Water extraction of trace elements can simulate the concentration of elements in the soil solution from where the plant takes up the elements. The objective of this investigation was to determine the water extractable concentration of seven trace elements (Fe, Mn, Ni, Co, Mo, Pb and Cd) and to assess their relationship with soil properties of the Danube basin in Croatia. Soil samples from the surface layer (0–25 cm) of 74 sites, having different land uses (forest and agricultural land), were collected. Samples were analysed for total and water extractable trace elements as well as for pH, DOC, SOC and CEC. The concentrations of water extractable fraction of trace elements were on average: 20.14 mg kg−1 for Fe, 3.61 mg kg−1 for Mn, 0.07 mg kg−1 for Ni, 0.016 mg kg−1 for Co, 0.01 mg kg−1 for Mo, 0.01 mg kg−1 for Pb and 0.0009 mg kg−1 for Cd. Soil properties were in the following range: pH 4.3–8 (Avg: 6.35), DOC 6.1–73 mg l−1 (Avg: 26 mg l−1), CEC 1.3–24 cmol kg−1 (Avg: 9 cmol kg−1) and SOC 0.5–5% (Avg: 1.7%). The concentration of water extractable fraction of trace elements was significantly correlated with pH (p <0.001), DOC (p <0.001 – p <0.05) and CEC (p <0.001) but their relationship with total content of trace element and SOC was rather weak, suggesting that total metal alone cannot be an indicator of toxicity or deficiency. Results show that pH, DOC and CEC are important soil quality parameters taking part in the solubility control of trace metals in the soil rather than their total concentration. The difference between land uses has been observed as well, suggesting that a change in land use can cause a change in trace element solubility.

Liming and fertilization impact on nutrient status in acid soil

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.

Mineral fertilization and liming impact on maize and wheat yield

The soil analyses for the field trials started in the spring of 2003 at site Donji Miholjac in eastern Croatia. Two different soil types were chosen with distance less then 1 km: silty loam dystric luvisol and silty loam calcaric regosol (limey substrate was excavated for the melioration canals and redeposited as top soil layer in 1986). The dystric luvisol was very acid (pHKCl 4, 02) with 1, 66 % humus, 149 mg kg-1 P2O5 and 167 mg kg-1 K2O. The calcaric regosol was slightly alkaline (pHKCl 7, 14) with lower content of humus (1, 42 %), phosphorus (139 mg kg-1) and potassium (109 mg kg-1). In the spring of 2003 the dystric luvisol was limed with 0, 10 or 20 t ha-1 carbocalk (total Ca content 344 g kg-1 and P 4, 6 g kg-1) on soil depth 30 cm. In the autumn of 2003 and 2004 the both soils (dystric luvisol and calcaric regosol) were fertilized first for maize and in second year for wheat with three different nutrient amounts: no fertilization, standard mineral fertilization and doubled phosphorus fertilization. Dystric luvisol pH reaction was influenced by liming and fertilization and changes are measured one year after liming (before maize sawing) and two year after liming (after wheat harvest): 10 t ha-1 carbocalk raised pH value for approximately 1 pH unit and 20 t ha-1 for 2 pH units. Influence of mineral fertilization on soil pH is evident especially on liming treatment with 20 t ha-1 carbocalk. Liming without fertilization resulted in increased pHKCl from 4.02 to 6.33 and 6.22 after first and second year, respectively. At the same time, liming with standard fertilization raised pHKCl up to 5.83 and 5.98, and with doubled phosphorus fertilization reached pHKCl was 5.72 after first year and 5.81 after second year. Liming did not affect maize yield but did slightly increased wheat grain yield and phosphorus removal by wheat grain. Mineral fertilization influenced significantly on yield and phosphorus and calcium removal comparing to production without fertilization. Although doubled phosphorus fertilization increased wheat yield and nutrient removal, only significant increasing comparing to lower phosphorus fertilization was phosphorus removal by wheat straw. Wheat and maize grains removed much more phosphorus and less calcium than straws.

Heavy Metal-Induced Oxidative Stress in Plants: Response of the Antioxidative System

Heavy metals (HMs) are among the most important environmental pollutants, particularly in areas with strong anthropogenic pressure. For plants, high levels of HMs are extremely toxic since they may act in several different modes: by the direct inhibition of plant growth and biosynthetic pathways or through the production of reactive oxygen species (ROS). Certain metals generate ROS due to their involvement in redox reactions like Fenton and/or Haber–Weiss reactions, while metals without redox capacity enhance ROS production by reducing the antioxidant glutathione pool, activating calcium-dependent systems and influencing iron-mediated processes. ROS production affects lipids, proteins, and DNA and consequently leads to cell death. In response, plants are equipped with complex enzymatic and nonenzymatic mechanisms involved in antioxidative defense to neutralize HM toxicity, and the main components of these mechanisms will be reviewed in this chapter.

Total and plant available micronutrients in acidic and calcareous soils in 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.

Reduced Dietary Selenium Impairs Vascular Function by Increasing Oxidative Stress in Sprague-Dawley Rat Aortas

This study aimed to determine whether low dietary Se content affects the function and mechanisms mediating the vascular relaxation of rat aortas, and to test the role of oxidative stress in observed differences. Male Sprague Dawley (SD) rats were maintained for 10 weeks on low Se (low-Se group; N = 20) or normal Se content (norm-Se group; N = 20) rat chow. Dose responses to acetylcholine (ACh; 10−9–10−5M) and the response to reduced pO2 were tested in noradrenaline-precontracted aortic rings in the absence/presence of the nitric oxide synthase (NOS) inhibitor nitro-l-arginine methyl ester (l-NAME), the cyclooxygenase 1 and 2 (COX-1, 2) inhibitor Indomethacin, and the antioxidative agent Tempol in tissue bath. mRNA expression of glutathione peroxidase 1 (GPx1), catalase (CAT), and Cu/Zn superoxide dismutase (SOD) was measured in rat aortas. Oxidative stress (Thiobarbituric Acid Reactive Substances; TBARS), antioxidative plasma capacity (ferric reducing ability of plasma assay; FRAP), and protein levels of GPx1 were measured in plasma and serum samples, respectively. Reduced ACh-induced relaxation (AChIR) (dominantly mediated by NO) in the low-Se group compared to the norm-Se group was restored by Tempol administration. Hypoxia-induced relaxation (HIR) (dominantly mediated by COX-1, 2), TBARS, and FRAP as well as GPx1 serum concentrations were similar between the groups. mRNA GPx1 expression in rat aortas was significantly decreased in the low-Se compared to the norm-Se group. These data suggest that low dietary Se content increases the local oxidative stress level, which subsequently affects the NO-mediated vascular response.

Phosphorus fertilization and liming impact on soil properties

Liming caused a significant changes in soil properties modifying soil acidity, nutrients and heavy metal availability. The paper is based on four-year filed trials conducted on two sites near Donji Miholjac in eastern Croatia: dystric luvisol and calcaric regosol. Conducted experiments confirmed that the lowest yield of all four crops was achieved on calcaric regosol. Liming dystric luvisol with 10 and 20 t ha-1 of carbocalk resulted in yield increasing. The highest influence of liming with 20 t ha-1 was on wheat yield increase, than on soybean and the lowest impact was on cabbage and maize yields. Ammonium-lactate soil P test and plant P removal data are sufficient for soil P balancing at low levels or no applied P fertilizer, but more fertilizer indicates that correction factor should be used for calculation impact of applied P fertilizer on increasing soil AL extractable P.