Domagoj Rastija

Response of maize to fertilization with KCl on gleysol of Sava valley area

Five maize ( Zea mays L.) 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 2 O/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 2 O/ha every third year and a choice of tolerant hybrids.

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.

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.

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.

Four‐Year Dynamic of Potassium on Two Sites Interpreted by Different Soil Tests

Three soil–potassium (K) tests were compared using soil and plant samples collected during fertilization and liming experiments in Croatia on very acid dystric luvisol and slightly alkaline calcaric regosol. Soil samples were analyzed for pHKCl, pHH2O, organic matter, and ammonium lactate (AL, pH 3.75)–extracted phosphorus (P) and K. In addition, K was extracted with ammonium acetate (AA, pH 7) and with ammonium acetate ethylenediaminetetraacetic acid (AAEDTA, pH 4.6). In spring 2003, the dystric luvisol was limed with 0, 10, or 20 t ha‐1 carbocalk (by‐product at sugar beet processing, effective neutralizing value 69.1%). During the next four seasons, four different crops were grown without fertilization, with standard fertilization, and with doubled P amounts. All three soil K tests showed highly significant correlations of fertilization impact on extractable soil K and can be efficiently used for fertilizer recommendations. Balance calculation is closer to results of extractable K on fertilized plots than on control plots and use of AAEDTA or AL than AA extraction.

LIMING AND FERTILIZATION IMPACT ON NUTRIENT REMOVAL BY MAIZE AND WINTER WHEAT

Heavy application of mineral fertilizers, base cations leaching and removal with harvested crops lead to soils acidification what could be a limiting factor of the field crops yield. The aim of this study was to provide data for sustainable cropping by evaluating the impacts of liming and fertilization on maize and wheat yield and calcium, potassium and magnesium concentration in plant tissue and removal by above ground mass. The field trials were conducted during two years in a randomized block design in three replicate on two sites in the eastern Croatia. Mineral fertilization had stronger impact on maize and wheat yield than liming. Liming increased calcium concentration in grain and above ground mass, while potassium concentration was influenced by mineral fertilization. Overall, the higher concentrations of base cations were found in vegetative mass of the both crops, with exception of magnesium whose concentration was higher in the wheat grain. Concerning particular nutrient removal significant differences were found, as well as among treatments. Generally, mineral fertilization or its combinations with liming influenced more on the nutrients removal, than liming apart.

Comparison of Chemical Extraction Methods for Determination of Soil Potassium in Different Soil Types

Determining potassium supply of soil plays an important role in intensive crop production, since it is the basis for balancing nutrients and issuing fertilizer recommendations for achieving high and stable yields within economic feasibility. The aim of this study was to compare the different extraction methods of soil potassium from arable horizon of different types of soils with ammonium lactate method (KAL), which is frequently used as analytical method for determining the accessibility of nutrients and it is a common method used for issuing fertilizer recommendations in many Europe countries. In addition to the ammonium lactate method (KAL, pH 3.75), potassium was extracted with ammonium acetate (KAA, pH 7), ammonium acetate ethylenediaminetetraacetic acid (KAAEDTA, pH 4.6), Bray (KBRAY, pH 2.6) and with barium chloride (

SIMPLE REGRESSION MODELS FOR PREDICTING SOIL HYDROLYTIC ACIDITY

K_{BaCl_2 }