Jasna Šoštarić

Wheat and maize yield variations in the Brod-Posavina area

In general, wheat and maize yields in the Brod-Posavina County (BPC) were about 15% lower (10-year means 1981–1990) in comparison with their yields in the region. Wheat yield variations in the region among the years were higher in comparison with maize yield. For example, the highest yield of wheat and maize were higher than the lowest yield for 61% and 34%, respectively. Analogic comparison for Slav. Brod and N. Gradiska municipalities were 78% and 41% (wheat), as well as 41% and 24% (maize), respectively. In the last 8-year period, mean wheat yields in the region were for 17% lower and maize yield for 4% higher in comparison with mean yields of 80ies. These differences in level of BPC were 10% lower and 12% higher, for wheat and maize, respectively. We presume that low or absence effects of tile drainage because of their inadequate servicing could be expalantion for wheat yield decreasing. The lower yields of wheat are mainly in connection with oversupplies of water. However, low maize yields are in connection with water shortage and the higher air-temperatures. Low supplies of P and K are additional factors of low yields of field crops in the hydromorhic soils of the BPC.

RESPONSE OF MAIZE AND SOYBEANS TO FERTILIZATION WITH PHOSPHORUS AND POTASSIUM ON ACID SOIL

The field experiment of P and K fertilization was conducted in spring of 2004 (a = ordinary fertilization, b = a + P1, c = a + P2, d = a + P3 , e = a + P1, f = a + P2, g = a + P3 , h = a + P2K2. The amounts of added either/or phosphorus (P2O5) and potassium (K2O) were (kg ha-1) 500, 1000 and 1500, for the step 1, 2 and 3, respectively. The triplephoshate enriched with sulphur and zinc (45% P2O5 + 1. 2% S + 0.06% Zn) was used for P fertilization. Potassium salt (KCl containing 60% K2O) was source of K. Nitrogen amount was equilized for all treatments by adequate quatities of CAN (calcium ammonium nitrate: 27% N). The experiment was conducted in four replicates for crop rotation maize (2004) and soybean (2005: residual effects of the fertilization). Applied fertilization considerable influenced on increases of plant available P and K in soil, while differences of pH and humus among tretaments were in range of statistical error. Also, both P and K single fertilization gave tendency to decrease hydrolitical acidity. In general, grain yields of maize were high and ameliorative fertilization had moderate effects on maize yield as well as P and K in grain and leaves increases. Only applications of the highest K rate and PK combination resulted by significant yield increases, for 5% and 12%, respectively. Only application both P and K nutrients resulted by increase of grain quality (protein content). Residual influences of the fertilization were higher because soybean yields were increased up to 21% (influences of P), 17% (influences of K) and 30% (PK influences). However, protein and oil contents in grain were indenpendent on fertilization.

Influences of irrigation and fertilization on soybean properties and nitrogen leaching

Influences of irrigation rates and N fertilization on soybean grain yield and N leaching were tested under field conditions on Osijek, during the growing seasons 2001, 2003 and 2005 (A). The irrigation started on level of 80% field water capacity, A1 (FWC) and at level of 65% FWC, A2 and irrigate up to FWC, and non-irrigated, A3. Increased rates of N: 0, B1; 100, B2 and 200 kg N ha −1 , B3 were applied. The experiment was conducted by split-plot method. Ebermeier’s lysimeters (open type: 80 × 80 × 10 cm) were conducted for collecting leachate for measuring nitrogen leaching. The soybean grain yield showed statistical very significant differences in growing season, irrigation and interaction of growing season and irrigation. Mean leaching NO 3 -N varied from 0.32 kg N ha −1 to 7.88 kg N ha −1 in year 2001, while were greater in year 2005 and varied form 2.41 kg N ha −1 to 23.71 kg N ha −1 .

Influences of irrigation and N fertilization on maize ( Zea mays L. ) properties

Water quantity and the application period are highly significant for achieving high yield. Also, the best results can be obtained with the proper amount of macro and micro nutrients, especially nitrogen. However, nitrogen is ecologically a very sensitive element. The climatic factors and irrigation have a great effect on the efficiency of fertilization. Therefore, the objective of this study was to examine the effects of supplemental irrigation and nitrogen fertilization on grain maize yield and yield components. The maize grain yield and yield components showed statistical differences between the 2000 growing season (10.64 t ha-1) and 2002 (12.14 t ha-1). Irrigation variant A1 (keeping soil water from 80 to 100% FWC) gave the best results in yield and in all the researched components. Medium (B2) and higher nitrogen level (B3) also gave the best results in the research except grain/ear ratio which had the best results with B1 (100 kg N ha-1). The highest level of irrigation (80-100% FWC) and nitrogen level (200 kg N ha-1) did not give statistically significant higher yield and yield components. Applying 150 kg N ha-1 in the year 2000 also proved environmentally suitable quantity of nitrogen on the researched soil since the higher level of N (B3) did not increase the yield.

Responses of grain composition traits to high plant density in irrigated maize hybrids

The objective of this study was to examine the effects of supplemental irrigation and higher plant density on grain composition traits of ten maize hybrids. The experiment was grown in Osijek (Eastern Croatia) in 2002, 2003, 2004 on eutric cambisol, and consisted of factorial combination of two irrigation levels (non-irrigated and irrigated), two plant densities (standard – 57140 and high – 63492 plants ha-1, respectively), and ten commercial maize hybrids of FAO maturity groups 500-700. A self-moving sprinkler was used for irrigation to maintain water content in soil from 60% to 100% of field water capacity. Irrigation consistently affected grain yield across the years, but not the composition traits. Higher density did not affect grain traits except for water content, protein and oil concentration in 2002. Averaged across ten hybrids and two irrigations levels in 2002, higher density decreased protein concentration from 8.92% to 8.76%, and oil concentration from 3.71% to 3.65%.

Soil tillage impacts on nutritional status of wheat

Soybean were grown under field conditions on chernozem soil for four growing seasons (from 2002 to 2005). Three treatment of soil tillage were applied as follows: a) conventional tillage, b) reduced tillage (diskharrowing instead of ploughing) and c) no-till (zero-tillage). In general, the characteristics of growing season (the factor „year“) were more influencing factor of soybean nutritional status (aerial part in stage of full-developed pods) in comparison with the soil tillage. In our study, low influences of applied soil tillage treatments on nutritional status of soybean were found because significant differences on soybean composition were found only for four (Cu, Cr, Sr and Ba) from total 20 analysed elements. For example, conventional tillage resulted by the higher plant Cu (by 15% and 18% in comparison with DH and NT, respectively), and the lower plant Sr (by 12% and 16%, respectively) and Ba (by 26% and 23%, respectively), while under DH conditions by 22% lower plant Cr was found. Main nutrient...

Response of Maize (Zea mays L.) Grain Yield and Yield Components to Irrigation and Nitrogen Fertilization

Grain yield of maize is mostly affected by amount of available water and nitrogen and correlated to yield components. In this 2-years study the influence of different irrigation water amounts (a1=rainfed; a2=60-100% field water capacity (FWC); a3=80-100% FWC), nitrogen fertilizer levels (b1=0 kg*N*ha-1; b2=100 kg*N*ha-1; b3=200 kg*N*ha-1) and hybrids (c1=OSSK515; c2=OS5997; c3=OS5775; c4=OS5885) on grain yield and yield components was tested. Furthermore the correlation analysis as well as direct and indirect path coefficients were used to analyse the connection between yield and yield components (grain number/cob, grain weight, 1000 grain weight, cob length, cob weight) across tested treatments. The influence of all tested factors was significant (P<0.05) in both years of study. Specific study results were obtained in extremely wet year 2010 when irrigation water reduced grain yield and yield components (a1=9.9; a2=8.8; a3=7.8 t*ha-1). Opposite to year 2013 when irrigation water increased grain yield as well as yield components (a1=8.9; a2=9.7; a3=10.3 t*ha-1). Nitrogen fertilizer was significant to all tested variables in both years of the study (b1=5.7; b2=9.2; b3=11.7 t*ha-1 in 2010 and b1=6.3; b2=8.9; b3=10.6 t*ha-1 in 2013). Generally, the greatest amount of nitrogen fertilizer the larger yield or yield components are achieved. The influence of hybrid was significant for all tested variables with exemption to 1000 grain weight and grain weight/cob during growing season 2013. In both years of the study hybrid c2 OS5997 achieved the highest yield as well as yield components. Correlation analysis showed strong positive correlation between yield and cob weight (r=0.77 (2010); r=0.84 (2013)) what is confirmed with direct and indirect path analysis test.

Phosphorus fertilization impacts on soil nutritional status

Ameliorative fertilization with P fertilizer resulted by positive (increases of mobile fraction of P up to more than 4-fold, and AL-soluble P up to 6-fold) and negative (hydrolitical acidity increases up to 2.05 cmol kg−1) effects in soil. It is important that mobile fraction of harmful elements, especially Cd, were in all applied treatment in level of the control. For alleviation of negative effects we recommend combination ameliorative fertilization with liming.