Igor Kovačev

Effects of tillage systems on soil water content and yield in maize and winter wheat production

The four-year trial was conducted in north-western Slavonia (main arable crop producing region in Croatia) to evaluate the effects of different tillage systems on the water content of silty loam soil (Albic Luvisol) and yields of maize (Zea mays L.) and winter wheat (Triticum aestivum L.). The tillage systems compared were: conventional tillage; reduced conventional tillage; conservation tillage I; conservation tillage II (CM); no-tillage (NT). During the study period, there were one dry, two wet and one average season. Soil water content (SWC) was measured at 0–5, 15–20 and 30–35 cm depths on a monthly basis. Tillage systems had significant ( P < 0.05) effects on SWC and yields. The highest average SWC in all seasons was measured under the NT system, followed by the CM system. In the second season, the highest yield was measured under the NT system while in all other seasons, it was under the CM system.

Effects of tractor bias-ply tyre inflation pressure on stress distribution in silty loam soil

The aim of this paper was to quantify vertical stress distribution in silty loam soil by applying three combinations of tyre inflation pressures of front and rear wheels of a four-wheel drive tractor weighing 3560 kg. The tyres on the tractor were bias-ply, front 11.2-24 and rear 16.9-30, and inflation pressures were 67, 100, and 150% of the recommended pressure. Soil stresses were measured at 10, 30, and 50 cm depths using a stress transducer consisting of ten sensors with a 10 cm distance between sensor centres. Decrease in tyre inflation pressure resulted in a decrease of maximum soil stress at all measured depths. Tyre inflation pressures greatly influenced soil stresses measured in the topsoil. Maximum soil stress in the topsoil depth below front wheel tyres was significantly higher than that below rear wheel tyres. There were no significant differences between tyre contact areas at recommended, high, and low tyre inflation pressures.

Mechanical properties of ten-egg boxes made of different materials

This study was conducted to evaluate mechanical properties of ten-egg boxes, which are the most commonly used egg boxes in many countries of Central and South-Eastern Europe. Six ten-egg boxes were tested, two made of cardboard, two made of expanded polystyrene and two made of general purpose solid polystyrene, each from a different producer. There were no significant differences in basic dimensions between tested boxes of various materials, while the significant differences were occurred in weight and box wall thickness. Test included measuring of vertical forces required for deforming complete box and at particular place for each egg in a box till contact with eggs. According to the obtained results, cardboard boxes can provide the best mechanical protection for eggs. The average force required for deforming complete cardboard box was 83.6% higher than for solid polystyrene box, and even 289.5% higher than for expanded polystyrene box. The average force required for deforming cardboard box at particular place for each egg in a box was 60.8% higher than for polystyrene box, and 74.0% higher than for expanded polystyrene box. The disadvantage of cardboard boxes is that they are not resistant to the impact of moisture as polystyrene boxes and in the case of an increase in box moisture due to storage in inappropriate conditions their mechanical resistance decreases.

Some Physical, Morphological and Mechanical Characteristics of Turkey (Meleagris gallopavo) Eggs

The physical, morphological, and mechanical characteristics of eggs play an important role in the processes of embryo development and hatching. Some physical, morphological, and mechanical characteristics of turkey (Meleagris gallopavo; Zagorje breed) eggs collected during two laying cycles from same turkey hens were determined in this study. The average values of length, width, geometric mean diameter, weight, surface area, volume, sphericity, eggshell thickness, and eggshell density were determined as 66.61 mm, 46.84 mm, 52.66 mm, 77.74 g, 8712.42 mm2, 76553.49 mm3, 79.31%, 0.354 mm and 3.13 g cm-3, respectively. Eggs collected during second laying cycle were, on average, larger and heavier in comparison with those collected during first cycle. Average albumen, yolk and eggshell percentages of the eggs collected during two laying cycles were 58.11%, 29.50% and 12.39%, respectively. The highest breaking strength was obtained when the eggs were loaded along the X-front axis and the least breaking strength was required along the Z-axis. The average breaking strength, absorbed energy and firmness in loading along the X-front axis were found to be 73.80 N, 9.75 N mm and 280.30 N mm-1, respectively.