Vjekoslav Tadić

Evaluation of Different Soil Water Potential by Field Capacity Threshold in Combination with a Triggered Irrigation Module

Irrigation efficiency improvement requires optimization of its parameters like irrigation scheduling, threshold and amount of water usage. If these parameters are not satisfactorily optimized, negative consequences for the plantsoil system can occur with decreased yield and hence economic viability of the agricultural production. Numerical modelling represents an efficient, i.e. simple and fast method for optimizing and testing different irrigation scenarios. In this study HYDRUS-1D model assuming single- and dual- porosity systems was used to evaluate a triggered irrigation module for irrigation scheduling in maize/soybean cropping trials. Irrigation treatment consisted of two irrigation regimes (A2 = 60–100% field capacity (FC) and A3 = 80–100% FC) and control plot (A1) without irrigation. The model showed a very good fit to the measured data with satisfactory model efficiency values of 0.77, 0.69, and 0.93 (single-porosity model) and 0.84, 0.67, and 0.92 (dual-porosity model) for A1, A2, and A3 plots, respectively. The single-porosity model gave a slightly better fit in the irrigated plots while the dual-porosity model gave better performance in the control plot. This inconsistency between the two approaches is due to the manual irrigation triggering and uncertainty in field data timing collection. Using the triggered irrigation module provided more irrigation events during maize and soybean crop rotation and consequently increased cumulative amounts of irrigated water. However, that increase resulted in more water available in the root zone during high evapotranspiration period. The HYDRUS code can be used to optimize irrigation threshold values further by assuming different scenarios (e.g. different irrigation threshold or scheduling) or a different crop.

Jednodimenzijska difuzijska jednadžba za raspodjelu veličine čestica granulacije perlita za pročišćavanje

Preliminary communication Many filtration systems employing perlite granulations have been designed so far. Size distribution of perlite particles directly influences the retention properties of filter media. The information on the size distribution of perlite particles, used in each specific dead-end filtration process (the flow of fluid being filtered is perpendicular to the surface of filter medium), is crucial for the adequate design of filter medium. In order to facilitate the design of filter systems possessing filter media of this kind, a new and particular mathematical model has been developed for this present study. It is based on an appropriate partial differential equation and additional mathematical conditions, whose solution is an exponential function describing the probability density distribution of perlite particle sizes. The formulated model was experimentally verified by measuring the particle sizes of a perlite granulation using the morphometric method, based on the application of a standard light microscope and digital image analysis software. The fitting procedure of experimental data gave acceptable values of accuracy parameters high R-square factor (R = 0,905) and small value of the root-mean square error (MSE = 0,490).

IMPACT OF TECHNICAL SPRAYING FACTORS ON VERTICAL LIQUID DISTRIBUTION WITH AGROMEHANIKA AGP 440 AXIAL FAN SPRAYER

Original scientific paper The influence of technical spraying factors on vertical distribution of liquid and air velocity was observed and measured with vertical patternator device. In research, Lechler yellow (TR 8002C) and red (TR 8004C) nozzles are used with two different sets of fan rotor blades (two different air velocities) at 540 rpm of PTO. The research was set as controlled three factorial experiment (without the influence of weather factors) with 8 treatments in 4 repetitions, for each side of Agromehanika AGP 440 axial fan sprayer. Technical spraying factors (ISO nozzle number, settings of fan blades and spraying height) have a high significant impact (**) on the main properties of the research (vertical distribution of liquid and air velocity). By decreasing the ISO nozzle number and air velocity the increase of liquid deposit is found on vertical patternator and with the increase of measuring height a non-uniform distribution of liquid and air velocity is found. In addition, a non-uniform distribution of liquid and air velocity is established between the left and right sides of the machine. With regression analysis between the vertical distribution of liquid and air velocity on both sides of the machine, a statistically significant coherence is determined (left side of the machine: r = 0,96; p < 0,01; right side of the machine: r = 0,97; p < 0,01).

Damage of seminal maize hybrid in harvesting and husking

One of the biggest challenges for the safe maize production is the yield stability in a wide range of environments with different soil fertility, weather conditions, prevailing pests and diseases as well as cultural practices. In order to achieve it, new hybrids with higher tolerance to biotic and abiotic stress are continuously being created. In order to compare performance of maize hybrids in environments with different levels and types of stress, and relate it to the stalk lodging incidence, we compared performance of 64 maize hybrids obtained by crossing 16 inbred lines with four inbred testers in three different environments. Two environments at same location (Rugvica) differed in crop rotation, and the third environment at location Botinec was considered as dry because of low water capacity of the soil. Mixed models that included all design elements and genetic background of hybrids were used to analyze the effect of lodging on yield in different environments. The results show that stalk lodging had a significant effect on yield, but significant lodging x environment interaction indicates that this effect was rather environment specific.Sweet pepper Istra F1 hybrid was grown in a greenhouse on K rich soil. For evaluation of K antagonism, two K rates (55 and 85 kg ha-1) were applied in a randomized complete block design with four replications. Total number of fruits, total number of BER affected fruits as well as average fruit mass were recorded for each harvest. Fruit and leaf K and Ca content were determined at three plant growth stages (at the stage of the first, third and fifth fruit cluster). Higher K rate gave higher : average fruit mass (169.45 g), total number of fruits per plant (7.95), number of BER affected fruits per plant (3.82), K in leaves (5.44% DM), K in fruits (6.35% DM), but negatively correlated with Ca concentration in fruits (0.57% DM) and leaves (3.24% DM). This resulted in decreased marketable yield of sweet pepper fruits.