Ivica Kisić

Heavy Metals Uptake by Aerial Biomass and Grain of Soybean

All phases of crude oil exploitation, starting from drilling works to the construction of underground pipeline networks, including transport, processing and storage, are causing interventions and procedures hazardous to the environment. Although modern technical solutions and materials are used in all segments of petroleum industry warrant a high degree of safety, the occurrence of various incidents is unfortunately not fully excluded. Incidents leading to pipeline spillage and crude oil contamination of the environment constitute a hazard to natural resources, primarily soil and water, and depending on their severity can jeopardize, for a shorter or longer time, the intended use of land on which the incident occurred, namely make it unsuitable for plant production. Petroleum and gas fields are located in Pannonian area where cultivation of agricultural crops is dominated and among them the most represented are corn, wheat and soybean. On the other side, these (petroleum and gas) activities generate waste - drilling fluids which contain different chemical compounds, some of which are ecologically hazardous (hydrocarbons), or toxic substances (heavy metals). As already mentioned, drilling fluids contain increased levels of some heavy metals (barium, zinc and mercury), so their possible application as liming material involves the risk of heavy metal accumulation in soil and plants (Agbogidi et al., 2007). To assess the extent to which such material may be useful or harmful to soil, and thereby to plants grown on it, since pollutants enter the animal and human food chain via soil and plants, investigations into this problem were undertaken (Nelson et al., 1984 ; Lengrand et al., 2005 ; Kabata-Pendias & Mukherjee, 2007). In soybean and wheat grain more nickel and copper were determined compared to soybean and wheat biomass. Also, higher content of zinc in wheat grain compared to biomass was determined. In all other cases, higher concentrations of heavy metals in aerial biomass than in grain of investigated crops were determined. Regarding other investigated crops soybean had the highest enrichment coefficient for cadmium, copper, nickel and zinc.

Yields and yield components of maize (Zea mays L.) and soybean (Glycine max L.) as affected by different tillage methods

Abstract At the experiment station of the Krizevci College of Agriculture, yield and yield components of maize (Zea mays L.) and soybean (Glycine max) grown in rotation under five different methods of tillage were investigated. The aim of this study was to determine the effect of different tillage methods on yield and yield components of maize and soybean. The results and the determined number of plants per hectare of maize and soybean show that more favorable conditions for germination are in variants where ploughing performed in the autumn (variants C, D and E). During a four-year study, the minimum number of plants per hectare of maize and soybean was found in variant A. The dry season in panicle stage of maize in 2006 has lowered yields compared to 2008, and the drought in 2007 during the seed-filling period reduced the yield and the 1000 kernel weight of soybean compared with 2009 in all variants of tillage methods. The highest grain yield of maize was recorded in variant B. During 2006, with the unfavorable weather conditions, the lowest grain yield of maize was recorded in variant E with intensive tillage treatment. The highest yield of soybean was recorded in variant E, but there were no statistically significant differences compared to variants with the reduction of additional tillage interventions (variant B, C and D). With respect to maize grain and soybean seed yield, variant A was the lowest. Considering the achieved yields of maize grain, there is a possibility of reducing additional tillage interventions, whilst for achieving higher yield of soybean seed intensive tillage is recommended.

Yields and yield components of maize and soybean as affected by different tillage methods

Abstract At the experiment station of the Krizevci College of Agriculture, yield and yield components of maize (Zea mays L.) and soybean (Glycine max) grown in rotation under five different methods of tillage were investigated. The aim of this study was to determine the effect of different tillage methods on yield and yield components of maize and soybean. The results and the determined number of plants per hectare of maize and soybean show that more favorable conditions for germination are in variants where ploughing performed in the autumn (variants C, D and E). During a four-year study, the minimum number of plants per hectare of maize and soybean was found in variant A. The dry season in panicle stage of maize in 2006 has lowered yields compared to 2008, and the drought in 2007 during the seed-filling period reduced the yield and the 1000 kernel weight of soybean compared with 2009 in all variants of tillage methods. The highest grain yield of maize was recorded in variant B. During 2006, with the unfavorable weather conditions, the lowest grain yield of maize was recorded in variant E with intensive tillage treatment. The highest yield of soybean was recorded in variant E, but there were no statistically significant differences compared to variants with the reduction of additional tillage interventions (variant B, C and D). With respect to maize grain and soybean seed yield, variant A was the lowest. Considering the achieved yields of maize grain, there is a possibility of reducing additional tillage interventions, whilst for achieving higher yield of soybean seed intensive tillage is recommended.

Precise Soil Sampling Method for Agricultural and Environmental Research Based on New Circular Soil Probe Apparatus

Conventional soil sampling usually implemented in Croatia considers sample weight of 2 kg per 4-5 ha area, which means that representative sample in relation to soil mass up to 30 cm depth is presented through the ratio 1:10000000. New sampling method changes the ratio to 1:625000, thus increasing amount of sampled soil 16 times with assumption that such sample better describes investigated area. Moreover, new soil sampling probe can be used for precision farming purposes where the central point of the probe ring is positioned with precision of ±1 cm and represented with 4, 8 or 16 samples taken in 50 cm radius from the center. Soil probe prototype was tested on agricultural land of 4 ha area with total number of 200 samples. To justify application of new constructed probe, this study gives results of geostatistical analysis of spatial variability in soil pH values up to 30 cm depth. Ordinary kriging was used as interpolation method. Spatial structure of soil parameter was analyzed by calculating semivariograms and approximated by exponential model. Root-mean-square error (RMSE) of prediction was used as measure for the best model evaluation. Interpolation analysis of reduced number of samples per investigated area of 4 ha resulted in deviation in RMSE of 13,2 % when 50 % less samples were randomly introduced, and 41 % with 60 samples, compared to total of 200 samples. Using new soil sampling method for soil survey and applied geostatistical tools provides a solution for quantifying spatial variability of soil properties, possibilities for commercial activities and a way to introduce variable rate technology in agricultural input application which can optimize farm profitability through improving yield, reducing input costs and minimizing input losses to the environment.