Lajos Szabó

Uptake of Microelements by Crops Grown on Heavy Metal–Amended Soil

Abstract A small‐plot field experiment on microelement pollution (Aluminum (Al), Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Mercury (Hg), Lead (Pb), Zinc (Zn)) was initiated in 1994 at Tass‐puszta Model Farm of Gyöngyös College, Hungary. The experimental plants were winter wheat (Triticum aestivum L. emend. Fiori et Pool.) in 1995, maize (Zea mays L.) in 1996, and sunflower (Helianthus annuus L.) in 1997. Plant samples were taken each year during the vegetation period at phenophases characterized by intensive nutrient uptake. The Al content of crops was not influenced by Al load of the soil. Arsenic accumulation was not considerable in the grain with the highest As load. Cadmium accumulation was significant both in vegetative and reproductive parts of crops with increasing Cd loads of the soil. The Cd content was about 10–40 times higher in treated sunflower seeds than in the control; as a result the seeds were not suitable for consumption. Cadmium can accumulate in the reproductive tissue, so it is a real risk in the food chain. In the first year, Cr(VI) had a toxic effect on wheat, but it was not mobile in the soil–plant system. Vegetative parts of winter wheat accumulated significant amounts of Hg, but maize and sunflower seeds did not accumulate Hg. Lead, Cu, and Zn showed only moderate enrichment in crops following increasing loads in the soil.

Changes of availability of some microelements in heavy metal amended soil

Introduction Environmental pollution is placing and ever-increasing load on various environmental resources, including soil. There are increasing interest in potentially toxic microelements and hazards related to heavy metals and environmental pollution (Szab6-Fodor 1998, Fodor 2000). The loading threshold values for soils is a function of the soil properties (pH, soil organic matter content, clay content, type of clay materials, etc.) (Kaddr-Morvai 1998, Fodor 2002). There are no universal solvents or methods that provide a satisfactory characterization of the exchangeable or plant available fractions of all harmful materials in various soil types. At the present time, the total content is used to estimate the level of microelement contamination (Fodor-Szabo 2003). As most microelements and heavy metals are strongly bonded to soil particles (minerals and oxides), the total content does not indicate the actual availability and/or mobility of elements. From physiological, ecological and hazard aspect, the more soluble fractions are more important (Fodor 1998, Fodor-Szabo 2003, Kadar et al. 2000). Our objective was to follow the changes of mobility of various microelements after heavy application rates to the soil.

Chemical Detection of Heavy Metals Applied at High Rates to Soil

Abstract The detection of eight micropollutants was studied in a field trial. Al, As, Cd, Cr, Cu, Hg, Pb, and Zn soluble salts were applied at rates of 30, 90, and 270 kg ha−1. The total element content was measured using HNO3+H2O2, and the exchangeable/soluble content was measured with NH4‐acetate+EDTA extraction. After 1 year, nearly all of the applied Cu, Pb, Cd, Zn, and As could still be detected in the plow layer in an exchangeable form, but the Cr and Hg were not detectable. Two years later, approximately two‐thirds of the added Cd and only about one‐third of the applied Cu, Pb, Zn, and As were found in exchangeable forms, whereas Cr and Hg were only marginally detected. With time, fixation of these elements in less exchangeable forms occurred. Cadmium remained exchangeable for a longer time than the other elements and could be measured by both analytical methods.

Soil management and crop biomass removal impacts on soil organic matter content

A well-recognized soil quality indicator is soil organic matter (SOM) content (SOMC), a soil component upon which agroecosystems and agricultural production are dependent. Agricultural practices greatly influence SOMC (Larson and Pierce, 1994) and SOMC affects crop production (Guernsey et al., 1969). Research has shown positive relationships between increased SOMC and appropriate management practices with organic carbon added to the soil (Peterson et al., 1998; Robinson et al., 1996). Removing residues increases soil erosion losses (Gupta et al., 1979), and residue harvest removes with it plant nutrients that must be replaced with fertilizer (Rasmussen and Rode, 1988) or manure applications (Sommerfeldt et al., 1988). Even with these negative impacts, it seems residues, or part of the residues, can be removed from selected soils without decreasing soil quality if appropriate management practices are used, i.e., reduced tillage, manure application, and crop rotations (Havlin et al., 1990). These practices are known to attenuate the effect of residue removal. Stevenson (1965) reported that rotations including legumes maintained a higher SOM level than continuous cropping with no leguminous crops. Few studies have explicitly measured the effect of com (Zea mays L.) residue removal on soil organic carbon (SOC; SOC = 1.6 x SOM). Karlen et al. (1994) found that normal and doubled residue addition treatments resulted in higher SOMC than the residue removal treatment within no-till continuous com in Iowa. Changes in SOMC occur slowly over periods of decades so long-term experiments are necessary to measure these changes. However, no SOMC analysis of long-term experiments designed to evaluate the effects of residue removal on SOMC when using a variety of crop and soil management practices has been located. Understanding the net effect of management alternatives on SOMC with residue removal, and the soils for which they will best work, requires research. The objective of this study is to evaluate impacts of manure and mineral fertilization application and crop rotations on soil carbon change when crop biomass is incorporated vs. when it is removed.