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Depending on their origin, sedimentary phosphate rocks (PRs) may differ in their P solubility, and, as a consequence, in their agronomic effectiveness. The effect of six phosphate rocks (PR) - originating from Algeria (ALG), North Florida (FLO), North Carolina (NCA), Senegal (SEN) Morocco (MOR) and Hyperphosphate (HYP) with various P solubility (evaluated by 2% formic acid, 2% citric acid, and neutral ammonium citrate) - as well as single superphosphate (SSP) and superphosphate + lime (SSP + Ca) (each P source on 4 P levels, with doses of 0, 100, 400 and 1600 mg P 2 O 5 ·kg -1 soil) on the shoot yield of tillering stage spring barley, soil available P (i.e. H 2 O, Olsen, Bray1, Lakanen-Erviö (LE) and ammonium lactate (AL) extractable P contents) were studied in pot experiments set up with acidic sandy soil (Nyírlugos, Hungary) and acidic clay loam soil (Ragály, Hungary), both with low P supplies.  The average spring barley shoot yield at the beginning of shooting was 95% higher on the colloid-rich acidic (pH KCl : 4.5) clay loam soil than on the colloid-poor acidic (pH KCl : 3.8) sandy soil. The differences in the solubility of phosphate rocks showed close correlation to the differences in P responses. On both soils, the correlation between total PR-P added and P responses in spring barley shoot yield was much weaker than that between neutral ammonium citrate soluble PR-P added and P responses in spring barley shoot yield. When phosphate rocks were applied as P sources, the comparison of soil test P methods showed a different picture on the two soils. In the case of the acidic sandy soil (Nyírlugos), the strongly acid LE-P (r² = 0.83) and AL-P (r² =0.74) tests gave the highest correlation coefficients with spring barley responses to P, while on the acidic clay loam soil (Ragály) these were achieved by the Olsen-P (r² = 0.88) and Bray1-P (r² =0.88) methods.

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The soil can act as a natural buffer by retaining toxic materials present in municipal and industrial wastes and sewage sludges. Countries of Eastern Europe currently have a limited industrial infrastructure for recycling wastes. One of the most rational and economic ways for these countries to dispose of their waste waters and sludges is to apply them to agricultural fields, thereby utilizing also their nutrient content. A U.S.-Hungarian research project was recently started with the aim of studying the fate and transport of selected heavy metals in the soil profile of cropped undisturbed soil monoliths. Preliminary experiments were carried out to study the adsorption-desorption processes of these chemicals on disturbed soil samples, and to investigate the plant-availability of different metal forms. Concentrations of Zn, Pb, Cr and Cd in the soil solution were found to decrease with increasing soil moisture content and length of the adsorption period, both showing hyperbolic relationships. Lower soil moisture contents increased both the solution concentrations and the adsorbed concentrations of the elements. Release of adsorbed Zn and Cd was higher than that of Pb and Cr. Higher plant-availability of inorganic forms of Ni correlated with a higher phytotoxicity as compared to Ni applied in sewage sludge.

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