S olubility and availability metals in soil are directly related with soil pH, Fe and Mn oxidesand NOM. Man y scientific studies have generated a large body of information on benefits and environmental impacts associated with land application of mineral fertilizers. For improving soil fertility, in Romania is widely used mineral fertilization (NPK). Due to its influence on soil chemical properties, especially soil reaction which represents the pre eminent factor controlling the chemical behavior of metals and other important processes in soil, the aim of this paper is to establish some relation between these factors. Field trials with the following fertilization variants: N 0 P 0 K 0 , N 100 P 0 K 0 , N 200 P 0 K 0 , N 100 P 50 K 50 , N 200 P 50 K 50 , N 100 P 100 K 100 , N 200 P 100 K 100 , N 100 P 150 K 150 , N 200 P 150 K 150 were placed in S.D. Timisoara, on a cambic chernozem soil. Soil type is cambic chernozem with following features: total density ranged between 2.43 g|cmc and 2.58 g|cmc, lower and higher;total porosity has medium values, excepting the soil surface were total porosity has highest value: 47%; soil reaction is weakly acid, pH=6.18; humus content of soil is ranged between 3.28 si 2.10%, nitroge content is ranged between 3.08 la 2.04; phosphorus soil content is low – 13.0 ppm, and potassium content of soil is medium– 184 ppm;the value of cationic exchange capacity of soil is 30.35 me/100g. S oil samples, in three replicates for each variant were analyzed in order to determine soil pH by potentiometric method (water extraction, 1:2.5 ratio) and available metals content ( Acetate - EDTA mixture extraction followed by FAAS determination). The results suggested that is a very close dependence between the level of mineral fertilization applied and soil metal availability. The increase of nitrogen doses usually leads to available metal content increasing, due to pH decrease. On the other side P and K fertilization limit the action of nitrogen fertilization on pH, but at high doses, the available metals content decrease, because of low solubility phosphate-metal compounds formed in these conditions. It is very important to know the limits, in order to avoid soil properties depletion, deficiency or excess, soil pollution and, not at least yield quality diminishing.

mineral fertilization, soil reaction, metal availability.

Presentation: oral