Phosphorus is one of the major nutrients that influences plant growth but the amount ofbioavailable phosphorus in soil may have a negative effect on grassland production. A critical issue thataffects the phosphorus bioavailability is soil acidity. There are several strategies on how to managephosphorus availability on such soils. A number of studies have shown that high doses of phosphorusapplication can optimize plant performance, these doses have a long residual effect and cause increasedpH, CEC or organic content. However, application of phosphorus in small doses, can have long termbenefits from economic point of view. In this paper we propose to study the dynamics of phosphorus on apajiste an acid soil (aluviosol) at pH = 5.3. This meadow is situated in the village Borlova, Caras-Severin, at the foot of Mount Mic Were applied fertilizer nitrogen and phosphorus in 4 variants and 4repetitions arranged in randomized blocks, as follows: N0P0, N1P0, N0P1 and N1P1, where N0P0unfertilized control, N1 = 150 kg N/ha was applied split (100 kg/ha before the vegetation and 50 kgN/haafter the first stitch) and P1 = 50 kg P2O5/ha. P was applied once before the vegetation. Soil sampleswere taken at 0-10 cm depth, dried in air, grounded and sieved trough 2 mm sieve. Total phosphoruscontent in soils was determined by extraction in aqua regia and available phosphorus content by Egner -Rhiem – Domingo method. Reading of total phosphorus and available phosphorus concentrationfrom soilsamples was done with Cintra 101 spectrophotometer After analysis it was found that although totalphosphorus content in the soil is high available phosphorus content is relatively low. Maximum plantavailable P occurs at approximately pH 7. As pH changes in either direction, P availability is decreased.Although P levels increase with P fertilizer applications, the available content is low, so it is crucial thatP fertilizer be applied annually at reasonable rates to satisfy plant needs.

acid soil, phosphorus, grassland, fertilization

Presentation: oral