Changes in the available phosphorus content of the agricultural soil of the Vojvodina Province, Serbia

The increasing phosphorus fertilizers use in agricultural production requires monitoring of the available phosphorus content in the soil. The AL available concentration of a soil is a key index that can be used to evaluate the P supply capacity of the soil and to estimate the optimal P fertilization rate. The aim of this paper was to examine the changes in the available phosphorus content in agricultural soil of Vojvodina Province, in the framework of soil quality monitoring. The examination included 1600 samples of agricultural soils from representative sites, properly distributed in a 4x4 km squares network. The available phosphorus content was determined by spectrophotometric method in AL extract (Egner and Riehm). The results of the research were compared with the results of the previous project in 1992, in order to detect the tendency of soil quality. The results indicated that soil class with the optimal content (15-25 mg/100 g) covered the largest area (21.4%), while the smallest area (5.4%), included soil with a toxic content (< 100 mg/100 g). The area of soil with very high to harmful content (50-100 mg/100 g) amounted to 5.8%. Compared to results from 1992, the amount of available phosphorus increased in all types of soil by 4.67 mg/100 g, except in the humofluvisol. The area of poorly supplied and soils with phosphorus content over 50 mg/100g has been increased. Research indicated inadequate application of fertilizers compared to the previous period