Over-fertilization before 1989 resulted in high phosphorus levels in agricultural soils of Hungary, but the accumulated reserves seem to have been depleted in recent decades due to under-fertilization. The aims of this study were to map the spatial pattern of phosphorus level and its change in the last few decades in Hungary to document the effect of fertilization and underlying socio-economic conditions on P concentrations, to identify the role of soil properties in changing soil soluble P and to quantify the total amount of soluble phosphorus level change in agricultural areas in the last few decades in the country. Two soil datasets were analyzed (National Pedological and Crop Production Database of Hungary and the Land Use/Land Cover Area Frame Survey, LUCAS, topsoil dataset), representing the status of soil nutrient contents in 1989 and in 2009. The measured phosphorus concentrations were compared to the reported phosphorus fertilization inputs. We also evaluated the effect of some important soil properties on soluble phosphorus content and on its change. We produced three maps by using kriging methods: soluble phosphorus levels in 1989, in 2009 and the change between 1989 and 2009. The results confirmed that phosphorus levels in agricultural areas depend mainly on agricultural use, while soil physical characteristics play a smaller role. Nevertheless, we demonstrated that the decrease in soil phosphorus levels was significantly influenced by soil chemistry (pH and CaCO3
content). The mean soluble phosphorus level was 108 mg/kg in 1989 and 28 mg/kg in 2009, and the median values were 100 and 22. The total loss (caused by harvesting, fixation and erosion) is ~1.5 million tons of soluble phosphorus, which is twice as much as the reported phosphorus balances indicated. In conclusion, our results show that approximately 50% of agricultural areas in Hungary are characterized by a very low supply of phosphorus (according to the latest data), posing a risk of nutrient depletion in these areas.
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