The effect of long-term mineral fertilization on the status of iron and heavy metals in soddy-podzolic soils

The long-term application of different mineral fertilizers in field experiments conducted at the Dolgoprudnaya and Luberetskaya agrochemical experimental stations and in the Chashnikovo Training and Experimental Soil-Ecological Center of Moscow State University resulted in an increase in the content of nonsilicate iron in soddy-podzolic soils of different texture, compared to the control (unfertilized) soils, which could be caused by an enhancement of the soil weathering. The greatest effect on the soil weathering was observed for nitrogen (ammonium nitrate) and potassium (potassium chloride) fertilizers. Periodic liming decreased the content of the nonsilicate iron minerals. The citrate-dithionite solution extracted 50 to 80% of the total zinc and 37 to 82% of the total strontium from the soil, which were probably bound to the nonsilicate iron compounds. The latter participate in the redistribution of the strontium arriving to the soil with phosphoric fertilizers: the content of the metal passed into the citrate-dithionite extract from the soil treated with simple superphosphate for a long time period and was 1.3 times higher than that extracted from the control soil.