Effect of increasing fertilizer doses on the soluble P, Cd, Pb, and Cr content of soils

Recently we are witnessing a tremendous pollution of air, water and soil. The environmental pollution is primarily caused by the rapidly increasing industrial production, deposition from gases emitted by road and aerial traffic, utilization of municipal sewage-water and -sludge and other urban and industrial wastes. As for agriculture, fertilization also has an un-desirable impact on the environment. With the application of phosphorus (P) fertilizers, their heavy metal contaminants, e.g. the very harmful cadmium, may accumulate in the soil. In the National Long-Term Field Fertilization Trials in Hungary, the effect of increasing fertilizer applications was studied on the plant available, ammonium lactate (AL)-soluble P and ethylene diamine tetraacetic acid (EDTA)-soluble cadmium (Cd), lead (Pb) and chromium (Cr) concentration in the upper 20 cm soil layer of three experimental sites. The experiments were set up with two different four-year crop rotations of winter wheat (Triticum aestivum L.), maize, maize (Zea mays L.) and pea (Pisum sativum L.); winter wheat, maize, maize, winter wheat in nine sites and with a maize monoculture in four sites in 1967-69. The discussed results relate to soil samples taken in the last year of the 7th rotation, i.e. they reflect the long-term effect of 28 years' fertilization. Four out of the 40 NPK fertilization treatments were chosen for the present study. There could be detected a marked increase in the available P content in the experimental soils as a result of long-term fertilization. As compared to the unfertilized control plots, the increase in P content was 2.5-4.6-fold at the different sites. The environmental impact of Cd, Pb and Cr at the investigated experimental sites was not considerable. Slight concentration increases were detected only for Pb, and the highest Pb contents were measured in the site of heaviest traffic.