Effects of poly- and orthophosphates on the dynamics of manganese, zinc, and copper in plant and soil material of varied pH

A laboratory experiment was performed on light loamy sand to study the effect of potassium polyphosphate [(KPO3)n], potassium dihydrogen phosphate (KH2PO4) and triple superphosphate + potassium chloride (KCl) on the content and dynamics of soil manganese (Mn), zinc (Zn), and copper (Cu) determined using the methods of Rinkis (R) and Egner-Riehm-Domingo (AL) depending on the form and rate of PK fertilizers, different soil pH and Mn + Zn + Cu (M) supplementation. The results obtained by Rinkis's method were used to describe the dynamics of the three microelements. The average Mn, Zn, and Cu content in soil (determined in 1 mol dm(-3) HCl solution) was to a small extent related to the form and dose of PK fertilization. Increasing rates of CaCO3 caused an increase in the average Mn content in soil, an increase in Cu content only in soil of pH 7.49, but a decrease in Zn. The average Mn content in soil increased to day 40 of the experiment. The analyzed forms of Zn and Cu were retarded until day 20 of the experiment, after which they were activated in the course of time. The form of the fertilizer applied had a significant influence on the dynamics of Mn, a slight effect on the dynamics of Zn and, in general, had no influence on the dynamics of Cu. The most considerable retardation of Mn and Cu was observed in the objects fertilized with KH2PO4. The effect of increased (KPO3)n and KH2PO4 rates on the content of Mn, Zn, and Cu in soil was ambiguous and related to the soil pH and Mn + Zn + Cu supplementation. Soil higher doses of superphosphate + KCl resulted in a lower content of Mn(2+). It was only in soil of pH 7.08 that Mn + Zn + Cu supplementation caused an increase in the concentration of the analyzed forms of the microelements. In soil of other pH the effect of this supplementation was ambiguous. The correlation between soil pH and the soil content of the analyzed microelements was significantly positive for Mn, negative for Zn, and non-significant for Cu. In a vegetative trial, soil fertilization with KH2PO4 and (KPO3)n without M supplementation increased the average total biomass yield of barley, compared to the effect achieved by triple superphosphate + KCl fertilization. Soil liming depressed the average total yield of the crop. The M supplementation decreased the total greenmass of barley grown only on soil limed to pH 5.88 in all the fertilization objects. Compared to the objects with triple superphosphate + KCl, application of (KPO3)n and KH2PO4 decreased the content and uptake of Mn by barley in all the objects, those of Zn, only in non-limed soil, and had no effect on Cu. Liming decreased the content and uptake of Mn by barley more than the content and uptake of Zn. The Cu content and uptake by barley was related to the Mn + Zn + Cu supplementation rather that the PK fertilizer form or soil reaction. Correlation between the content of the microelements in soil and in plants in the analogous time of the study was negative for Mn, positive for Zn in the second and third cut, and for Cu in the first and second cut.