An impact of municipal sewage sludge and wheaten straw on some indicators of soil fertility

In a two-factor pot experiment the impact of applied diverse doses of municipal sewage sludge and equal dose of wheaten straw, with and without supplemental mineral N and NPK fertilization, on some fertility properties of soil was assessed. The soil used in the experiment was acid brown incomplete soil (good rye complex). The grass — Festulolium — was the test plant, harvested four times and in the second year — common sunflower and blue phacelia. After the harvest of phacelia, the pH (in 1 M KCl), the content of total nitrogen, total carbon and the available forms of P, K and Mg were analyzed.

Fertilization with sewage sludge and straw failed to have a significant influence on the change of the soil pH. However, all doses of sewage sludge + straw, in comparison with the control, significantly increased the content of total carbon (from 31.8 to 37.8%) and total nitrogen (from 34.3 to 52.2%) in the soil. There was significantly more phosphorus available in the soil from all the objects with sewage sludge and straw than in the soil from the control object (from 8.2 to 21.6%), while the content of potassium was higher only in the soil from the object with 1.5% of sewage sludge + straw and magnesium at the highest dose of sewage sludge. The mineral N and NPK fertilization, used against the background of sewage sludge and straw, did not have asignificant impact on the shaping of the analyzed soil fertility indicators.