Abstract
This study shows the influence of compost fertilization derived from sludge obtained from wastewater treatment on the nutrition of an eight-year-old apple orchard, ʹJonathanʹ cv. A field experiment was conducted to demonstrate the beneficial and negative aspects of (urban) sludge compost fertilization in apples and to assess the risk of soil contamination with heavy metals from municipal sewage sludge compost. The experimental factor was the compost with the following gradations: V1 = 0 t/ha, V2 = 20 t/ha, V3 = 40 t/ha, V4 = 60 t/ha, V5 = 80 t/ha. After two years (2019-2021) from soil fertilization with compost, the nitrogen content of the leaves increased in the treatment with the maximum fertilization dose (80 t/ha) by 30% compared to the unfertilized control, while the phosphorus content of leaves increased by 80% compared to non-fertilization control. The potassium content of the leaves increased by 36% in the 80 t/ha treatment compared to the unfertilized control, but still remained at a deficit level. The results showed that growth and yield were improved by using sewage sludge compost. However, sewage sludge compost applications have not significantly altered the heavy metal content of plant tissues. The concentration of heavy metals in the soil did not exceed the maximum permissible thresholds according to standards established in other EU countries, where compost from sewage sludge is considered product, not waste. However, the calculation of the Igeo index (geoaccumulation index of heavy metal in soil) showed certain levels of soil pollution already installed with Cd Zn, Pb in all variants fertilized with compost.
Highlights
IntroductionDue to the nutrient content and the important intake of organic matter, large amounts of sludge can be used in fruit growing as fertilizer
In order to minimize the negative effects of residual sludge on a soil, the characteristics of a given sludge and the critical concentrations of heavy metals must be taken into account
The objective of this study is to evaluate the effect of applying different doses of compost from urban sludge derived from wastewater on soil fertility and tree nutrition, in a seven-year apple plantation, ʹJonathancultivar, in order to reduce residual deposition and to prevent degradation of the environment
Summary
Due to the nutrient content and the important intake of organic matter, large amounts of sludge can be used in fruit growing as fertilizer. The application of residual sludge in fruit growing is an inexpensive method and is in line with the ecological principles of waste recycling, and at the same time can be a method of improving the physical, chemical and biological properties of the soil (Benitez et al, 2001). In order to minimize the negative effects of residual sludge on a soil, the characteristics of a given sludge and the critical concentrations of heavy metals must be taken into account. In the use of dehydrated sludge as fertilizer in agriculture, a number of issues related to its content in heavy metals, contaminant organic substances and pathogens remain to be solved
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