No abstract

Digestate is a residue of the anaerobic decomposition of organic waste for biogas extraction, but it can be reused as a source of nutrients. To examine the effect of digestate in kohlrabi production, field experiments were conducted during three seasons in two calendar years. The fertilization treatments included the application of solid digestate (two rates—DS1 and DS2), liquid digestate (two rates—DL1 and DL2), solid manure (two rates—MS1 and MS2), and mineral fertilizer (NPK) and were compared with a plot without fertilization (Ø). The results showed a significant increase in the yield with the use of solid and liquid digestate, as well as with NPK, in all growing seasons, while the microelement contents (Zn, Mn, and Cu) in the leaves were at optimum level. The applied treatments did not increase the plant-available nutrients (AL-P2O5, AL-K2O, Fe, Cu, and Zn) in the soil (except Mn). The application of DL2, MS1, and MS2 led to a higher Pb content in kohlrabi stems compared to the control, but the Pb content remained below the maximum permitted limit. Our research showed that digestate can be used as a valuable source of nutrients for kohlrabi production, with a low risk of soil and plant contamination by heavy metals. However, the control of soil, digestates, and manure quality is recommended.

Although plants have a natural potential for removing various types of pollutants from nature, phytoremediation is a relatively new area of research and has a commercial application. By intensive application of nitrogen fertilisers and pesticides in agriculture, their excessive amounts reach the soil and accumulate or flow into deeper layers of soil and groundwater. So far, most soil remediation studies have been done with herbaceous plants, but they have not shown high efficiency. The paper gives an overview of the possibilities and advantages of using woody plants in the phytoremediation of soils contaminated with nitrates and pesticides. The choice of woody species that can be successfully applied is limited and the best results were obtained with poplars and willows. Unlike nitrates, which are easily absorbed by trees, pesticides are complex organic compounds and their remediation takes place through mechanisms such as rhizodegradation and phytodegradation. Poplar, as the most commonly used woody species for phytoremediation, has shown high efficiency in removing nitrates and pesticides, especially herbicides. Examples of successful soil and groundwater remediation can be found in the remediation of atrazine, alachlor, metribuzin, paraquat and others.