The risk of using fermented biowaste for the fertilisation of haylage oats

The yields of oats used for making hay and the content of some heavy metals (Cd, Zn) in the aboveground biomass were studied in a three-year pot experiment. The experiment had the following variants: Variant 1 - control (without dressing); Variant 2 - farmyard manure; Variant 3 - compost from the city of Cracow (consisting of wood chips, grass, leaves, vegetable residues, and tobacco) and Variant 4 - compost from Cerveny Ujezd (consisting of sewage sludge from a sewage disposal plant in Prague, straw and poultry droppings). The aforementioned fertilisers were used in a single application before sowing in 2001. Doses of individual organic materials were applied in the following final doses of N, P and K nutrients per pot: 1.5 g; 1.1 g; and 1.75 g, respectively. In the 2nd and 3rd year of the experiment, only nitrogen (as ammonium nitrate) was applied into all pots in a dose of 0.75 g N. Composted biowaste is an organic fertiliser comparable to manure. Within the first two years of this experiment the highest yields were obtained in Variant 4, which contained poultry droppings. In Variants 2 and 3 the release of nutrients was slower but the average yields for a three-year period were similar to Variant 4 and significantly higher than the untreated control (Variant 1). The comparisons of the individual years showed that the yields were significantly the highest in the 2nd year due the maximum release of nutrients. The analysis of accumulation of Cd and Zn in oat plants demonstrated that the detected amounts were not higher than the limit contents of Cd issued in the Guidelines of the Czech Ministry of Agriculture No. 451/ 2000 of the Collection of Laws, as well as the limits for dry fodder.