The aim of this study was to determine the content of potassium (K), calcium (Ca) and magnesium (Mg), and the K:(Ca+Mg) ratio in meadow sward irrigated with potato starch and brewery wastewater. The experiment was conducted in the center for wastewater treatment and use in Kupiski-Jednaczewo (approx. 600 ha), which has been equipped with facilities for sprinkler irrigation with wastewater since 1992. Samples of meadow sward were collected for chemical analyses in 1998, 2003, 2008 and 2013. Potato starch and brewery effluents were mixed in a storage reservoir at a ratio of 1:0.4. Meadow sward was irrigated with wastewater in autumn and after the first harvest, at an annual dose of 200-300 mm. On average, wastewater contained (mg dm-3): N – 223, P – 48, K – 285, Ca – 80, Mg – 46, Na – 68. The floristic classification based on the percentage of dominant species (more than 20% in the sward) revealed the following meadow communities: Fr+Ao – Festuca rubra + Anthoxanthum odoratum, Ap – Alopecurus pratensis, Ae – Arrhenatherum elatius, Pha+Gm – Phalaris arundinacea + Glyceria maxima, Dg+Fr – Dactylis glomerata + Festuca rubra, Pp+Dg – Poa pratensis + Dactylis glomerata. The Fr+Ao community developed in the control treatment without irrigation. Meadow sward irrigated with wastewater was characterized by high K content and Mg deficiency, whereas the K:(Ca+Mg) ratio exceeded the recommended upper limit for high-quality fodder. In general, the analyzed floristic types of meadow communities did not differ significantly in their chemical composition, with the exception of the Pha+Gm community, which was characterized by the significantly lowest Mg concentration. The average K content of meadow sward ranged from 18.1 (Fr+Ao) to 36.0 g kg-1 (Ae); the average Ca content ranged from 4.68 (Pp+Dg) to 6.45 g kg-1 (Fr+Ao); the average Mg content varied from 1.05 (Pha+Gm) to 1.50 g kg-1 (Fr+Ao and Pp+Dg), and the K:(Ca+Mg) ratio ranged from 1.04 (Fr+Ao) to 2.64 (Ap).  

24.3.2019