The aim of this study was to determine the content of potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P) and sodium (Na), and the K:(Ca+Mg) and Ca:P ratios in meadow sward irrigated with potato starch and brewery wastewater. The experiment was conducted in the center for wastewater treatment and use in Mątwica-Kupiski (668 ha), which has been equipped with facilities for flood irrigation with wastewater since 1965. Meadow sward was irrigated with wastewater in autumn and after the first harvest, at an annual rate of 200-300 mm. On average, wastewater contained (mg dm-3): N – 144, P – 38, K – 314, Ca – 77, Mg – 47, Na – 76. In 1998, 2003, 2008, 2013 and 2018, before the first harvest, samples of meadow herbage were collected for chemical analyses from characteristic phytocenoses of different floristic types: DcCpPp - Deschampsia caespitosa + Cardamine pratensis + Poa pratensis, PhaRr - Phalaris arundinacea + Ranunculus repens, ApAre - Alopecurus pratensis + Arrhenatherum elatius, ApPp - Alopecurus pratensis + Poa pratensis, Ap - Alopecurus pratensis, ApPha - Alopecurus pratensis + Phalaris arundinacea, ApAr - Alopecurus pratensis + Agropyron repens, PpArDg - Poa pratensis + Agropyron repens + Dactylis glomerata. The DcCpPp community developed in the control treatment without irrigation. Meadow sward irrigated with wastewater was characterized by high abundance of P and Ca, excessively high K content, and Na and Mg deficiency. The Ca:P ratio was desirable, whereas the K:(Ca+Mg) ratio exceeded the recommended upper limit for high-quality fodder. In general, the analyzed floristic types of grassland communities did not differ significantly in their chemical composition; only the PhaRr community was characterized by the lowest K content, the highest Mg concentration and the significantly lowest K:(Ca+Mg) ratio. The average content of the analyzed elements in meadow herbage was as follows: K - from 17.4 (DcCpPp) to 39.2 g kg-1 (ApPha), Ca - from 3.2 (ApAr) to 6.7 g kg-1 (DcCpPp), Mg – from 1.2 (ApAr) to 2.6 g kg-1 (DcCpPp), Na – from 0.6 (ApAr and PpArDg) to 1.3 g kg-1 (DcCpPp), and P – from 2.2 (PhaRr) to 3.6 g kg-1 (ApAr). The K:(Ca+Mg) ratio ranged from 0.8 (DcCpPp) to 3.9 (ApAr), and the Ca:P ratio varied from 1.0 (ApAr) to 2.9 (PhaRr).

25.1.2020