Effect of the biostimulant Kelpak SL on the content of some microelements in two grass species

Seaweed extracts have been recently introduced to crop growing, particularly to sustainable agriculture, in many countries worldwide. However, our knowledge of the action produced by Kelpak is only fragmentary as it is influenced by a number of factors, for example crop plant species and extract application schedule. Our objective was to determine the effect of Kelpak SL on the content of selected microelements in two grass species. A field experiment was arranged in a randomized subblock design (split-split-plot) with three replicates. It was conducted at the Experimental Unit of the University of Natural Sciences and Humanities in Siedlce (Poland) and started in late April each year. The following factors were examined: pure stands of two grass species Dactylis glomerata L. (cv. Amila) and Festulolium braunii (K.Richt.) A. Camus (cv. Felopa) grown in a monoculture, a biostimulant distributed under the trade name Kelpak SL, applied at 2 dm3 ha-1 (no biostimulant in the control treatment), and nitrogen applied at 50, 100, 150 kg ha-1 (no nitrogen in the control). During the experiment, grass was cut three times a year. The plant material was subjected to chemical analyses to assess dry matter (by determining the moisture content), zinc, copper, iron and manganese. The application of Kelpak significantly increased the Zn, Cu, Fe and Mn content in the grass species tested, regardless of the remaining factors. The grass species did not differ significantly in their content of Zn, Cu, Fe and Mn. The concentrations of the microelements in both species were significantly affected by a dose of nitrogen. At higher nitrogen doses, the concentrations of Zn, Cu and Fe were lower, unlike the content of Mn, which increased. The Fe:Mn ratio in the dry matter of both grasses was 2.79, which indicates some manganese deficiency.