Effect of Plant Biostimulation with Pentakeep V Fertilizer and Nitrogen Fertilization on the Content of Macro- and Micronutrients in Spinach*

The aim of the research was to determine the influence of foliar nutrition with Pentakeep V as well as differentiated nitrogen fertilisation on the content of macro(Ca, K, Mg, Na, P and S) and micronutrients (B, Cu, Fe, Mn and Zn) in spinach leaves. Pentakepp V is a fertilizer containing 5-aminolevulinic acid (5-ALA), which is the direct precursor of chlorophyll in plants. In 2006-2007, a pot experiment with spinach Spinacia oleracea L. cv. Spinaker F1 was carried out. The plants were cultivated in 60 × 40 × 20 cm containers placed in an open field under a shade-providing fabric. Containers were filled with loamy clay soil (35% of sand, 28% silt, 37% clay) with the organic matter content of 2.44% in 2006 and 2.52% in 2007. The experiment design included 2 sub-blocks: with and without foliar nutrition. The plants were sprayed twice with Pentakeep V fertilizer in a dose of 0.02% w/v (16 ml 100 dm–3 – 3000 dm3 per 1 ha). In each sub-block, soil fertilization with nitrogen was applied: 1 – control (without N fertilization), 2 – 25 mg N dm–3 of the soil (50% of N dose), 3 – 50 mg N dm–3 of the soil (100% of N dose). Nitrogen fertilization was applied in the form of ammonium nitrate prior to seed sowing. Among all of the determined nutrients, a significant interaction between foliar nutrition and soil application of nitrogen was observed in the case of Ca and Fe content in spinach leaves. Foliar application of Pentakeep V decreased the content of Ca in plants without N fertilization as well as increased the amount of this element in plants fertilized with full dose of nitrogen (100% of N dose). These observations were further verified by the changes of Ca content in soil after plant cultivation. Increased uptake of Ca from soil was observed for plants treated with Pentakeep V and fertilized with the full dose of nitrogen. A higher content of this