## 1 Introduction  
Within the past century, a systematic growth in agricultural production has been observed, mainly due to fertilization, which results in an increased availability of plant nutrients [1]. The availability of macro- and micro-elements, such as Ca, S, Mg, K, N, P, and Fe, is crucial for the proper course of plant life processes that directly contribute to plant growth and yield [2]. Maize is a plant with high potential yield, which requires incurring the costs associated with fertilization, as well as suitable weather conditions during the growing season. A deficiency of nutrients in the early stages of maize growth is the main reason limiting its yield. As reported by [PERSON] et al. (1996) [3], maize during this period takes up minerals only if they occur in sufficiently high concentration in soil, due to the poorly developed root system. In turn, the rapid development of the root system is possible if the plant is provided with an adequately high concentration of nitrogen and phosphorus in soil solution [4; 5; 6]. The relationship between the level of mineral fertilization and the amount of obtained crop yield is obvious, because no other factor shows such a high correlation with yield. From the total mass of nutrients introduced with the applied fertilization, only a part is effectively utilized by plants, and the efficiency of the nutrient uptake varies depending on the element. It is estimated that nitrogen utilization by plants is 50%, and that of phosphorus and potassium is 25% and 60%, respectively. One way to increase the availability of nutrients for plants is row fertilization located in close proximity to seeds, which when applied together with sowing is called initial. This approach of applying the fertilizer causes greater availability of nutrients and thus contributes to the stimulation of a plant's initial growth, but is also safer for the environment [7; 8; 9]. This applies especially to phosphorus, for which uptake can be significantly reduced due to various environmental conditions, causing inhibition of maize growth and development [7]. Another method is via utilized foliar fertilization, which results in a reduction of the overall dose of fertilizers and an increase in their use by providing plants nutrients in accordance with their needs in specific development phases [9; 10]. This system allows for the precise supply of nutrients in accordance with the specific requirements of the plants in doses that are many times smaller than those supplied by the soil system (where they can be absorbed or blocked). Foliar fertilization can also be an effective way to correct deficiencies, especially of micronutrients, which sometimes results in an increase in yield and improvement of quality. Foliar fertilization, in addition to the positive effect documented in the literature, may also include adverse phenomena, such as withering of leaves as a result of the direct application of these fertilizers, which reduces the effective surface of the leaves and thus the efficiency of photosynthesis [11]. The proper growth and development of plants depends on the course of physiological processes, and mainly on the efficiency of photosynthesis. Measurements and testing of chlorophyll content in leaves (an accurate and convenient method for determining photosynthesis), among others tests, can be used to evaluate the effects of various factors on plants, including fertilizers applied to plant leaves [12; 13; 14; 15; 16]. Photosynthetic carbon assimilation is a key process for plant metabolism and is closely related to environmental conditions. Photosynthesis consists of two main parts: the photochemical processes running at the level of thylakoid membranes producing NADPH and ATP, as well as CO\({}_{2}\) reduction pathways (mainly the Calvin cycle) using ATP and NADPH for CO\({}_{2}\) assimilation [2]. A nutrient deficiency directly affects the photosynthetic apparatus, mainly through biosynthesis and the functioning of key photosynthetic components.