# Evaluation of the Effect of Biostimulation on the Yielding of Golden Delicious Apple Trees
###### Abstract  
The aim of the study was to assess the impact of N Pro and Seactiv Complex technologies based on sea algae extracts on the yield and quality of Golden Delicious apple trees compared to the standard fertilization program. Research conducted in the years 2008-2017 showed that the tree fertilization technology and the year of research had a significant impact on the quality and yield parameters. The abundance of seaweed extracts had a positive effect on the greater number of fruits per tree (pcs), their weight (t \(\times\) ha\({}^{-1}\); kg tree\({}^{-1}\)), the percentage of fruits exceeding 7.5 cm in size (%) and the average weight of fruits (g) compared to the control combination. In most of the analyzed study years, total yield exceeded the 90 t \(\times\) threshold regardless of the fertilization program. The use of technology based on sea algae extracts during 10 years of research had a positive effect on the quality and weight compared to the standard fertilization technology commonly used in cultivation. seaweed extracts; fertilization; fruit quality; fruit firmess; long-term research +
Footnote †: journal: Applied sciences  
Mineral fertilizers, which contain essential nutrients for proper plant development and soil fertility, are used to replenish nutrient deficiencies, allowing for high yields [5]. Mineral fertilization largely contributes to the rapid growth of yields and is the basic agotechnical treatment in horticultural production [6]. In order to increase the effectiveness of this treatment, biostimulants are increasingly used [7; 8; 9]. Biostimulants are currently viewed primarily as an additive to mineral fertilizers to promote uptake, increase resistance to abiotic stresses, and influence plant growth [10]. It has been proven that biostimulants can increase nutrient uptake efficiency by regulating the expression of transcription factors and genes [11]. The use of biostimulants is considered a good practice to reduce fertilizers and other chemicals, resulting in less environmental damage and is part of sustainable agricultural development [9]. Biostimulants manufactured from raw materials of natural origin, which are based on, among other things, seaweed extracts, micro-organisms, humic acids and protein hydrolysates [12; 13], are considered to be environmentally friendly, which is particularly important in sustainable plant cultivation [14]. The popularity of seaweed-based preparations continues to grow rapidly, mainly due to their phytostimulant properties, phytoelicitor activity, initiation of phytohormal reactions, and positive effects on changes in soil and plant microbiome components [15]. It is believed that the maximum potential for the use of seaweed, which is considered a biological resource, has still not been reached. This also applies to biostimulants based on these raw materials, which, due to the lack of sufficient scientific knowledge about them, are still not fully optimally utilized in crop production [16]. Biostimulants based on seaweed extracts are a complex matrix of biologically active compounds [7] that contain large amounts of mostly organic substances, but small amounts of inorganic nutrients. Their composition includes polyphenic compounds, minerals, polysaccharides, amino acids, phlorotannins, lipids, proteins, oxylipins, plant growth hormones, sterols, fatty acids and carotenoids [16; 17]. Seaweeds from three clusters: _Phaeophyceae_, _Rhodophyta_, and _Chlorophyta_[14], are used for commercial agricultural purposes. Among brown seaweeds used for biostimulants, _Ascophyllum nodosum_ (L) is the best-studied species [18]. In order to improve plant production, biostimulation is used, and it is crucial to know the chemical composition of the available products in the market to apply them in appropriate doses and at developmental stages. It should also be noted that each plant species may react differently to a given biostimulant.