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The pepper producers in the Republic of Macedonia have used drip irrigation systems to increase yield in recent years, but more research is still needed, related to irrigation scheduling and precise requirement of nitrogen fertilizer to maximise pepper yield. Therefore, a two year experiment was conducted in a plastic house to determine the nitrogen fertilizer use efficiency (NFUE) and yield potential of pruned pepper as affected by irrigation and fertilization regime. Four experimental treatments were applied in this study. Three of the treatments were drip fertigated (DF1, DF2, DF3), while the fourth treatment was furrow irrigated with conventional fertilization (ØB). The labelled urea with 1% concentration of a stable isotope of nitrogen (15N) was applied for determination of NFUE. The results of this study clearly showed that increased NFUE and pepper yield depend on irrigation and fertilization regime. Namely, NFUE was significantly increased with the application of nitrogen fertilizer through drip irrigation system as compared to conventional fertilization with furrow irrigation. Also, drip fertigation frequency positively affects percentage increase of NFUE. Furthermore, our results showed that drip fertigation treatments resulted in significantly higher pepper yields in comparison to conventional fertilization. Also, drip fertigation frequency at four and two days (DF2 and DF1) resulted in higher yields when compared with drip fertigation scheduled by using tensiometers (DF3). Generally, to reach acceptable pepper yield with high NFUE, we recommend drip fertigation with a frequency of two to four days combined with two main shoots of pruned pepper in order to increase farmer’s income and to minimize the environmental impact.

According to Rinker (2017), Pleurotus species are grown on wood sawdust and plant fibers supplemented with locally available proteins and carbohydrates. The main application of mushroom residues in vegetable production is as a component of growing media (Charles Heuser et al., 2007; Younis et al., 2023 ) for seedling production of crops such as tomato (Medina et al, 2009; Eudoxie and Alexander, 2011; Zhang et al., 2012; Ünal, 2015; Priadi et al., 2016; Collela et al., 2019; Alves et al., 2024), pepper (Medina et al., 2009; Demir, 2017), lettuce (Kwack et al., 2012; Marques et al., 2014; Liu et al., 2018), eggplant (So nmez et al., 2016), cucumber (Zhang et al., 2012), melon (Van Tam and Wang, 2015) and zucchini (Medina et al., 2009). Furthermore, spent mushroom substrate can enhance microbial diversity (Huang et al., 2023), aid in disease control (Mwangi et al., 2024), support biogas production (Kumar et al., 2022), contribute to bioremediation efforts (Rinker, 2017), and serve as a material for biodegradable containers in horticulture (Postemsky et al., 2016). MATERIAL AND METHODS In order to achieve the first objective a detailed analysis of the physical and chemical properties of a spent mushroom substrate of oyster mushroom (Pleurotus ostreatus) was conducted at the accredited Laboratory for Soil and Fertilizer Analysis (L-04), Faculty of Agricultural Sciences and Food - Skopje.

Cluster analysis was performed using Ward's method and Euclidean distance as the dissimilarity measure to identify similarities among soil parameters. According to the global review by (Neaman et al., 2024), soil Cu concentrations are directly proportional to precipitation and inversely related to the aridity index (the ratio of potential evapotranspiration to precipitation). The study confirmed that climate, farm age, and soil organic matter content are the three key factors explaining the variability of Cu in agricultural soils worldwide. [...]increased rainfall enhances Cu losses via surface runoff, but at the same time increases the use of Cu fungicides, resulting in a net positive relationship between precipitation and soil Cu levels in humid regions. The most important sources include the use of copperbased fungicides, the application of liquid fertilizers, the discharge of sewage sludge, industrial activities, mining, emissions of particles from car brakes, and atmospheric deposition of copper (Halamic et al., 2001; Mitkova et al., 2005; Prentovic et al., 2009; Matse et al., 2024).The accumulation of copper in soil depends on various parameters, primarily on the physicochemical properties of the soil (pH, soil structure, organic matter content, clay content, Fe content) (Kelepertzis et al., 2015; Jeon et al., 2024).

This paper is a result of many years of field and laboratory research of the soils in Crna River Basin, spread out on 497 514,81 ha, with the altitudes ranging from 150 to 2601 m above sea level with the main goal of gaining better understanding of the productive capacities of soils and soil conservation measures for their improvement. The catchment area of the Crna River is a spatial area that extends in two states in the southwest of the Republic of North Macedonia and the northern part of the Republic of Greece. The filed research of the soils and preparation of soil samples has been done according to ISO 10381-1 and ISO 10381-2 protocols. Soil samples were analysed in the laboratory: hygroscopic moisture; mechanical composition; pH of the soil solution; humus content and total nitrogen; content of carbonates; available nutrients P2O5 and K2O. The mechanical composition and chemical properties of the soils were determined by standard methods. Physical-geographical conditions of the studied area are heterogeneous, with numerous relief forms; different expositions and inclinations, and with great differences of altitude. There are several geological formations of a very heterogeneous petrographic-mineralogical composition and climate-vegetation zones. Long-term effects of human participation should also be noted. The vast diversity of the factors required for soil formation in the catchment area of the Crna River are the reason for the formation of many different soil types as well as the lower taxonomic units. There are 14 (fourteen) different soil types distributed in the Crna River Basin together with a considerable amount of subtypes, varieties and forms. The most significant soil types are: Fluvisol and Cambisol. These types of soils are characterized by different properties (chemical, physical, physical-mechanical and productive). Therefore, they have varied effects on agricultural production (field crop, viticulture and fruit production). The aim of this research was to present combined measures of soil conservation for soils from mountain terrains, lake terraces and undulating-hilly terrains, including from sloping terrains and from plain terrains, based on the research that was implemented.

This paper is a result of many years of field and laboratory research of the soils in Pčinja river basin, North Macedonia, spread out on 237.640,71 ha ranging from 191 to 1664 m above the sea level in order to gain a better understanding of the productive capacities of the soils and measures for their improvement. The catchment area of Pčinja River is a spatial area that extends in two states in the of the Republic of North Macedonia and the part of the Republic of Serbia, whose boundaries are naturally clearly defined. Soil samples were taken by spade and one composite sample was prepared for each sampling site, each containing about 3 kg of soil. Before sieving the samples were air dried. In laboratory, the following analyses have been carried out on the soil samples: hygroscopic moisture, mechanical composition, pH of the soil solution, humus content and total nitrogen, content of carbonates. The mechanical composition and chemical properties of the soils have been determined by standard methods. This area is very heterogeneous, with numerous relief forms, with different expositions and inclinations, and with great differences of altitude. Additionally, there are several geological formations of a very heterogeneous petrographic-mineralogical composition and climate-vegetation zones. Long-term effects of human involvement should also be noted. The vast diversity of the factors required for soil formation in this area is the reason for the formation of many different soil types as well as the lower taxonomic units. These types of soils are characterized by different properties (chemical, physical, and physical-mechanical, productive). Therefore, they have varied effects on agricultural production. There are 9 different soil types and 18 complexes of more than two land types distributed in the Pčinja River basin together with a considerable amount of subtypes, varieties and forms. The most represented with the largest area are: Vertisol, Fluvisol, Fluvisol (Colluvial Soils) and Cambisol.

A various organic solvents were tested (methanol, ethanol, ethyl acetate and acetone) and their different concentrations (20, 40, 60 and 80%) in order to establish optimum solvent concentration for extraction of polyphenols from onion. RESULTS AND DISCUSSION This study evaluated total polyphenolic content (TPC) after optimization of extraction of polyphenols from onion using different concentration of conventional organic solvents (methanol, ethanol, acetone and ethyl acetate) and different times. According to the literature the Folin-Ciocalteu assay is used for TPC determination in different fruits and vegetables, as it is case in the work of Llupa and coworkers (2022). [...]of reaction of polyphenolic compounds with Folin-Ciocalteu reagent blue complex was formed with absorption maximum in the visible region around 760 nm, and it can be quantified by visible spectrophotometry (Kamboj et al, 2015).

[...]they have varied effects on agricultural production. [...]soils of the plains occupy 17.784,4 ha (12.01%) and Urbisol 1.755,57 ha (1.18%). [...]they have varied effects on agricultural production. The soils on this terrain (relief) form have the following common properties: a) very pronounced erosion (occurrence of Regosols and erosion of horizon A or part thereof, in the soils with A-C, A-(B)-C and A-E-B-C profile type); b) absence of compact rocks as substrate and soil genesis over clastic sediments, resulting in deep solum and physiologically active profiles; c) greater presence of clay resulting from the substrate or the argilogenesis within the profile; d) presence of smectites in some soils (Vertisols) arising mainly from the substrate and partially from the soil genesis, and in relation to that, deterioration of the physical properties of the soils; e) occurrence of textural differentiation at some soils (Vertisols and Albic Luvisols), and in relation to that, deterioration of the physical properties; f) greater presence of the silicate - carbonate substrate in the soil genesis, in comparison to the substrate of the mountainous terrains; g) relative dryness of the soils (which is lower at the lake terraces), caused from insufficient quantity of rainfalls, surface water flow and very deep underground water; e) insufficient quantity of humus and nutrients (especially N and P); f) relatively good chemical properties (the high content of carbonates of Humic Calcaric Regosols and the acidity of the Albic Luvisols are an exception). In order to increase their productive ability, the following joint measures should be undertaken according to relief forms: - Joint measures for soils from mountain terrains: (protection from erosion, fertilization with organic and mineral fertilizers, proper tillage, liming if necessary); - Joint measures for soils from lake terraces and undulating-hilly terrains: (deep tillage, humization: organic fertilizers and phytomeliorations, intensive use of mineral fertilizers N and P2O5, and for plants that need potassium during the entire year and for obtaining much higher yields and K-fertilizers, anti-erosion measures, proper irrigation method); - Joint measures for soils from sloping terrains: (anti-erosion protection measures, irrigation, humization, intensive use of mineral fertilizers); - Joint measures for soils from plain terrains: (regulation of the water regimen, lowering of the level of underground water-drainage, tillage and creating a deep fallow, fertilization with mineral and organic fertilizers with previous soil fertility control, proper irrigation).

The aim of this study was to determine the content of physiologically active potassium (K2O) in the soil in the territory covered by the work of the Agricultural Advisory and Expert Service of Smederevo (PSSS Smederevo). Research was carried out on three locations: Velika Plana, the City of Smederevo and Smederevska Palanka, for the purpose of ensuring the optimal use of mineral and organic fertilizers, to preserve soil resources. The paper presents the results of testing the content of physiologically active potassium - K2O. The territory of Velika Plana had most areas with harmful content, while the lowest content of K2O was recorded in the territory of Smederevska Palanka. The results indicate that the obtained values were greatly influenced by different types of soil on the examined plots, and an anthropogenic factor was also evident. All the plots from which soil samples were taken for analysis of potassium content were mapped, and based on the obtained results farmers were given advice on the necessary remedial measures and optimal use of organic and mineral fertilizers to improve agricultural production and preserve biodiversity. Mineral nutrition is extremely important for growth, development and reaching maximum yields of cultivated plants.foliar mass were higher in the PSB version (without fertilizers), and in the treatment with the use of P. polymyxa - with the use of N20P40 fertilizers.

Due to the stated importance of the mechanical composition and organic matter of the other properties of soil, this paper investigates the impact on retention of soil moisture at different points of tension, ranging from 0.33 up to 15 bars, which correspond to the water constant, which is called permanent wilting point (PWP). There has been descriptive statistics (average value, standard deviation and variation coefficient were determined) of the mechanical composition, chemical properties and constants of soil moisture in Microsoft Excel. The presented data on the mechanical composition of Rendzina Calcaric Regosol are similar to the data for this soil type as presented by (Filipovski, 1996; Kalicka, et al. 2008). Besides the mechanical properties, the retention of soil moisture in the Rendzina Calcaric Regosol is strongly influenced by the chemical properties. According to Filipovski (1996) the average content of humus in the horizon Amo analysed for 481 profiles of Rendzina Calcaric Regosol in