Production of a complex organomineral fertilizer based on local raw materials

Tadqiqotda kompleks organomineral o‘g‘it ishlab chiqarish uchun potensial xomashyo bo‘lgan Markaziy Qizilqum fosforiti, fosfogips va sapropelning kimyoviy tarkibi baholanadi. Sapropel tarkibida 21,52 % organik modda va 1,50 % azot, shuningdek, P, K, Ca, S va Mg aniqlandi. Fosforit tarkibida 17,54 % P2O5 va 47,75 % CaO, fosfogips tarkibida esa 47,60 % SO3 va 32,61 % CaO aniqlandi. Natijalar ushbu xomashyo turlarining tarkibi bir-birini to‘ldirishini ko‘rsatadi va N-P-K-Ca-S tutuvchi organomineral o‘g‘itni keyingi bosqichda ishlab chiqish uchun kimyoviy asos yaratadi.

R E S E A RC H F O C US xalqaro ilmiy jurnali hamkorligida

QR-kod maqolaning DOI sahifasini ochadi SAHIFALAR TIL 863–866 Ingliz

Nasiba Esemuratovna Khalmuratova. Production of a complex organomineral fertilizer based on local raw materials // «O‘zbekiston olima ayollarining mamlakat taraqqiyotiga qo‘shayotgan hissasi» mavzusidagi xalqaro ilmiy-amaliy konferensiya materiallari (Nukus, 2026-yil 9–10- oktyabr). – Nukus, 2026. – B. 863– 866. – DOI: https://doi.org/10.66073/ ReFocus-Conf/0910171

«O‘zbekiston olima ayollarining mamlakat taraqqiyotiga qo‘shayotgan hissasi» XALQARO ILMIY-AMALIY KONFERENSIYA NUKUS, 9–10-OKT YABR 2026

PRODUCTION OF A COMPLEX ORGANOMINERAL FERTILIZER BASED ON LOCAL RAW MATERIALS

Nasiba Esemuratovna Khalmuratova Karakalpakstan Branch of the Academy of Sciences of the Republic of Uzbekistan Karakalpak Research Institute of Natural Sciences, Abdirov prospect 1, 230101 Nukus, Karakalpakstan, Uzbekistan

Abstract: This study evaluates the chemical composition of Central Kyzylkum phosphorite, phosphogypsum, and sapropel as potential raw materials for complex organomineral fertilizer production. Sapropel contained 21.52% organic matter and 1.50% nitrogen, together with P, K, Ca, S, and Mg. Phosphorite contained 17.54% P2O5 and 47.75% CaO, while phosphogypsum contained 47.60% SO3 and 32.61% CaO. The results demonstrate the

complementary composition of these raw materials and provide a chemical basis for further development of an N-P-K-Ca-S containing organomineral fertilizer. Keywords: organomineral fertilizer, Central Kyzylkum phosphorite, phosphogypsum, sapropel, chemical composition, local raw materials. Introduction The rational utilization of local mineral raw materials, recycling industrial by-products, and combining mineral and organic components into a single product are key scientific and practical focuses in developing more effective agricultural fertilizers. The scarcity of phosphate raw materials has especially heightened interest in processing low-grade phosphorites and in the comprehensive use of secondary phosphorus resources [1-3]. Central Kyzylkum phosphorites serve as a vital raw material source for phosphorus fertilizer production in Uzbekistan. Notably, these phosphorites contain significant quantities of calcium- and carbonate-containing compounds alongside phosphates. Studies have shown that different fractions and by-products of Central Kyzylkum phosphorites can be utilized for mineral fertilizer manufacturing, including the partial decomposition with mineral acids to enhance the amount of plant-accessible phosphorus forms [1, 2, 4]. Phosphogypsum is a major by-product of the phosphate fertilizer industry, mainly composed of calcium sulfate dihydrate. It is notably valuable as a secondary mineral resource rich in calcium and sulfur [5, 6]. However, its chemical makeup varies depending on the original phosphate raw material and processing methods, potentially including residual phosphorus- and fluorine-based compounds and other impurities. Therefore, analyzing its chemical composition is crucial before utilizing phosphogypsum as a fertilizer component [5, 6].

Adding an organic component to a complex fertilizer enables the integration of mineral nutrients with organic matter within one system. In this context, sapropel stands out as a promising natural organomineral raw material. Its makeup varies depending on formation conditions and, besides organic and mineral matter, it can contain nitrogen, phosphorus, potassium, calcium, and other elements [7]. NUKUS · 2026

Consequently, accurately determining its chemical composition is crucial when assessing its suitability for fertilizer production. Although Central Kyzylkum’s phosphorite, phosphogypsum, and sapropel differ in origin and chemical makeup, their nutrient components can complement each other. Phosphorite mainly provides phosphorus and calcium, phosphogypsum X A L Q A R O I L M I Y- A M A L I Y K O N F E R E N S I YA

supplies calcium and sulfur, and sapropel offers organic matter along with various macro- and micronutrients depending on its composition. Therefore, comparing their chemical compositions is a crucial first step in assessing the possibility of producing a comprehensive organomineral fertilizer from these materials. This study aimed to analyze the chemical composition of Central Kyzylkum phosphorite, phosphogypsum, and sapropel, and to preliminarily evaluate their potential combined use as mineral and organic raw materials for producing a complex organomineral fertilizer. Materials and methods « O ‘ Z B E K I S T O N O L I M A AY O L L A R I N I N G M A M L A K AT T A R A Q Q I Y O T I G A Q O ‘ S H AY O T G A N H I S S A S I »

The study materials included Central Kyzylkum phosphorite, phosphogypsum, a byproduct of phosphate fertilizer production, and natural organomineral sapropel. These were chosen for their chemical composition and potential roles in creating a complex organomineral fertilizer. Phosphorite provides phosphorus and calcium, while phosphogypsum is a secondary mineral rich in calcium and sulfur. Sapropel, a natural substance, contains organic matter along with macro- and secondary nutrients important for plant growth. In the initial phase of the study, the focus was on analyzing the chemical makeup of the raw materials. Sapropel was tested for organic matter, total nitrogen, phosphorus, potassium, calcium, sulfur, magnesium, carbonate content, ash, moisture, and pH. In phosphorite, the determined components included SiO2, Al2O3, Fe2O3, MgO, P2O5, CaO, SO3, and CO2, while in phosphogypsum, measurements covered P2O5, SO3, CaO, MgO, Al2O3, Fe2O3, SiO2, moisture, and pH. For comparison of agrochemical qualities, the elemental contents of P, K, Ca, S, and Mg in sapropel were also converted stoichiometrically into P 2O5, K2O, CaO, SO3, and MgO equivalents. Results and discussion Chemical analysis of the starting raw materials showed that sapropel differs fundamentally from the mineral components. It contained 21.52% organic matter and 1.50% nitrogen. The measured elemental contents were 0.80% P, 3.18% K, 17.90% Ca, 0.94% S, and 0.11% Mg. For fertilizer-oriented presentation, these values correspond to 1.83% P2O5, 3.83% K2O, 25.05% CaO, 2.35% SO3, and 0.18% MgO, respectively. The pH was 8.31 and the ash content was 76.90%.

Table 1. Chemical composition of sapropel Organic N, P2O5, K2O, CaO, SO3, MgO, CO2, Ash, Moisture, № matter, pH % %* %* %* %* %* % % % %

1 21.52 1.50 1.83 3.83 25.05 2.35 0.18 15.70 76.90 8.31 1.58 NUKUS · 2026

The presence of N, P, K, and organic matter suggests that sapropel is not just an organic filler but also a source of nutrients in the complex fertilizer. The potassium content stands out, as the other mineral components examined are not X A L Q A R O I L M I Y- A M A L I Y K O N F E R E N S I YA

major potassium sources. Additionally, the high calcium-equivalent level points to a significant calcium-bearing mineral fraction in the sapropel. The Central Kyzylkum phosphorite's chemical composition included 17.54% P2O5 and 47.75% CaO. The raw material also contained 16.50% CO 2, 4.06% SO3, and 1.79% MgO, along with smaller quantities of SiO₂, Al2O3, and Fe2O3. Table 2. Chemical composition of Central Kyzylkum phosphorite SiO2, Al2O3, Fe2O3, MgO, CaO, SO3, CO2, № P2O5, % % % % % % % %

1 1.24 0.95 0.73 1.79 17.54 47.75 4.06 16.50 « O ‘ Z B E K I S T O N O L I M A AY O L L A R I N I N G M A M L A K AT T A R A Q Q I Y O T I G A Q O ‘ S H AY O T G A N H I S S A S I »

The P2O5 content shows phosphorite as the main phosphorus source in the proposed fertilizer. Meanwhile, high levels of CaO and CO 2 are significant for the upcoming nitric acid processing stage. Since carbonate components react with nitric acid, both the P2O5 level and the carbonate fraction in the raw material should be taken into account when determining HNO3 dosage in future studies. Analysis of phosphogypsum revealed that its main constituents were SO 3 at 47.60% and CaO at 32.61%. It also included 1.62% P2O5, 0.22% MgO, and 2.08% SiO₂. The moisture content ranged from 18% to 20%, and the pH level varied between 4.5 and 5.3. Table 3. Chemical composition of phosphogypsum P2O5, SO3, CaO, MgO, Al2O3, Fe2O3, SiO2, Moisture, № pH % % % % % % % %

1 1.62 47.60 32.61 0.22 0.71 0.14 2.08 18-20 4.5-5.3

The elevated levels of SO3 and CaO suggest that phosphogypsum could serve as a source of sulfur and calcium for the suggested organomineral fertilizer. Additionally, remaining P2O5 might help balance the phosphorus content in the final product. The combined evaluation of the three raw materials suggests they can work together functionally. Phosphorite supplies P and Ca; phosphogypsum provides Ca and S; and sapropel organic matter provides N and K, along with additional P, Ca, S, and Mg. In the next technological phase, nitric-acid activation of phosphorite could also add nitrate nitrogen. When this nitrate–phosphate compound is combined with phosphogypsum and sapropel, it creates a foundation for developing a complex organomineral fertilizer that includes N-P-K-Ca-S and organic matter. Chemical analysis indicates that Central Kyzylkum’s phosphorite, phosphogypsum, and sapropel are complementary raw materials. Phosphorite contains 17.54% P2O5 and 47.75% CaO, highlighting its function as a source of NUKUS · 2026

phosphorus and calcium. Phosphogypsum’s 47.60% SO3 and 32.61% CaO suggest it could be a secondary source of sulfur and calcium. Meanwhile, sapropel differs from the mineral components by encompassing 21.52% organic matter, along with N, P, K, Ca, S, and Mg. These findings provide a preliminary chemical basis for further research on X A L Q A R O I L M I Y- A M A L I Y K O N F E R E N S I YA

combining these raw materials to develop a complex organomineral fertilizer that includes organic matter and N-P-K-Ca-S nutrients. Future studies will focus on the conditions for nitric-acid activation of phosphorite, the optimal ratios of phosphogypsum to sapropel, and the physicochemical and agrochemical characteristics of the resulting fertilizer.