The studied mountain brown soils are characterized by loamy granulometric composition, nutty-cloddy structure, slightly acidic or slightly alkaline reaction. The total potassium content in the upper horizon varies from 1.240 to 1.685 %. Exchangeable potassium ranges from 265 to  1028 mg/kg of soil. The share of clay fraction varies from 2.9 to 18.3 %. In silty fractions, the con- tent of potassium is 2-3 times higher than in the soil as a whole and ranges from 1.26 to 3.02 %. Potassium reserves were identified - near, immediate and potential. Fluctuations in the content of potassium reserves in the humus horizon of the total content were: immediate from 1.5 to 8.31 %, near ө from 5.40 to 32.85 %, potential, dominant in the total content 65.12 to 93.0 %. It has been established that the distribution of potassium and its reserves in the pasture mountain brown  soils of Uzbekistan is uneven and depends on many natural factors. It was revealed that potassium of a potential reserve is presented in a sufficiently large amount, and in a slightly smaller amount - near and immediate. Losses of near and immediate reserves of potassium lead to a decrease in the content of total potassium in general.

The article shows that in the agro-industrial complex of Northern Kazakhstan, much attention is paid to the issues of progressive improvement of soil fertility, crop yields, increasing the production of grain, feed and other crops based on a scientifically based farming system. Currently, the acreage should be carried out in the crop rotation system and a special place is occupied by the problem of providing the population with high-protein and balanced fatty foods. The introduction of oilseed flax into diversified types of field crop rotations contributes not only to providing the national economy with oilseed products, but also to improving the agrophysical, biological and agrochemical properties of ordinary chernozems. In addition, flaxseed contains a large amount of balanced and easily digestible protein, vegetable oil, various sugars and carbon waters, as well as essential vitamins and trace elements needed in the diet. Field experimental studies were conducted to identify the effect of the effectiveness of mineral and organic fertilizers on improving soil fertility, the formation of the size and quality of flax crops, and to determine the most effective option in the northern region of Kazakhstan. The optimal use of mineral and organic fertilizers caused a positive effect of flax plant cenosis on the density, in particular, on the field germination of plants, plant growth dynamics, accumulation of raw and dry mass of flax plants. The optimal use of mineral and organic fertilizers contributed in addition to increasing soil fertility on plant yields and profitability of growing oilseed flax.

The use of mineral fertilizers is an important agronomic technique in the system of intensive agriculture. In 2021-2022, field experiments were conducted in the Maktaaral district of Turkestan province to assess the response of mid-season melon to different doses and ratios of nitrogen, phosphorus and potassium fertilizers. To model the effect of fertilizers and soil salinity on the indicators of yield and nutrient use by melon plants, the data by years were subjected to mathematical processing separately in order to build the most adequate regression models describing the dependence of the resulting factors on the studied factors against the background of the real state of soil fertility. In the first year of research, the early melon yield was 96% dependent on the combined effect of all factors studied. At the same time, nitrogen fertilizer had a separate positive effect, but the effect of its interaction with phosphorus and salt was negative. Potassium combined with phosphorus accelerated melon's early maturity, but in interaction with salt it slowed it down. The gross yield of melon was 92 % dependent on the combined effect of the studied factors, with nitrogen separately and in combination with phosphorus and phosphorus combined with potassium showing a positive effect. The dependence of nitrogen removal per unit of melon yield on the studied factors was 99 %, phosphorus – 88 % and potassium – 78 %. In the second year of research, the early harvest of melons was 97 % dependent on the total effect of all the studied factors. Nitrogen fertilizers had a positive effect, while phosphorus and soil salinity had a negative effect. Nitrogen interaction with phosphorus and soil salinity had a negative effect. Potassium in interaction with phosphorus had a positive effect on early melon yield, but in interaction with soil salt it was negative. The gross yield of melon was 90% dependent on the combined effect of all 4 studied factors. The combination of nitrogen nutrition with potassium and soil salinity had a negative effect, while phosphorus combined with potassium had a positive effect on melon gross yield.  Nutrient removal by a unit of melon yield responded adequately to changes in the studied factors (R²=0.84-0.90) in the second year of the study. Application of nitrogen fertilizer increased normative removal of nitrogen, phosphorus and potassium.

In arid and sharply continental soil and climatic conditions of the Akmola region, green-house farming is an important technique. Greenhouse farming is one of the promising areas of agriculture, since vegetable and melon crops are grown in conditions of temperature, humidity, illumination, and nutrient medium regulated at an optimal level, which results in a high yield of fruits, vegetables and melons. In the winter industrial greenhouse of Kokshetau University, the effect of mineral fertilizers and trace elements on the growth, development and yield of cucumber was studied. As a result of two crop rotations, positive data were obtained indicating an increase in plant growth in height at the early stages of vegetation by an average of 2.20 cm with presowing soaking of seeds and non-root fertilization of plants with 0.1-0.5 % aqueous solution with preparations of biological origin Phomazin+Filvimax, an increase in leaf area by 13.5 cm², an acceleration of the flowering phase by 1.3-1.5 days, an increase in the yield of standard fruits by 22 pcs., an increase in yield by 5.9 kg / m². The improvement of these indicators is justified by the presence in the preparations of biological origin Phomazin+Filvimax of a significant amount of macro- and microelements that play an important role in plant nutrition and the formation of cucumber fruits. It is recommended to grow vegetables according to the developed technology in a greenhouse in the conditions of the Akmola region for uninterrupted supply of fresh vegetables to the population.

Organic vegetables and potatoes are not produced in Kazakhstan. In this regard, the development of organic agricultural technologies is very important. Mineral fertilizers cannot be used  in organic production. There are difficulties in preserving and increasing soil fertility, providing vegetables with all the necessary elements of nutrition. Therefore, the role of organic fertilizers and biological stimulators increases in soil and plant formation. Organic fertilizers are an important factor in preserving and increasing soil fertility, increasing yields, and improving quality, including the ecological purity of products, potatoes, and vegetables. The influence of local organic fertilizers, a new bio-organic fertilizer Baraebong Organic Fertilizer (Republic of Korea), and biological products on the nutritional regime of the soil and the productivity of potatoes and root crops (carrots and beets) was studied on the dark chestnut soil of the foothill zone of the south-east of Kazakhstan. Scientific research was carried out at the experimental station of the Regional branch "Kainar" LLP "Kazakh Scientific Research Institute of Fruit and Vegetable Growing". The research uses “The Methodology of Agrochemical Research”, “The Methodology of Experimental Work in Vegetable Growing and Melon Growing”, ‘The Methodology of Field Experience in Vegetable Growing”, and the methodological recommendations "Transition from Traditional to Bioorganic Farming in the Republic of Belarus". The positive effect of different types of bioorganic fertilizers on the nutritional regime of the soil was established such as the content of mobile forms of nitrogen, phosphorus, and potassium increased in it. The yield of potatoes from the introduction of bio-organic fertilizers into the soil increased by 17.4-87.5 %, carrots by 12.8-38.3 %, and beets by 14.0-46.2 %. Bio-organic fertilizers did not adversely affect the quality of potatoes in terms of nitrate content. The level of nitrates in tubers was at the level of 65-215 mg/kg with a MPC of 250 mg/kg. Carrots grown with the use of various bio-organic fertilizers contained 47-136 mg/kg of nitrates at MPC 400 mg/kg, and beet contained 132-429 mg/kg of nitrates at MPC 1400 mg/kg.

The article presents the results of studies on the impact of bioorganic fertilizers on the cultivation of winter wheat, sugar beet, and soybeans in irrigated light sierozems of southeastern Kazakhstan. The study focuses on the effects of these fertilizers on the mineral forms of nitrogen content and the size of N₂O emissions from the soil. When applying leaf treatments of mineral and bioorganic fertilizers to cultivated crops, the nitrogen content in light sierozems is enhanced. The main sources of nutrition are easily hydrolyzable and nitrate nitrogen, which accounts for more than 80 %. The contribution of ammonium forms to plant nutrition is insignificant. The size of nitrous oxide emissions was recorded at the beginning of the experiment and after the initial leaf treatment. Under winter wheat crops, the initial concentration of nitrous oxide was 440.3 µg/m³. In the field prepared for sowing sugar beet and soybean in 2023, the concentrations were 373.7 µg/m³ and 557.7 µg/m³, respectively. After the initial treatment, the vegetation on the leaves showed that, on average, the indicator in the different experimental variants for winter wheat crops was 679 µg/m³, for sugar beet crops was 576.8 µg/m³, and for soybean crops was 637.2 µg/ m³. In agroecosystems, N₂O emissions are higher under winter wheat compared to row crops such as sugar beet and soybean.

The presented mini-review shows a systematic picture of the biological activity of soils in its connection with physical and chemical properties, and, ultimately, with soil fertility and crop yields. The biological activity of soils is due to the lifetime activity of soil biota, mainly microbiota and root systems of plants, as well as the action of soil enzymes. It has been shown that individual BAP tests can be used as simple and accessible biological fertility indices BFI.