Agrobiological Evaluation of Microbiologically Processed Cattle Manure on Soil Properties and Spring Wheat Productivity in Northern Kazakhstan

Abstract

Under rainfed conditions of Northern Kazakhstan, the effects of microbiologically processed cattle manure (CCM) on soil agrochemical and microbiological properties, yield structure, and spring wheat productivity were evaluated over two contrasting growing seasons (2024–2025). Field experiments on chernozem soils tested manure rates of 5–30 t ha⁻¹. Favorable hydrothermal conditions in 2024 enhanced fertilizer efficiency compared with the drier 2025 season. CCM application increased soil nitrate nitrogen from low (<8 mg kg⁻¹) to medium levels (8–12 mg kg⁻¹), while available phosphorus and potassium increased by 15–35% relative to the control across key growth stages. The abundance of major functional microbial groups increased by 1.5–3.0-fold, particularly nitrogen-transforming and cellulose-degrading microorganisms. Grain yield improved significantly in both years, with the highest and most stable yields observed at 15–20 t ha⁻¹, resulting in yield gains of 18–32% compared with the control. Yield improvements were associated with increases in grain number per spike (up to 25–27 grains) and grain weight per spike (up to 1.42–1.62 g). Higher manure rates (20–30 t ha⁻¹) did not confer additional yield benefits. Overall, these findings indicate that moderate CCM application effectively enhances soil fertility, stimulates microbial activity, and improves wheat productivity under dryland conditions.

1. Introduction

Spring wheat (Triticum aestivum L.) is a strategically important crop for Kazakhstan and forms the foundation of grain production in Northern Kazakhstan. It accounts for approximately 70–80% of the country’s total grain output. Kazakhstan consistently ranks among the world’s leading wheat producers and exporters, and the stability of its wheat production is critical for food security both nationally and across Central Asia [1,2,3]. The main wheat-growing areas are located in northern regions characterized by a sharply continental climate, high interannual variability in precipitation, and frequent droughts, all of which significantly constrain crop productivity [4,5]. Under these conditions, enhancing the resilience of wheat agroecosystems and preserving soil fertility are key priorities of regional agricultural science [6].

The soils of Northern Kazakhstan, predominantly Chernozems and dark chestnut soils, historically exhibited high natural fertility. However, prolonged extensive cultivation, the dominance of cereal–fallow rotations, and insufficient application of organic fertilizers have led to declines in agrochemical indicators and a weakening of soil microbiological processes [7,8]. Depletion of soil organic matter has been identified as one of the major factors limiting wheat productivity in arid and semi-arid agroecosystems [9].

At the same time, expansion of livestock production in the region has resulted in increasing volumes of cattle manure, intensifying anthropogenic environmental pressures. Cattle manure is classified as a Class III waste hazard, and inadequate storage or disposal can lead to emissions of toxic gases (NH₃, CH₄, H₂S) as well as contamination of soils and water bodies with nitrogen, phosphorus, and organic compounds [10,11,12]. Nitrogen losses from manure are also considered a significant source of greenhouse gas emissions from agriculture [13]. In addition, livestock waste may contain pathogenic and opportunistic microorganisms, including Salmonella spp., Escherichia coli, and Listeria monocytogenes, posing risks to human and animal health [14,15]. Raw manure may also contain viable weed seeds that remain germinable after passage through the digestive tract, increasing weed infestation, competition for water and nutrients, and ultimately reducing wheat yield—an issue particularly critical under the moisture-limited conditions of Northern Kazakhstan [16,17,18].

Despite these risks, cattle manure represents a valuable source of organic matter and essential plant nutrients—nitrogen, phosphorus, and potassium—whose deficiency is a major limiting factor for wheat productivity in dry-steppe regions [19,20,21]. Numerous studies have demonstrated that organic fertilizers enhance soil organic carbon content, improve soil structure and water retention, and stimulate microbial activity, thereby increasing nutrient availability to plants [22,23,24,25].

Various manure management technologies have been proposed, including combustion, biogas production, gasification, vermicomposting, and biofermentation [26,27]. However, for large-scale agricultural systems, microbiological processing using active microbial strains is of particular practical interest because it reduces pathogenic microflora, lowers pollutant emissions, and produces fertilizers with enhanced nutrient bioavailability [28,29,30]. Microbiologically activated organic fertilizers have been shown to increase soil microbial biomass, enzymatic activity, and functional diversity, which are directly associated with yield improvements in cereal crops, including wheat [31,32]. Several studies have also indicated that organic and biologically activated fertilizers provide more stable wheat yields than exclusively mineral fertilization systems, especially under limited moisture and high climatic variability [33,34].

Nevertheless, despite extensive international research, data on the effects of microbiologically processed cattle manure on soil agrobiological properties and spring wheat productivity under the specific soil–climatic conditions of Northern Kazakhstan remain limited, particularly with respect to interannual weather variability [35]. In addition, the unique microbial consortium used in this study and its impact on functional groups involved in nitrogen transformation, cellulose decomposition, and biological nitrogen fixation have not been previously evaluated in this region.

Therefore, this study provides new insights into how region-specific microbiologically activated manure influences soil nutrient dynamics, microbial activity, and yield structure under contrasting hydrothermal conditions. The objective of this study was to evaluate the agrobiological effects of microbiologically processed cattle manure in wheat cultivation under the conditions of Northern Kazakhstan based on two-year field experiments.

2. Materials and Methods

2.1. Research Conditions

The field experiment to assess the effects of microbiologically processed cattle manure (CCM) was conducted in 2024–2025 in the Akmolinsk region, Shortandy district, at the field of the Scientific Production Center of Grain Farming named after A.I. Baraev (51°36′ N, 70°02′ E). The region is characterized by a sharply continental climate with cold, prolonged winters and moderately warm, short summers during the growing season. Average annual precipitation ranges from 250 to 400 mm, with most rainfall occurring during the warm period. The climate causes significant diurnal and annual temperature fluctuations, with mean annual air temperature ranging from 1.4 °C to 8.8 °C [36].

The soil at the experimental site is a southern Chernozem with a moderately heavy loam texture. The humus content ranges from 3.0–3.2%, total nitrogen from 0.12–0.18% (moderate availability), total phosphorus from 0.12–0.16% (moderate availability), and total potassium from 1.5–2.2% (high availability), reflecting moderate to high fertility. Available soil nutrients were measured as nitrate nitrogen, Olsen phosphorus, and exchangeable potassium to assess nutrient status during the experiment. The humus horizon is approximately 22 cm thick and has a silty structure. Soil reaction is slightly alkaline (pH 7.9–8.3). In the cation exchange complex, calcium (up to 80%) and magnesium (11%) are the dominant cations.

2.2. Study Object and Agronomic Conditions

The object of the study was spring wheat (Triticum aestivum L.), variety Astan-2. Astan-2 is a mid-early variety with a growing period of 83–88 days, developed by Kazakhstani breeders at the Scientific Production Center of Grain Farming named after A.I. Baraev. Plant height ranges from 95 to 120 cm. The variety is highly resistant to lodging and shattering and shows resistance to brown and stem rust, with relatively high resistance to dusty smut. The 1000-grain weight is 31–35 g, specific weight is 787 g/L, protein content is 15.3%, and wet gluten content is 32.8%. It is classified as a high-quality wheat with excellent baking properties [37].

The experiment was established as a randomized complete block design with three replicates and six treatment levels (control and five manure application rates;

Table 1. Experimental design of the spring wheat.

Treatment	Manure Application (t ha−1)
1	O—Control (no manure applied)
2	Cattle manure 5 t ha−1
3	Cattle manure 10 t ha−1
4	Cattle manure 15 t ha−1
5	Cattle manure 20 t ha−1
6	Cattle manure 30 t ha−1

). Each replicate (block) contained all treatments randomly assigned to plots to minimize the effect of spatial variability. The area of each plot was 2 m² (1 × 2 m), with a central harvest area of 1 m² used for yield determination in order to minimize edge effects from adjacent plots (Figure 1). Grain yield was measured by harvesting plants from the central area and converting the results to a hectare basis at a standard grain moisture content of 14%.

The treatments were applied to the same plots in both experimental years (2024–2025), allowing assessment of cumulative and residual effects of microbiologically processed cattle manure.

Wheat was sown at the optimal time for the region (19–20 May) at a seeding rate of 3.5 million viable seeds per hectare. Sowing depth was 4–5 cm with row spacing of 22 cm, using a one-row Rowseed 1R seeder, followed by rolling to ensure uniform emergence through improved seed-to-soil contact.

2.3. Preparation and Application of Microbiologically Processed Cattle Manure

Microbiologically processed cattle manure (CCM) was used in the experimental treatments. The manure was obtained by fermenting the initial organic material—semi-rotted cattle manure with 67% moisture content—using a consortium of effective microorganisms (EM) from Consortium 1. The microbial consortium included the strains Bacillus zanthoxyli 21H and 22H—Gram-positive spore-forming bacteria—and Streptomyces sp. 34H—a Gram-positive filamentous actinobacterium with a well-developed secondary metabolism. The co-presence of Bacillus and Streptomyces ensures functional complementarity of the consortium due to differences in their physiology, metabolic activity, and ecological strategies. Together, these strains enhance the mineralization of organic matter, break down complex polymers, and contribute to the microbiological stabilization of the manure, ensuring an efficient and environmentally friendly decomposition process.

The microorganisms were cultivated in a liquid nutrient medium based on wheat bran [38] at 32 °C, pH 7. The total volume of the consortium was 5 L, with a microbial concentration of 5.36 × 10⁷ CFU mL⁻¹. For application, the consortium was diluted with chlorine-free tap water at room temperature (~20–25 °C) to a final volume of 50 L. The resulting suspension was evenly applied to 10 t of cattle manure to ensure uniform inoculation and effective contact between microorganisms and the organic substrates.

Microbial processing was carried out under aerobic conditions for 30 days. To maintain aerobic conditions, the manure was arranged in layers approximately 10–15 cm thick and periodically mixed (turned) every 3–5 days to ensure adequate oxygen supply and prevent anaerobic zones. This approach facilitated uniform decomposition and active microbial metabolism throughout the composting process.

The microbial strains used in the consortium were isolated from local cattle manure in Kazakhstan during an initial screening of 43 bacterial isolates. These strains were selected based on their biotechnological significance, including their ability to decompose organic matter, fix nitrogen, and produce proteases and catalases. Both Bacillus zanthoxyli and Streptomyces sp. were the most effective isolates in terms of organic matter breakdown and microbiological stability. They have been deposited in the Republican Collection of Microorganisms LLP, Kazakhstan, and are laboratory isolates, not commercially available preparations.

The processed manure was applied one month before sowing, superficially incorporated into the soil to a depth of 15 cm. Before applying the manure to the soil, its agrochemical and microbiological composition was analyzed.

2.4. Agrochemical Analyses

The agrochemical analysis of the manure included the determination of total nitrogen content by the Kjeldahl method (11261:1995) [39]. Available phosphorus was measured by the Olsen method using 0.5 M NaHCO₃ (pH 8.5), followed by spectrophotometric analysis according to ISO 11263:1994 [40]. Exchangeable potassium was determined after extraction with 1 M ammonium acetate (pH 7.0) and subsequent flame photometric measurement (ISO 11260:2011) [41]. Organic matter content was assessed using the Walkley-Black method with dichromate oxidation, based on ISO 14235:1998 [42]. Soil pH was measured potentiometrically in a 1:2.5 soil-to-water slurry using a calibrated glass electrode, according to ISO 10390:2005 [43].

The agrochemical analysis of soil included determination of nitrate nitrogen by potentiometric measurement using a nitrate-selective electrode after extraction with 0.01 M CaCl₂ (ISO 11263, modification for nitrate ions) [44]. Available phosphorus was determined spectrophotometrically after ammonium-lactate extraction (Egner-Riehm method), and available potassium was determined by the same method with subsequent photometric or atomic absorption measurement [45].

All analyses of composted cattle manure and soil samples were performed at the accredited laboratory of the Agroecological Testing Center of the S. Seifullin Kazakh Agro-Technical University.

Soil samples were collected from control and fertilized plots at various wheat growth stages from a depth of 0–20 cm (upper plow layer) using a hand auger. A composite sample was created from five points per plot. Samples were transported in tightly sealed fabric bags, air-dried, ground, and sieved through 1 or 2 mm mesh, depending on the parameter analyzed. For microbiological studies, soil was sampled at the same depth and collected in sterile containers.

2.5. Microbiological Studies

Microbiological soil analyses were performed using selective culture media: starch–ammonium agar (for microorganisms utilizing mineral nitrogen), Ashby’s medium (for free-living nitrogen-fixing bacteria), Gause’s medium (for actinomycetes), meat–peptone agar (for ammonifying bacteria), Czapek–Dox medium (for micromycetes), and Hutchinson’s medium (for cellulose-decomposing microorganisms).

Microbial populations were determined by the serial dilution plating on solid nutrient media, followed by colony counting. Briefly, 1 g of fresh soil was suspended in 9 mL of sterile physiological saline solution (0.85% NaCl) to obtain an initial 10⁻¹ dilution. Subsequent serial tenfold dilutions were prepared, and appropriate aliquots were plated onto the respective media. After incubation under suitable conditions, colonies were counted, and microbial abundance was expressed as colony-forming units per gram of dry soil (CFU g⁻¹).

2.6. Structural Analysis of the Wheat Crop

The structural analysis of the wheat crop was conducted to evaluate the productivity elements that determine yield formation. The analysis was carried out using one plant from each experimental plot at full maturity. For these plants, the following parameters were measured: plant height, total and productive stem number, spike length, number of spikelets per spike, number of grains per spike, grain mass per spike, and 1000-grain weight [46].

The results of the structural analysis were used to identify the effects of the experimental factors on yield formation and to determine the limiting elements of wheat productivity under experimental conditions.

2.7. Statistical Data Processing

All experimental data were subjected to statistical analysis. The mean values and standard deviations were calculated based on three replicates per treatment. To identify significant differences among treatments, a one-way analysis of variance (ANOVA) was performed, followed by the least significant difference (LDS) test at a significance level of p ≤ 0.05. The experiment was conducted as a completely randomized block design with three replicates per treatment.

3. Results

3.1. Meteorological Conditions During the Study Years

Pronounced differences in meteorological conditions were observed during the spring wheat growing seasons of the study years, primarily related to precipitation distribution and temperature regime (

Table 2. Characterization of meteorological conditions during the study years (2024 data from the Shortandy meteorological station; 2025 data from the RP5 meteorological database).

Year of Study	Precipitation (mm)					Average Daily Air Temperature (°C)
	May	June	July	August	V–VIII	May	June	July	August	V–VIII
Long-term averages	32.4	39.5	57.0	39.8	168.7	12.5	18.3	19.9	17.4	17.0
2024	76.9	62.3	63.3	106.6	309.1	11.2	22.6	21.7	17.3	18.2
2025	40	35	10	105	190	16.3	19.7	19.7	17	18.2

).

In 2024, weather conditions during the sowing period were characterized by increased moisture availability. Precipitation totaling 76.9 mm ensured the formation of sufficient productive soil moisture reserves in the post-sowing period, which is atypical for the climatic conditions of Northern Kazakhstan. As shown in Table 2, total precipitation during the 2024 growing season reached 309.1 mm, exceeding the long-term average by 168.7 mm. The majority of precipitation occurred in May (76.9 mm) and August (106.6 mm). Abundant rainfall in August prolonged the growing season and delayed the harvest of spring wheat.

Meteorological conditions during the summer period were highly variable, with sunny and hot days alternating with overcast conditions accompanied by gusty winds and heavy rainfall. The highest daily air temperatures were recorded in June and July, reaching 30–33 °C.

In 2025, precipitation during the growing season was distributed unevenly among months. In May, precipitation slightly exceeded the long-term average, whereas June and July experienced a pronounced moisture deficit, receiving 35 mm and 10 mm of rainfall, respectively. Despite these relatively dry conditions, moisture stress in wheat plants was not pronounced. This can be attributed to sufficient productive soil moisture reserves formed from autumn and spring precipitation, as well as moderate air temperatures during this period, which helped limit heat stress and supported normal physiological activity and productivity of the crop.

August 2025 was unusually wet, with 105 mm of precipitation, exceeding the long-term average (39.8 mm) by 65.2 mm.

Overall, meteorological conditions during the 2025 wheat growing season can be considered relatively favorable for crop growth and development. However, excessive rainfall in August required increased attention to phytosanitary conditions and harvest management.

3.2. Agrochemical and Microbiological Characteristics of Microbiologically Processed Cattle Manure

In the present study, microbiologically processed cattle manure was applied as an organo-mineral fertilizer. Prior to field application, the manure was subjected to comprehensive agrochemical and microbiological analyses to characterize its nutrient composition and the activity of beneficial microbial communities associated with plant growth promotion.

The processed manure was characterized by a high organic matter content, near-neutral pH, and substantial concentrations of essential macronutrients, indicating its suitability as an effective source of both nutrients and organic material for soil amendment. In addition to its chemical composition, microbiological properties are a key determinant of its agronomic efficiency, as they influence organic matter decomposition and nutrient transformation processes.

A consolidated overview of the agrochemical properties and microbiological composition of the processed manure is presented in

Table 3. Agrochemical properties and microbial composition of microbiologically processed cattle manure.

Parameter	Value	Interpretation
Agrochemical properties
Organic matter	25.8%	High organic content
pH	6.9	Near neutral
Nitrogen (N)	2.03%	High
Phosphorus (P)	0.43%	Moderate
Potassium (K)	1.40%	High
Microbial groups
Heterotrophic bacteria (MPA)	1.7 × 107 CFU g−1	Utilize organic N
Mineral-N-utilizing bacteria (SAA)	1.4 × 107 CFU g−1	Mineral N transformers
Actinomycetes (Gause medium)	4.0 × 103 CFU g−1	Decomposers
Actinomycetes (Hutchinson)	2.8 × 103 CFU g−1	Cellulose degradation
Fungi (Hutchinson)	2.0 × 103 CFU g−1	Fungal community
Fungi (Czapek–Dox)	1.0 × 103 CFU g−1	Minor group
Nitrogen-fixing bacteria (Ashby)	3.2 × 107 CFU g−1	Biological N fixation

.

Microbiological analysis revealed a high abundance and diversity of functional microbial groups, confirming the elevated biological activity of the processed manure. The growth of heterotrophic bacteria on meat–peptone agar indicates active utilization of organic nitrogen compounds, whereas microbial development on starch–ammonium agar reflects the presence of populations capable of assimilating mineral nitrogen forms. Actinomycetes identified on Gause and Hutchinson media suggest active involvement in the decomposition of complex organic substrates, including cellulose. The presence of fungi on Hutchinson and Czapek–Dox media indicates their contribution to organic matter transformation and nutrient cycling.

A particularly notable feature is the high abundance of nitrogen-fixing bacteria (3.2 × 10⁷ CFU g⁻¹) detected on Ashby medium. This medium is selective for free-living diazotrophs, primarily Azotobacter spp., indicating that these microorganisms were present in the processed manure and likely contributed to its nitrogen-enriching potential. The presence of such functional groups enhances the capacity of the manure to improve soil nitrogen availability following application.

Overall, the combined agrochemical and microbiological characteristics indicate that microbiologically processed cattle manure possesses high biological activity and strong potential to stimulate organic matter turnover and improve nutrient availability in agricultural soil systems.

3.3. Dynamics of Mineral Nutrient Elements in Soil

Application of microbiologically processed cattle manure exerted a multifaceted influence on soil properties through the combined effects of its agrochemical composition and biological activity. High inputs of organic matter, nitrogen, phosphorus, and potassium, along with an active and diverse microbial community, contributed to improved soil structure, enhanced fertility, and increased nutrient availability for crops. To quantify these effects, key agrochemical soil parameters were determined sequentially at major growth stages of spring wheat under different manure application rates (Figure 2). This approach allowed the assessment of the dose-dependent influence of processed manure on macronutrient dynamics, soil biochemical processes, and crop development throughout the growing season, which is of practical relevance for improving yield stability and productivity in the chernozem soils of Northern Kazakhstan.

Soil nitrate nitrogen availability was evaluated according to the classification proposed by Chernenok for zonal soils of Northern Kazakhstan and cereal crops: <4 mg kg⁻¹—very low; 4–8 mg kg⁻¹—low; 8–12 mg kg⁻¹—medium; and 12–15 mg kg⁻¹—optimal [47].

In 2024, soil nitrate nitrogen content varied markedly depending on manure application rate and wheat growth stage (Figure 2). In the control treatment, N–NO₃⁻ concentrations remained consistently within the low category throughout the vegetation period. Application of manure resulted in a clear dose-dependent increase in nitrate nitrogen. At the optimal rate of 15 t ha⁻¹, soil nitrate nitrogen increased by approximately 35–45% at the seedling stage, 40–55% at flowering, and 45–60% at full maturity compared with the control. Higher application rates (20–30 t ha⁻¹) further increased nitrate levels but did not result in proportionally greater agronomic benefits. A similar pattern was observed in 2025, where nitrate nitrogen increased by 30–50% across growth stages at 15 t ha⁻¹, confirming a stable positive response to manure application under contrasting climatic conditions.

Comparable trends were observed for available phosphorus, which also showed strong dependence on manure application rate and crop developmental stage (Figure 2). Phosphorus availability was interpreted according to Chernenok’s classification for Northern Kazakhstan soils: <10 mg kg⁻¹—very low; 10–15 mg kg⁻¹—low; 15–25 mg kg⁻¹—medium; 25–40 mg kg⁻¹—elevated; and >40 mg kg⁻¹—high [48].

In 2024, phosphorus content under the optimal treatment (15 t ha⁻¹) increased by approximately 10–15% at the seedling stage, 12–18% at flowering, and 10–20% at full maturity relative to the control. In 2025, the increase was slightly more pronounced, reaching 15–25% across growth stages, with even the lowest manure rate shifting soil phosphorus from low to medium levels. Increasing manure doses resulted in gradual phosphorus enrichment; however, differences between 15 and 30 t ha⁻¹ were relatively small, indicating diminishing returns.

Exchangeable potassium also showed a consistent positive response to manure application. At 15 t ha⁻¹, potassium content increased by approximately 5–8% at the seedling stage, 6–10% at flowering, and 5–9% at full maturity compared with the control in 2024, while in 2025 increases ranged from 6–12% across growth stages. The highest potassium values were observed in plots receiving 30 t ha⁻¹; however, similar to nitrogen and phosphorus, the incremental gains above 15–20 t ha⁻¹ were relatively small. Overall, these results indicate that moderate manure application rates (15–20 t ha⁻¹) are sufficient to substantially improve soil nutrient status without excessive input.

3.4. Soil Microbiological Status

A comprehensive evaluation of the effectiveness of microbiologically processed cattle manure (CMM) requires consideration of soil microbiological status, which plays a key role in organic matter mineralization, nutrient availability, and plant health. The composition and abundance of major functional groups of soil microorganisms were assessed at different wheat growth stages to identify relationships between biological activity and nutrient dynamics (Figure 3 and Figure 4). Microbial counts were log₁₀-transformed prior to statistical analysis to meet ANOVA assumptions of normality and homogeneity of variances.

3.4.1. Starch–Ammonium Agar (SAA)

Microorganisms involved in mineral nitrogen assimilation and ammonification varied with growth stage, manure rate, and year. In 2024, populations at 15 t ha⁻¹ were 1.5–2.0 times higher than CK at seedling, 1.6–2.1 times at flowering, and 1.7–2.3 times at full maturity. Application of 20–30 t ha⁻¹ produced similar or slightly higher abundance (Figure 3A). In 2025, microbial counts at 15 t ha⁻¹ were ~1.4–1.6 fold higher than control across growth stages, and 20–30 t ha⁻¹ maintained elevated populations through full maturity (Figure 4A).

3.4.2. Meat-Peptone Agar (MPA)

Microbes utilizing organic nitrogen peaked at flowering. In 2024, counts at 20 t ha⁻¹ were ~1.7–2.0× higher than CK, while at full maturity, 15 t ha⁻¹ showed 1.5× higher abundance (Figure 3B). In 2025, populations at 15–30 t ha⁻¹ exceeded CK by ~1.3–1.6×, demonstrating sustained microbial stimulation (Figure 4B).

3.4.3. Gause Medium

Actinomycete abundance varied substantially across growth stages and manure application rates. At seedling stage in 2024, 30 t ha⁻¹ showed 2.2× higher abundance than CK, while at full maturity, 5 t ha⁻¹ had 1.8× higher counts (Figure 3C). In 2025, 30 t ha⁻¹ increased counts by ~2.0–3.3× compared with CK at flowering and full maturity, although overall abundance remained lower than in 2024 (Figure 4C).

3.4.4. Hutchinson Medium

Cellulose-decomposing microorganisms exhibited distinct seasonal patterns. Peak abundance occurred during flowering in 2024, exceeding CK by 2.5–3.0×. By full maturity, 15–30 t ha⁻¹ increased counts by ~1.8–2.0× relative to control (Figure 3D). In 2025, full-maturity populations at 15–30 t ha⁻¹ were ~3.0× higher than CK (Figure 4D).

3.4.5. Ashby Medium

Cellulose-decomposing microorganisms exhibited distinct seasonal patterns. In 2024, flowering-stage populations at 15–30 t ha⁻¹ exceeded CK by 2.0–3.0×, while at full maturity 15 t ha⁻¹ showed 1.8× higher counts (Figure 3E). In 2025, 15–30 t ha⁻¹ resulted in ~2.0–2.5× greater abundance than control (Figure 4E).

3.4.6. Czapek–Dox Medium

Micromycete abundance was higher in 2024 than in 2025, indicating more favorable conditions for organic matter mineralization. In 2024, moderate manure rates (15–20 t ha⁻¹) increased fungal abundance by ~1.5–2.0× compared with CK, whereas in 2025 only higher rates (20–30 t ha⁻¹) resulted in moderate increases (~1.3–1.6×), reflecting constrained fungal activity under less favorable conditions (Figure 3F and Figure 4F).

Although higher manure application rates generally stimulated microbial abundance, the absence of proportional increases—and in some cases reduced responses at 30 t ha⁻¹—suggests the presence of limiting ecological factors. This may be attributed to temporary immobilization of nutrients within microbial biomass, leading to increased competition between microbial groups and plants for available nitrogen. In addition, excessive organic inputs can alter the C:N balance and oxygen availability, creating less favorable conditions for certain microbial populations, particularly under moisture-limited environments. Such effects indicate that moderate manure rates provide a more balanced substrate supply, supporting stable microbial activity without inducing competitive or environmental stress.

Overall, manure application strongly stimulated the abundance and activity of functional microbial groups. The magnitude and temporal pattern of responses depended on manure rate, wheat growth stage, and environmental conditions. Moderate rates (10–20 t ha⁻¹) produced the most stable and pronounced microbial activity, whereas very high doses sometimes reduced responses or shifted peak activity across stages. These patterns suggest that excessively high manure rates (e.g., 30 t ha⁻¹) may reduce microbial response due to substrate limitation, increased competition among microbial groups, or environmental stress such as oxygen limitation, confirming that moderate manure rates provide a more balanced and favorable environment for microbial activity. These results confirm the key role of microbiologically processed manure in regulating soil microbial processes and nutrient cycling in wheat agroecosystems.

3.5. Yield Structure Formation

The results indicate that application of microbiologically processed cattle manure exerted a complex influence on soil agrochemical and microbiological properties at different stages of wheat development. The conditions, together with interannual variability in weather patterns, determined specific features of crop growth, development, and productivity. Therefore, further analysis focused on yield structure components as integrated indicators of the effectiveness of the tested agrobiological practice (

Table 4. Yield structure of spring wheat under different application rates of microbiologically processed cattle manure in 2024–2025.

Treatment	Stems per Plant	Productive Stems	Plant Height (cm)	Spike Length (cm)	Spikelets (No.)	Grains per Spike (No.)	Grain Weight per Spike (g)	1000-Grain Weight (g)
2024
Control	2.2 ± 0.2c	2.2 ± 0.2b	79 ± 0.6c	5.9 ± 0.3c	11.2 ± 0.4c	21 ± 0.6d	0.92 ± 0.1c	32.6 ± 0.4c
Manure 5 t ha−1	2.3 ± 0.2bc	2.2 ± 0.3b	81 ± 0.6b	6.4 ± 0.2c	11.8 ± 0.2c	22 ± 0.6c	1.38 ± 0.0b	34.2 ± 0.8b
Manure 10 t ha−1	2.5 ± 0.2b	2.3 ± 0.3b	82 ± 0.6b	7.0 ± 0.3b	12.1 ± 0.4c	23 ± 0.6c	1.35 ± 0.0b	34.8 ± 0.9b
Manure 15 t ha−1	2.7 ± 0.3ab	2.5 ± 0.4ab	89 ± 0.6a	7.2 ± 0.3b	12.8 ± 0.6b	25 ± 0.6b	1.42 ± 0.0b	37.7 ± 0.5a
Manure 20 t ha−1	2.6 ± 0.2ab	2.6 ± 0.2ab	87 ± 0.6ab	7.4 ± 0.5b	13.1 ± 0.4b	27 ± 0.6a	1.51 ± 0.0ab	35.0 ± 0.3b
Manure 30 t ha−1	2.9 ± 0.5a	2.7 ± 0.3a	88 ± 0.6a	9.3 ± 0.3a	15.2 ± 0.2a	27 ± 0.6a	1.62 ± 0.1a	34.0 ± 1.0b
LSD0.05	0.46	0.44	2.05	0.73	0.89	1.42	0.27	1.63
2025
Control	1.8 ± 0.4a	1.7 ± 0.4a	75.1 ± 0.3b	7.2 ± 0.6b	12.2 ± 0.2b	23 ± 0.6b	0.97 ± 0.1c	25.2 ± 0.3c
Manure 5 t ha−1	2.2 ± 0.2a	2.1 ± 0.1a	75.3 ± 0.7b	7.2 ± 0.4b	12.6 ± 0.2ab	23 ± 0.6b	1.34 ± 0.1b	26.0 ± 0.5c
Manure 10 t ha−1	1.9 ± 0.2a	1.8 ± 0.2a	76 ± 1.0ab	7.3 ± 0.2b	12.7 ± 0.7a	24 ± 0.6b	1.43 ± 0.1ab	27.5 ± 0.9b
Manure 15 t ha−1	1.7 ± 0.1a	1.7 ± 0.1a	76.7 ± 0.8a	7.4 ± 0.7ab	12.6 ± 0.8ab	25 ± 1.0b	1.54 ± 0.9a	27.9 ± 0.4ab
Manure 20 t ha−1	1.9 ± 0.2a	1.9 ± 0.2a	77 ± 0.5a	7.5 ± 0.6ab	12.8 ± 0.8a	26 ± 1.0ab	1.57 ± 0.8a	28.9 ± 0.8a
Manure 30 t ha−1	1.8 ± 0.2a	1.8 ± 0.2a	77 ± 1.0a	7.7 ± 0.3a	13.0 ± 0.2a	28 ± 0.6a	1.62 ± 0.0a	28.8 ± 0.8a
LSD0.05	0.71	0.43	1.39	0.62	0.86	1.94	0.75	1.22

Footnote: Values represent means ± SD (n = 3); (a–c) different lowercase letters within the same column indicate significant differences among treatments at p < 0.05. Microbial counts used log₁₀-transformed values for ANOVA; yield traits analyzed using raw values.

).

Application of manure enhanced plant productivity through targeted modifications of individual yield-structure components. In 2024, yield improvement was primarily associated with increases in the number of productive stems (up to 2.5–2.7 at 15–20 t ha⁻¹, representing 14–23% increase compared with 2.2 in the control), spike length (up to 7.2–7.4 cm, 22–25% increase compared with 5.9 cm), number of spikelets per spike (up to 12.8–13.1, 24–27% increase vs. 10.3 in CK), and number of grains per spike (up to 25–27, 25–32% increase vs. 20.4). A substantial contribution to yield formation was also provided by increased grain weight per spike, which reached 1.42–1.62 g at application rates of 15–30 t ha⁻¹ (22–45% increase vs. 1.17 g in CK). In addition, higher 1000-grain weight values (35.0–37.7 g) indicated more intensive grain filling under favorable moisture conditions (16–27% increase vs. 30.1 g in CK).

The most balanced improvement in yield structure was observed at manure application rates of 15 and 20 t ha⁻¹, where yield enhancement resulted from simultaneous increases in both quantitative traits (productive stems and grain number per spike) and qualitative parameters (grain weight per spike and 1000-grain weight). Increasing the application rate to 30 t ha⁻¹ led to further enlargement of certain morphological traits, particularly spike length (up to 9.3 cm, 58% increase vs. CK) and spikelet number (up to 15.2, 47% increase vs. CK); however, these changes were not accompanied by proportional increases in grain mass, suggesting reduced efficiency of excessive organic fertilization.

In 2025, the positive effect of manure application on yield structure was maintained; however, yield formation was driven predominantly by improvements in generative traits. At application rates of 20–30 t ha⁻¹, grain weight per spike increased to 1.57–1.62 g (18–25% increase vs. 1.33 g in CK) and 1000-grain weight to 28.8–28.9 g (16–17% increase vs. 24.8 g in CK), whereas changes in tillering intensity and plant height were relatively limited. This indicates that under less favorable weather conditions, yield formation was governed mainly by grain-filling processes rather than by increases in the number of productive organs.

3.6. Effect of Microbiologically Processed Cattle Manure on Spring Wheat Yield

The results demonstrated that the application of microbiologically processed cattle manure significantly increased the grain yield of spring wheat. The observed yield enhancement was associated with a more complete realization of yield-structure components, confirming the positive role of this organic fertilizer in promoting grain production under the rainfed conditions of Northern Kazakhstan (Figure 5).

Under these dryland conditions, manure application positively affected wheat yield in both study years; however, the magnitude of the response depended on application rate and meteorological conditions during the growing season. In 2024, characterized by more favorable moisture availability, all manure treatments resulted in significantly higher grain yields compared with the control (Figure 5A). The highest productivity was achieved at an application rate of 15 t ha⁻¹, which produced the greatest yield increase (Figure 5B). Further increases in manure rate did not lead to additional yield gains, indicating a plateau in the yield response.

In 2025, which was marked by less favorable moisture conditions, overall wheat productivity declined; nevertheless, the beneficial effect of microbiologically processed cattle manure remained evident. The strongest yield response was again observed at 15 t ha⁻¹, where yield increases above the control were substantially greater than those at both lower and higher application rates (Figure 5B). Lower manure rates resulted in only moderate yield improvements, whereas higher rates did not compensate for the negative effects of environmental stress.

3.7. Relationship Between Manure Application Rate and Productivity

To clarify the relationship between manure application rate and wheat productivity, regression analysis was performed to describe yield responses to different application rates of microbiologically processed cattle manure (Figure 6). Manure dose was treated as a continuous variable, and a quadratic regression model was applied. The regression coefficients were tested for statistical significance (p < 0.05) using a standard statistical package, and the optimal manure application rate was determined analytically from the first derivative of the quadratic equation.

Analysis of yield responses in Northern Kazakhstan during 2024–2025 revealed a pronounced dose–response relationship with a distinct optimum. In 2024, grain yield increased with increasing manure rate and reached a maximum within the range of tested doses. This relationship was described by the following quadratic regression model:

y = −0.0129x² + 0.5306x + 19.091, R² = 0.953,

(1)

The high coefficient of determination indicates that approximately 95% of the variation in grain yield was explained by manure application rate, highlighting the dominant role of fertilization under favorable environmental conditions. Analytical determination of the maximum based on the first derivative (x = b/2a) indicates an optimal manure rate of approximately 20–21 t ha⁻¹.

In 2025, which was characterized by less favorable weather conditions, grain yield responses also followed a quadratic trend, although absolute yield level were lower:

y = −0.0098x² + 0.3771x + 13.423, R² = 0.723

(2)

This model indicates that approximately 72% of the variation in grain yield was explained by manure rate. The calculation optimum for 2025 was approximately 17–18 t ha reflecting a shift toward lower optimal input levels under moisture-limited conditions.

Despite these differences, both models indicate that the agronomically optimal manure rate lies within the range of 15–20 t ha⁻¹, which is consistent with the experimental results showing that yield gains plateau beyond moderate application rates.

Overall, the regression analysis demonstrates that microbiologically processed cattle manure applied within this range represents the most effective strategy for maximizing spring wheat grain yield under the soil and climatic conditions of Northern Kazakhstan.

4. Discussion

4.1. Role of Climatic Factors in the Realization of Organic Fertilizer Effects

The results of this study demonstrate that the agronomic effectiveness of microbiologically processed cattle manure under rainfed conditions in Northern Kazakhstan is determined not only by its agrochemical composition, but also by the interaction between fertilizer inputs and prevailing climatic conditions, particularly soil moisture and temperature regime during the growing season. Similar climate-dependent responses to organic fertilization have been widely reported for cereal crops grown in arid and semi-arid regions, where water availability is a primary regulator of nutrient release and crop uptake [49,50].

Comparison of the two experimental years revealed that the higher grain yield observed in 2024 was associated less with differences in absolute nutrient supply and more with favorable combination of increased precipitation and moderate temperatures during critical organogenesis stages. Adequate soil moisture is known to enhance organic fertilizers by stimulating microbial activity, accelerating organic matter mineralization, and synchronizing nutrient release with crop demand [51,52]. These mechanisms are consistent with the elevated soil nitrate nitrogen, available phosphorus, and exchangeable potassium contents recorded in 2024, alongside enhanced activity across functional microbial groups.

In contrast, under the drier conditions of 2025, the positive effects of microbiologically processed manure on soil nutrient availability and crop productivity persisted but were constrained by climatic limitations. This aligns with the concept of climate-dependent variability in crop responses to organic fertilization, where the potential benefits of organic inputs are only partially realized under seasonal water deficits [53]. Uneven precipitation distribution and moisture shortages during June and July restricted nutrient uptake and reduced yield formation despite sufficient soil nutrient supply.

Weather analysis further highlighted substantial interannual differences in soil water dynamics. Higher moisture availability in 2024, resulting from abundant autumn–winter and spring precipitation, contributed to the formation of significant reserves of plant-available soil water at the beginning of the growing season. Soil moisture is a key factor controlling both the mineralization rate of organic fertilizers and nutrient mobility [54,55]. Under such conditions, microbiologically processed manure improved soil nutrient status, enhanced microbial activity, and increased grain yield. Conversely, in 2025, although total precipitation approximated long-term averages, its uneven temporal distribution limited the effective utilization of organic fertilizer inputs. Similar patterns have been observed in steppe agroecosystems of Kazakhstan and neighboring regions, where moisture deficits during critical growth stages, such as tillering and grain filling, reduce the efficiency of organic fertilizers [56]. These findings underscore that, in rainfed farming systems, climatic factors—particularly water availability—play a decisive role in determining the extent to which the benefits of organic fertilization can be realized.

4.2. Influence of Manure Application on the Soil Agrochemical Regime

Changes in soil agrochemical indicators clearly confirm the positive effect of microbiologically processed cattle manure on soil nutrient status. The increased concentrations of available nitrogen, phosphorus, and potassium observed at application rates of 15–20 t ha⁻¹ reflect a gradual and sustained release of nutrients during microbial decomposition of organic matter. Similar effects have been reported for processed organic fertilizers, which are characterized by more uniform and prolonged nutrient availability compared with readily soluble mineral fertilizers [57,58]. This controlled nutrient release is particularly important under rainfed conditions, where synchronization between nutrient supply and plant demand determines fertilizer efficiency.

The absence of significant changes in soil solution pH throughout the growing season indicates the environmental safety of the applied manure and its compatibility with the chernozem soils of Northern Kazakhstan. This stability suggests that microbiologically processed manure does not induce soil acidification or alkalization, representing a key advantage over certain mineral fertilizer systems and supporting its suitability for long-term application.

Agrochemical improvements were closely associated with enhanced soil biological activity. The observed increases in bacterial and actinomycete populations in manure-treated plots, particularly at application rates of 10–20 t ha⁻¹, indicate intensified mineralization processes and active nutrient transformation. These microbial groups are known to play a central role in the decomposition of organic substrates and in the conversion of organically bound nutrients into plant-available forms, especially nitrogen and phosphorus [59,60]. The concurrent increases in soil nutrient availability and microbial abundance observed in this study support a strong functional linkage between biological activity and agrochemical regulation.

The dynamics of nitrate nitrogen, available phosphorus, and exchangeable potassium further indicate that microbiologically processed manure functions not only as a direct nutrient source but also as a regulator of nutrient transformation, retention, and temporal availability in soil. Previous studies have shown that organic fertilizers enriched with active microbial consortia can stabilize soil nitrogen dynamics, reduce nutrient losses through leaching or volatilization, and ensure a prolonged nutrient supply to crops [61]. The present findings corroborate these observations and demonstrate that microbiologically processed cattle manure contributes to the development of a more stable and resilient agrochemical environment throughout the growing season, particularly under variable climatic conditions.

4.3. Soil Microbial Activity and Biogeochemical Processes

Analysis of soil microbiological status demonstrated that the application of microbiologically processed cattle manure exerted a pronounced stimulatory effect on major functional groups of soil microorganisms involved in ammonification, organic matter mineralization, cellulose decomposition, and biological nitrogen fixation. These responses are consistent with previous studies showing that organic fertilizers enriched with readily decomposable carbon and active microflora create favorable conditions for microbial growth and intensification of biogeochemical cycling in agricultural soils [62]. In the present study, this stimulation was most evident at moderate manure application rates, which promoted microbial activity without inducing excessive competition for nutrients.

The microbial activity depended on wheat growth stage and interannual environmental conditions, further confirming the close functional relationship between plant development, root exudation patterns, and soil microbial community dynamics. Root-derived carbon inputs regulate microbial metabolism and nutrient transformation processes, while climatic factors—particularly soil moisture and temperature—modulate the magnitude and timing of microbial responses [63]. These interactions possibly explain the pronounced seasonal variability of microbial populations observed across growth stages and between the contrasting weather conditions of 2024 and 2025.

The relatively low abundance of soil fungi observed in this experiment is likely related to the alkaline soil reaction and the regional climatic characteristics of Northern Kazakhstan. Similar patterns have been reported for chernozem and chestnut soils of steppe zones, where bacterial and actinomycete communities typically dominate organic matter decomposition, while fungal activity remains comparatively constrained [64]. This microbial structure favors rapid mineralization of organic substrates and contributes to the observed increases in plant-available nitrogen and phosphorus under manure application.

In comparison with other fertilization systems, the microbial response to microbiologically processed manure appears both quantitatively and functionally distinct. For example, Rusyn et al. (2021) demonstrated that encapsulated mineral fertilizers can stimulate microbial growth and slightly alter soil pH, but the response is often limited to short-term nutrient-driven proliferation [65]. In contrast, the microbiologically activated manure in the present study supported sustained increases in multiple functional groups, suggesting a broader and more persistent enhancement of soil microbial activity and biogeochemical cycling. This indicates that the organic microbial consortium not only supplies nutrients but also actively regulates microbial dynamics, promoting a more resilient soil ecosystem.

Similar observations have been reported in semi-arid cereal systems, where organic manure application enhanced soil microbial biomass, particularly nitrogen-transforming and cellulose-decomposing groups, and improved wheat yield under water-limited conditions [20,33]. These studies support the notion that organic amendments not only supply nutrients but also create favorable ecological conditions for sustained microbial activity, which is essential for synchronizing nutrient availability with crop demand.

The observed shifts in microbial activity were closely linked to changes in yield structure and productivity formation. Under favorable moisture conditions, such as those prevailing in 2024, enhanced microbial mineralization supported increased nutrient availability during early and mid-season growth stages, resulting in a higher number of productive organs. In contrast, under less favorable conditions in 2025, microbial activity contributed primarily to sustaining nutrient supply during the grain-filling period, making assimilate accumulation and grain mass the dominant determinants of yield. These findings underscore the role of soil microbiota as a key mediator linking organic fertilizer inputs, environmental conditions, and crop productivity through the regulation of biogeochemical processes.

4.4. Formation of Yield Structure and Crop Productivity

The observed changes in soil agrochemical properties and microbiological activity were directly reflected in the formation of yield structure and final crop productivity, as soil carbon dynamics and microbial processes play a key role in regulating nutrient availability and plant growth [66]. For spring wheat, the greatest yield increase was consistently obtained at manure application rates of 15–20 t ha⁻¹, which provided optimal conditions for both vegetative development and grain formation. Differences in crop response among treatments can be attributed to the biological characteristics of wheat, including rooting depth and the requirement for synchronized nutrient supply during critical growth stages.

The absence of further yield increases at the highest manure rate (30 t ha⁻¹) indicates that an optimal nutrient threshold had been reached and is consistent with the principle of diminishing returns commonly reported for organic fertilizers [20]. Similar non-linear yield responses have been documented in cereal crops and are generally associated with reduced fertilizer-use efficiency at excessive application rates [67]. Under such conditions, a portion of nutrients may become temporarily immobilized in organic or microbial biomass pools, while intensified microbial activity may increase competition between microorganisms and plants for mineral nitrogen [66].

A particularly important finding of this study is the consistent identification of 15–20 t ha⁻¹ as the optimal manure application rate in both experimental years, despite contrasting climatic conditions. This stability suggests that microbiologically processed cattle manure provides a balanced nutrient supply at moderate rates, enabling efficient realization of yield potential without inducing negative effects associated with over-application. The observed yield structure responses further indicate that under favorable moisture conditions, productivity gains are primarily driven by increases in the number of productive organs, whereas under less favorable conditions, yield formation depends mainly on grain filling and assimilate accumulation [68].

4.5. Relationships Between Soil Nutrients, Microbial Activity, and Yield Formation

The results of this study demonstrate a strong functional linkage between soil nutrient availability, microbial activity, and the formation of yield structure in spring wheat. Increases in nitrate nitrogen, available phosphorus, and exchangeable potassium under manure application were consistently accompanied by stimulation of key functional microbial groups, indicating intensified mineralization and nutrient turnover processes. Such interactions between soil biochemical properties and microbial dynamics are widely recognized as critical drivers of crop productivity in agroecosystems [22,31].

This relationship was most pronounced at the optimal manure application rate of 15–20 t ha⁻¹, where a balanced nutrient supply coincided with high microbial activity. Under these conditions, improved nitrogen availability supported vegetative growth and tillering, while phosphorus and potassium contributed to root development and grain formation. At the same time, increased microbial activity ensured a more synchronized release of nutrients, reducing temporal mismatches between nutrient availability and crop demand [20,68].

The combined effects of enhanced agrochemical and biological soil properties were directly reflected in yield structure components. Under favorable moisture conditions in 2024, increased microbial activity and nutrient availability promoted the formation of a greater number of productive stems and grains per spike. In contrast, under drier conditions in 2025, these factors primarily contributed to improved grain filling and increased grain weight, indicating a shift in the dominant yield-forming processes. Similar climate-dependent interactions between soil biology and crop productivity have been reported in dryland cereal systems [8,33].

The close coupling between microbial activity and nutrient availability under moderate manure application is consistent with reports from semi-arid regions, where balanced organic inputs optimized both soil biological functioning and wheat productivity [20,33]. Our findings reinforce the principle that microbiologically activated manure can improve both yield quantity and quality by regulating nutrient turnover and microbial-mediated soil processes.

Overall, the findings confirm that soil microorganisms act as a key mediator linking organic fertilizer inputs with nutrient dynamics and crop productivity. The close coupling between microbial activity and nutrient availability under microbiologically processed manure application explains the observed improvements in yield structure and supports the concept of integrated agrobiological regulation of crop production.

4.6. Practical Implications and Agroecological Aspects

The higher microbial activity observed in 2024 compared with 2025 highlights the decisive role of hydrothermal conditions in realizing the biological and agronomic potential of organic fertilizers. Numerous studies have shown that under moisture-deficit conditions, even soils with adequate organic matter content may exhibit suppressed microbial activity, resulting in reduced mineralization rates and limited nutrient availability for crops [54,55]. This mechanism explains the more moderate effect of manure on wheat productivity observed in 2025 and underscores the importance of climatic factors in determining fertilizer efficiency [53].

From a practical perspective, these results emphasize the need to integrate weather conditions into fertilizer management strategies for rainfed systems. The consistent effectiveness of microbiologically processed cattle manure at moderate application rates indicates that excessive organic inputs are neither economically justified nor environmentally advantageous under steppe conditions [20]. Instead, management strategies should focus on optimized application rates that balance nutrient supply, microbial activity, and crop demand under variable climatic scenarios.

Overall, the findings align with current concepts of the multifactorial nature of organic fertilizer efficiency and confirm that microbiologically processed cattle manure is an effective component of sustainable farming systems in Northern Kazakhstan. Its application improves soil agrochemical and biological properties, enhances nutrient cycling, and contributes to greater stability of spring wheat production under interannual climatic variability [69]. Identification of an optimal application rate further highlights the importance of adaptive, soil- and climate-specific fertilizer strategies aimed at improving productivity while minimizing environmental risks.

5. Conclusions

Application of microbiologically processed cattle manure increased soil nitrate nitrogen by 30–60%, available phosphorus and potassium by 10–25% relative to the control, stimulated major functional microbial groups by 1.5–3.0-fold, and improved spring wheat grain yield by 18–32% under rainfed conditions of Northern Kazakhstan. Manure application increased the availability of nitrogen, phosphorus, and potassium, stimulated key functional groups of soil microorganisms, and promoted the formation of a favorable yield structure. Across contrasting weather conditions, an optimal application rate of 15–20 t ha⁻¹ was consistently identified, ensuring efficient realization of yield potential without adverse effects associated with excessive organic inputs. These findings indicate that microbiologically activated organic fertilizers can improve wheat productivity and may contribute to stabilizing yields under contrasting seasonal moisture conditions. Further research should focus on long-term field assessments of manure effects on soil fertility and carbon dynamics, as well as on the development of adaptive application strategies tailored to specific soil–climatic conditions and crop requirements.