Soil fertility status and nutrient availability in predominant soils of northern Telangana zone

Introduction

Soil is the basic resource for agricultural production, and its nutrient status has a major influence on crop growth, yield and soil sustainability. Soil survey is a systematic study of soils in a particular area to understand their physico-chemical and chemical properties and their spatial distribution. It includes the assessment of properties such as soil texture, pH, electrical conductivity, organic carbon and the availability of essential nutrients such as nitrogen, phosphorus, potassium and micronutrients. Soil survey help to identify variations in soil fertility from one location to another. The information obtained from soil survey is useful for assessing nutrient deficiencies and determining the fertility status of different areas. It also provides a scientific basis for making suitable fertilizer recommendations and adopting appropriate soil management practices. Thus, soil survey serves as an important link between soil status and agricultural management, helping to improve crop productivity, reduce unnecessary fertilizer use and maintain soil fertility over the long term.

Materials and Methods

Site description

The study was conducted in the Northern Part of Telangana comprising 10 districts. The zone extends geographically between 18°00′ N and 19°30′ N latitudes and 77°00′ E to 80°30′ E longitudes. It receives an average annual rainfall of about 1033 mm ranging between 867 mm and 1189 mm and mean maximum temperature ranging from 33.1 to 33.9 °C and mean minimum temperature ranging from 20.1 to 20.9 °C.

Soil sampling and processes

Total of 120 soil samples (0-15 cm) were selected from the zone. The samples were collected by randomised stratified sampling method from 5-6 places in each site selected for sampling. The soils collected were composited and 2 mm sieved and analysed for physico-chemical and chemical parameters.

Soil analytical methods

Soil pH was determined at 1:2.5 soil water suspension by Glass electrode pH meter (Jackson, 1973) [8] . Soil reaction through EC meter (Jackson, 1973) [8] . Organic carbon by Wet digestion method (Walkley and Black, 1934) [22] . Available N was determined by Permanganate Oxidation distillation method (Subbiah and Asija, 1956) [21] . Available P determined by Olsen et al. (1954) [11] method. Available K was determined by flame photometer (Jackson, 1973) [8] . Available sulphur is determined by CaCl 2 extraction (Williams and steinbergs., 1959) [23] and Turbidity development by Chesnin and Yien (1950) [3] method. Micronutrients are estimated by DTPA extracting solution (Lindsay and Norvell, 1978) [25] .

Statistical analysis

Descriptive statistics was conducted for survey samples and pearson correlation was done to evaluate the interrelation among soil nutrient status.

Results and Discussion

Physical and physico-chemical parameters

Most of the soils in the study area were alkaline (>7.5) in nature contributing to about 70.8%, whereas neutral (6.5-7.5) soils contributed to about 29.2%. Acidic soils (<6.5) were not found over the collected area. The pH of soils were ranged from 6.92 to 8.46. The predominance of alkaline soils were similar with findings of Dandu et al (2025) [4] . The predominance of alkaline conditions over the vast area lead to fixation of phosphorus and other nutrients. The electrical conductivity (EC) (dS m -1 ) of the soils ranged from 0.26 to 2.36 dS m -1 with the mean value of 1.17 dS m⁻¹. 99.16% of soils were non saline (<2.00) in nature and whereas 0.84% were slightly saline (2.00-4.00). The current research findings were comparable with Yilmaz and Algoz (2010) [24] . OC (g kg -1 ) of soils ranged from 1.00-9.28. The soils were mostly less in organic content. 55.8% of soils were low (<5.00) in Organic Carbon whereas 30.8% of samples collected were found in medium (5.0-7.5) OC content 30.8% and 13.3% soils fell under high (>7.5) category. The dominance of low to medium category were in similar to the findings of Diwakar et al. (2021) [5] Available N, P, K (kg ha -1 ) and S (mg kg -1 ) Available Nitrogen in soils ranged from 101 to 277 kg ha -1 with a mean value of 174.68 kg ha -1 . All the samples fell into low category level according to rating of Subbiah and Asija (1956) [21] . The uniformly low category level corroborates with the findings of Katkar et al. (2017) [9] and Dandu et al. (2025) [4] . The available phosphorus content of the soils ranged from 6.5 to 38.3 kg ha⁻¹ with a mean value of 18.35 kg ha⁻¹. Based on the standard rating, 34.2% of the samples were low (< 11 kg ha⁻¹), 40.8% were medium (11-26 kg ha⁻¹) and 25.0% were high (> 26 kg ha⁻¹) in available phosphorus status. The predominance of medium and high available phosphorus status making together of about 65.8% observed in this study is consistent with the findings of Harit and Dhalwani (2025) [7] in Neemuch district and Hadole et al. (2024) [6] in Satara district. Available potassium content ranged from 114 to 428 kg ha⁻¹ with a mean value of 245.63 kg ha⁻¹. The unjudicious use of P fertilisers may lead to P build up in soil. Only 0.8% (one sample) of the soils were low, 66.7% were medium (120-280 kg ha⁻¹) and 32.5% were high (> 280 kg ha⁻¹) in available potassium status. The predominance of K-rich and feldspar minerals in parent material lead to higher K content in soils (Srikant et al., 2008) [20] . The dominance of medium to high potassium status were similar in findings with Prasad et al. (2022) [13] and Singh et al. (2019) [19] . Available sulphur content of the soils ranged from 5.36 to 61.66 mg kg⁻¹ with a mean value of 31.95 mg kg⁻¹. The majority of the samples, 89.2%, were high in available sulphur status (> 15 mg kg⁻¹), while 5.8% were medium (10-15 mg kg⁻¹) and 5.0% were low (< 10 mg kg⁻¹). The results were similar to the findings of Satish et al (2018) [17] .

Micronutrients (Zn, Cu, Fe and Mn)

Available zinc content ranged from 0.16 to 2.36 mg kg⁻¹ with a mean value of 0.80 mg kg⁻¹. Nearly half of the soils, 49.2%, were deficient in zinc (< 0.6 mg kg⁻¹), while 50.8% were sufficient. Available copper content ranged from 0.29 to 5.36 mg kg⁻¹ with a mean value of 1.50 mg kg⁻¹. All the samples (100%) were found to be sufficient (> 0.2 mg kg⁻¹) in available copper. Available iron ranged from 2.18 to 21.63 mg kg⁻¹ with a mean value of 11.06 mg kg⁻¹. 99.2% of the samples were sufficient (> 2.5 mg kg⁻¹) in iron, with only one sample (0.8%) recording a deficient status. Available manganese ranged from 3.12 to 25.36 mg kg⁻¹ with a mean value of 11.25 mg kg⁻¹. All the samples (100%) were sufficient (> 2.0 mg kg⁻¹) in manganese status. The nearuniversal sufficiency of Cu, Fe and Mn together with widespread zinc deficiency recorded in this study closely parallels to the the observations of Reddy et al. (2014) [16] , Prasad et al. (2020) [13] and Shukla et al. (2021) [18] .

Correlation among soil properties

Pearson correlation analysis was performed on the 120 surface-soil observations (0-15 cm) to evaluate the interrelation among soil nutrient status. The correlation matrix was developed using the soil parameters viz., pH, EC, organic carbon (OC), available N, P, K, S, Zn, Fe, Cu and Mn. Correlation among the OC, N and K contents were similar to the findings Adhikari et al. (2015) [1] . The negative correlation of P-Zn content were similar to the findings of Mondal et al. (2017) [10] . The highest correlated value (r = 0.620) was among pH and EC and the positive correlation among OC, N, P and K contents were in similarity to the findings of Ramulu et al. (2026) [15] .

Scatter plots of strongest relationship among the soil physico-chemical and chemical properties

The scatter plots showed significant linear relationships among the selected soil properties and available nutrients. Soil pH exhibited the strongest positive association with EC (r = 0.620), followed by available P with K (r = 0.481) and organic carbon with available N (r = 0.398). In contrast, available P showed a significant negative association with Zn (r = -0.375), indicating an inverse relationship between P and Zn availability. Overall, the scatter plots confirmed the trends

International Journal of Advanced Biochemistry Research https://www.biochemjournal.com observed in the Pearson correlation matrix, with the relationships being statistically significant at P < 0.001.

Conclusions

 Application of Organic manures and incorporation of crop residues can improve the soil organic carbon, nutrient cycling and sustain long term fertility.  Integrated nutrient management involving organic manures, crop residue incorporation, legume-based crop rotations and judicious application of nitrogen fertilizers should be adopted to improve nitrogen availability and sustain crop productivity.  Phosphate solubilising Organisms is to be added to high P soils inorder to increase the plant P content and judicious use of P fertilisers based on soil test and recommendations.  K and S should be applied based on the soil test recommendations as the contents in soil was observed at higher rate due to higher fertilizer imposition to soils.  Application of zinc fertilizers such as ZnSO₄ should be included in nutrient management programmes wherever deficiency is identified to prevent yield losses and improve crop growth.

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