Soil Fertility Mappingto identify Soil Related Production Constraints at Regional Agricultural Research Station, Palem, Telangana

Soil Fertility Mappingto identify Soil Related Production Constraints at Regional Agricultural Research Station, Palem, Telangana

Kasthuri Rajamani1* , J. Veeranna2 , N. Hari3 , M Venkata Ramana1

1*Regional Agricultural Research Station, Palem, Professor Jayashankar Telangana State Agricultural University, Nagarkurnool, Telangana, India.

2Agricultural College, Palem, Prof. Jayashankar Telangana State Agricultural University, Nagarkurnool, Telangana, India.

3Agricultural College, Aswaraopet, Prof. Jayashankar Telangana State Agricultural University, Khammam, Telangana, India.

Corresponding Author Email: Agricultural College, Aswaraopet, Prof. Jayashankar Telangana State Agricultural University, Khammam, Telangana, India.

DOI : CHE.2021.v02i04.024


The study was conducted to evaluate the major and micronutrient status of Regional Agricultural Research Station (RARS), Palem of Professor Jayashankar Telangana State Agricultural University (PJTSAU), Nagarkurnool District, Telangana. A total of 150 soil samples were collected by gird method at a depth of 0-15 cm and analyzed for soil pH, electrical conductivity (EC), organic carbon (OC), available nitrogen (N), phosphorus (P2O5), potassium (K2O), sulphur (S) and micronutrients (Zn, Cu, Fe, Mn and B) by following standard methods, further Arc-GIS software was used to prepare soil fertility maps. The farm soils were strongly acidic to moderately alkaline in reaction, and non-saline. The mean values of analyzed soil samples were low in organic carbon (0.35%), available nitrogen (136.51 kg ha-1), sulphur (6.13 mg kg-1), and boron (0.33 mg kg-1)content. Further, the mean values of farm soils exerted medium to high in available phosphorus & potassium (69.44 and 423.32 kg ha-1 respectively) status. Micronutrients viz., Zn, Cu, Fe and Mn registered beyond the acceptable range of 1.45, 2.05, 15.27 and 26.53 mg kg-1, respectively. The generated soil fertility status information can serve as an effective tool for site specific nutrient management for scientists and extension professionals to build future research strategies based on the determined soil fertility status.


Arc-Gis, GPS-GIS, soil fertility maps and nutrientindex, soil properties

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Soil fertility, productivity, and erodibility are the elements of soil quality, whereas nutrient imbalances are the major constraints for crop production in India’s semi-arid tropical (SAT) regions. The estimation of soil fertility encompasses the measurement of available macro and micronutrients and the evaluation of soil capacity to supply nutrients to plants [32]. The predominance of rainfed farming coupled with deficiencies of essential nutrients such as N (11-76%), P (21-74%), S (46-96 %) and Zn (62%) in Telangana soils [31] and are the major limiting factors for crop production. If intensive cropping is continued over a period without balanced fertilization to restore nutrients in the soil leads to a reduction in soil fertility, and crop yields are inevitable. Hence, information related to nutrient limitations and their reasonable management practices has greater significance to improve crop production for the sustainable development of agriculture. Soil test-based nutrient management, crop rotation, scientific application of chemical and bio-fertilizers are the need of the hour to maintain soil quality and to improve productivity [17]. Though conventional methods provide information on production constraints, those are slow and time-consuming. Global Positioning System (GPS) helps identify production constraints quickly and easy to formulate site-specific nutrient management practices to understand the status of soil fertility spatially and temporally. Further, Geographical Information System (GIS) provides valuable support to handle voluminous data generated through conventional and spatial format. The evaluation of farm-level fertility status of soil provides the necessary information on nutrient status, which can help the researchers and farmers apply need-based inputs for crop production and balance the soil ecosystem for a particular area. In this present study, we evaluated the fertility status (pH, EC, OC, N, P2O5, K2O, S, Zn, Cu, Fe, Mn and B) of the Regional Agricultural Research Station comprising150 acres at Palem village of Nagarkurnool district, Telangana to find out the soil fertility related production constraints of the farm to suggest remedial measures for optimum production of crops.


Regional Agricultural Research Station (RARS), Palem, was established in the year 1980 under Professor Jayashankar Telangana State Agricultural University (PJTSAU), Nagarkurnool District, Telangana. The farm is located at 16° 35´N latitude and 78° 01´ E longitude and is characterized by hot and dry with an average rainfall of 853 mm annually received mostly from the south-west monsoon. There are 19 types of soils in the Southern Telangana Zone, consists red clayey soils (22.3%), red gravelly loam (16.5%) and alluvio-colluvial soils (14.4% of the area). As a whole, the zone is dominated by different textured red soils with varied depths to the extent of 54.8 percent and is followed by alluvio-colluvial soils and calcareous soils (11.2%). The groundwater table is a deficit, ranging from -20 to 50 percent(Status of Ground Water Scenario, Goverenment of Telangana, 2019).

A total of 150 georeferenced surface soil samples (0-15 cm depth) were collected after harvest of the crops on-grid basis according to operational guidelines given by Department of Agriculture and Cooperation, Government of India for rainfed areas [8]. The samples were properly labeled, air-dried and processed for further analysis of soil parameters. The physico-chemical soil properties (pH and EC) were determined by standard procedures [12], whereas organic carbon content was estimated by wet oxidation method [40]. Available nitrogen (N) estimated by alkaline permanganate method [35], while available phosphorus (P) determined by sodium bicarbonate (0.5N NaHCO3) extractant at pH 8.5 [23], and available potassium (K) extracted by neutral normal ammonium acetate and measured on flame photometer [22]. The available sulphur estimated turbidimetrically by using  0.15%  CaCl2 [7], while available micronutrients (Zn, Cu, Fe and Mn) were extracted by DTPA extractant [20] and determined in Atomic Absorption Spectrophotometer (AAS) and hot water-soluble boron analyzed utilizing method [4]. Descriptive statistics viz., mean, median, maximum, minimum and standard deviation were determined using SPSS 16.0 version. Further,  Nutrient Index Value (NIV) was calculated by Ramamoorthy and Bajaj’s [27] index method after classification of soil samples based on soil test values of different nutrients in three categories viz., low, medium and high and calculated by following equation.

NIV = (NL × 1 + NM × 2 + NH × 3) / Total No.of samples

where, NL, NM and NH are the number of samples in low, medium and high fertility classes of nutrient status, respectively, and NT is the total number of samples. The index values are rated into various categories viz., low (<1.67), medium (1.67-2.33) and high (>2.33)for OC and available N, P and K. For available S and micronutrients, the ratings are very low (< 1.33), low(1.33-1.66), marginal (1.66-2.00), adequate (2.00-2.33), high (2.33-2.66) and very high (> 2.66). The research blocks were categorized into different fertility ratings based on percent sample category and NIV.


pH and Electrical Conductivity(EC)

Soil pH is one of the most important characteristics of soil fertility because it directly impacts nutrient availability and plant growth [11]. The soil pH varied from 5.94 to 8.05, with a mean value of 6.96 (Table 1). The distribution soil pH varied from strongly acidic to moderately alkaline, but a major area was found in nearly neutral (6.5-7.0) range. Different soil management practices and crop allocation at different research blocks of the farm for a longer period might be the reason for variations in soil pH (strongly acidic to moderately alkaline) variation. About 17.33 % of the samples were found to be moderately alkaline, 12.66 % were slightly alkaline and 50% of the samples fall into a neutral range. As well as 20% of samples were in a strong acidic state, which reduces nutrient availability and affects root growth [9] and can be ameliorated by applying agricultural lime. Further, the use of organic manures, biofertilizers, diversified crop rotations, minimum tillage, and cover crops were helpful to build soil organic matter to improve soil buffering capacity to change soil pH.

Soil conductivity is influenced by many factors, where high conductivities are usually associated with clay-rich soils and low conductivities are associated with sandy and gravelly soils. The electrical conductivity of research blocks varied from 0.05 to 0.57 dS m-1 with a mean of 0.15 dS m-1 indicated as non-saline nature of these soils (Table.1), which indicates that entire research blocks were normal (<1.0 dS m-1) and suitable for all crops to grow to reach the research station mandate. Similar results were also reported [25] at Regional Agricultural Research Station, Jagtial district of the same state.

Organic carbon (%)

Organic matter is a vital parameter for making soil alive by improving soil physical, biological and chemical properties [10]. The organic matter varied from 0.19 to 0.49% with a mean of 0.35% (Table 1). The distribution of organic carbon content at farm soils observed as low, i.e.,<0.5% of its categorization attributed due to higher temperature prevailing in the area associated with faster decomposition of organic matter resulting in the low organic carbon content of farm soils [26]. Based on a long-term fertility experiment on the rice-rice cropping system, [36] observed that the soil organic carbon stocks increased after 25 years (1980-2005) of regular application of organic sources by following best management practices for crop growth at Telangana soils.

Available Major (N, P and K) Nutrient Status in kg ha-1

The available Nitrogen (N) content (kg ha-1) ranged from 100.35 to 188.16with a mean of 136.51 kg ha-1(Fig.1). The entire farm soils were low as per available N categorization i.e.,< 280 kg available nitrogen ha-1. Among them, 65.62% of samples have <140 kg available nitrogen ha-1, and the rest of the samples varied between 140 to 188.16 kg available nitrogen ha-1. These results were similar to the study conducted at Nagarkurnool district [26], where the soils are coarse in texture coupled with high temperature and aerated conditions facilitated ammonia volatilization, leaching, runoff and de-nitrification. The nutrient index value registered as 1.00 indicates the overall fertility rating for available nitrogen status was low. It signifies the full dose (100%) of recommended nitrogen fertilizers for an adequate supply of nitrogen for different crops grown at research farm. Applying the recommended dose of N fertilizers at peak stage of crop demand is key to N management and optimum irrigation to avoid excessive leach of N below the root zone to obtain higher yields [4].

The available phosphorus (P2O5) ranged from 52.47 to 87.44 kg ha-1 with a mean of 69.44 kg ha-1 (Fig.1) and is a determining element for soil fertility and crop cultivation. The distribution of available phosphorus was medium to high in the study area, and high phosphorus levels were dominant in the working area might be due to the continuous application of phosphatic fertilizers for every crop without knowing the phosphorus supplying capacity of the soil [38]. At the study area, 90.62% of soils were in high status of available phosphorus, whereas only 9.375% of soils pose medium status, and suggested to reduce 30% of recommended phosphorus dose [16] to increase nodule bacteria activity, especially in legumes to fix the nitrogen in the soil. The farm soils registered a nutrient index value of 2.98 by specifying a higher category of available phosphorus, where the simpler compounds of calcium such as mono and dicalcium phosphates, are readily available for plant growth.

The available Potassium (K2O) content ranged from 266.11 to 520.13 kg ha-1 with a mean of 423.32kg ha-1and revealed that analyzed samples were medium to high in available potassium content (Fig.1), which taken up by plants relatively large proportions during crop growing season [3]. Among the analyzed samples, 15.64% were in medium status (145 to 340 kg K2O ha-1) of available potassium, whereas 84.36% samples registered as high status, having > 340 kg ha-1 of its categorization. This high level of available K at the study area may be due to potassium-rich parent material in the soils and dissolution of potassium-bearing minerals under alkaline conditions [28]. Further, it is suggested to apply 50% of recommended potassium dose is sufficient for farm soils where the available potassium is determined as high, and other research blocks should apply recommended dose of potassium fertilizers to accelerate nutrient catalytic function in various crops grown in research fields. The nutrient index value registered as 2.96 of its higher category, where the soils pose larger amounts of exchangeable and non-exchangeable K forms[33]. 

Available Sulphur (mg kg-1) status

The available sulphur (S) ranged from 4.38 to 8.75 mg kg-1 with an overall mean of 6.13 mg kg-1 indicating the entire study area was in deficient status (Table.2), which is very essential for plant growth due to its presence in proteins, phytochelatins, chloroplast membrane, and certain coenzymes and vitamins [37]. At the study area, 17.11% of samples registered too low sulphur content (<5 ppm), and 82.89% of samples found in low status of its categorization (<10 ppm), due to low organic carbon content at the study area [17]. The nutrient index value registered as 1.00 which indicates the overall fertility rating for available sulphur status was low and signifies the full dose (100%) of recommended sulphur fertilizers required for crops grown in the research farm. The intense cultivation of crops without applying sulphur-containing fertilizers might cause available sulphur deficiency in the farm soils. Being its critical content, application of 15-30 kg S ha-1 is mandatory to reduce sulphur deficiency stress [40], and simultaneously care should be taken while applying sulphur-containing fertilizers as they have acidity causing nature.

Available Micronutrients (Zn, Cu, Fe, Mn and B) status in mg kg-1

The available zinc (Zn) content ranged from 0.34 to 5.12 mg kg-1 with a mean value of 1.45 mg kg-1 as represented in Fig.(2), which is an essential element for healthy growth of plants and associated with chlorophyll development in leaves [9]. At the study area, most samples, i.e., 90.62%, had more than 0.60 mg kg-1 of available zinc content of its critical level, which indicates the sufficiency, and  9.38% of soils were insufficient status of available zinc. In zinc-deficient soils, plants suffer from physiological stress and cause the dysfunction of enzymatic and other metabolic functions [24]. The nutrient index of available zinc was noticed as 2.90. The tested soil samples revealed that the majority of the farm soils have sufficient status of available Zn due to regular application of zinc-containing fertilizers according to the crop requirement [6].

The available copper (Cu) in the farm soils varied from 0.39 to 4.96 mg kg-1 with an average value of 2.05 mg kg-1 as presented in Fig.(2), which is an important enzyme activator for crop production [18]. The entire farm soils registered >0.20 mg kg-1 of available copper content, indicating that the entire analyzed soil samples had sufficient status of available copper. Continuous application of copper-containing manures, inorganic fertilizers, and fungicides may reduce seed germination, inhibition of root and shoot growth, disturbance on photosynthetic pigments [1]. The nutrient index value registered as 3.00 which indicates the high category, being high status of available copper in the soil, care should have to taken during fungicide, pesticides, herbicides application in the field because these agro-chemicals, which already contains a copper element [29].

The available iron (Fe) content in the farm was ranged from 7.80 to 29.02 mg kg-1 with an average of 15.27 mg kg-1as depicted in Fig.(2), and it plays an important role in various metabolic processes [30]. The research farm soils recorded > 4.00 mg kg-1 of available Fe content of its critical level and showed sufficiency of its content, which plays an essential role for DNA synthesis, respiration, and photosynthesis [15]. The nutrient index found as 3.00, and excess sufficiency of the nutrient might be due to the cultivation of crops in alkaline & calcareous soils with various sources of organic and inorganic materials, which have the potential to maintain soluble Fe, and roots can assimilate Fe from applied compounds [2].

The farm soils’ available manganese (Mn) content ranged from 6.90 to 36.40 mg kg-1 with an average of 26.53 mg kg-1 as presented in Fig.(2). Manganese is an important micronutrient, which serves as a cofactor to activate numerous enzymes involved in the catalysis of oxidation-reduction, decarboxylation and hydrolytic reactions in plants [14]. The entire farm soils registered > 2.00 mg kg-1 of available Mn content of its critical level and showed excess content in the soil. It may be due to the cropping pattern, farming practices, and high available manganese content. The higher nutrient index value observed as 3.00, and this high content of available manganese may show toxicity stress on crop growth, therefore amelioration of farm soils is a prerequisite for reducing manganese toxicity stress [21].

The available boron (B) content of the study area ranged from 0.19 to 0.47 mg kg-1 with an average of 0.33 mg kg-1 as presented in Table.(2), which enhances the development of reproductive parts and carbohydrate metabolism. At the study area, entire farm samples were found in low status of its categorization (<0.52 ppm), due to low organic carbon content which greatly affects the absorption of boron at the study area [34]. Furthermore, boron deficiency affects the photosynthetic capacity and transportation of photosynthetic products [19] to the growing parts. The nutrient index value registered as 1.00 which indicates the overall fertility rating for available boron status was low, which signifies the full dose (2 kg ha-1) of recommended boron supplying fertilizers required for crops grown in the research farm


The study indicated that the soils of Regional Agricultural Research Station, Palem are strongly acidic to slightly alkaline in reaction and non-saline. The mean values of farm soils were low in organic carbon (0.35%), available nitrogen (136.51 kg ha-1), available sulphur and boron (6.13 and 0.33 mg ka-1 respectively) content. They suggested to incorporate organic manures, crop residues and to follow cover cropping with crop rotation practices. The mean values of farm soils exerted medium to high available phosphorus & potassium (69.44 and 423.32 kg ha-1 respectively)status, and sufficient in micronutrients viz., Zn, Cu, Fe and Mn (1.45, 2.05, 15.27 and 26.53 mg kg-1 respectively) content, further advocated to avoid indiscriminate use of fertilizers where the nutrient status is high and apply recommended dose of fertilizers as per crop need. For sustainable and precise management of research fields, it is essential to know the spatial distribution of soil nutrients, which aim to increase the crops’ productivity. Further, this information will be useful to researchers to build up future research strategies to enhance soil quality and biodiversity.

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  1. Adrees M, Ali S, Rizwan M, Ibrahim M, Abbas F, Farid, M, Bharwana SA. The effect of excess copper on growth and physiology of important food crops: A review. Environmental Science and Pollution Research. 2015;22(11):8148-8162.
  2. Ahmad, F., Muhammad Aamer Maqsood1, Tariq Aziz and Mumtaz Akhtar Cheemaak. Water soluble Iron (Fe) concentration in Alkaline and Calcareous soils Influenced by various Fe sources. Journal of Agricultural Sciences. 2014, Vol. 51(2), 417-421.
  3. Anderson, M. Peterson, and D. Curtin, “Base cations, K+ and Ca2+, have contrasting effects on soil carbon, nitrogen and denitrification dynamics as pH rises,” Soil Biology and Biochemistry, 2017(113):99–107
  4. Balasubramanian V, KP Ragunath, R Srinivasan, E Manikandan, S Parvathy and M Jayakumar.Spatial variability of soil nutrients and GIS-based nutrient management in upland of Tamil Nadu: A case study from Valapadi Block, Salem district. International Journal of Chemical Studies, 2020:8(2)-2801-2809, Issue 2 (2020) DOI: 10.22271/chemi.2020.v8.i2aq.9173
  5. Berger, K.C. and Truog, E., Boron determination in soils and plants using the quinalizarin  reaction.IndustrialEngg.  Chem.  11:540-545(1939).
  6. Bhatt R, Hossain A and Sharma P. 2020. Zinc biofortification as an innovative technology to alleviate the zinc deficiency in human health: A review. Open Agriculture 5: 176–87.
  7. Chesnin   L,   Yien CH.   Turbidimetric determination of available sulphur. Soil Science  Society  of  American Journal. 1951;15:149-151.
  8. Department of Agriculture and Cooperation (DoAC) Ministry of Agriculture and Farmers Welfare. National Mission for Sustainable Agriculture. Operational Guidelines; 2014. Available:
  9. Havlin HL, Beaton JD, Tisdale SL, et al. Soil Fertility and Fertilizers- an introduction to nutrient management. 7th ed. India: PHI Learning Private Limited; 2010.
  10. Hoffland, E., Kuyper, T.W., Comans, R.N.J. et al. Eco-functionality of organic matter in soils. Plant Soil 455, 1–22 (2020).
  11. Holland, J.E.; Bennett, A.E.; Newton, A.C.; White, P.J.; McKenzie, B.M.; George, T.S.; Pakeman, R.J.; Bailey, J.S.; Fornara, D.A.; Hayes, R.C. Liming impacts on soils, crops and biodiversity in the UK: A review. Sci. Total Environ. 2018, 610–611, 316–332.
  12. Jackson ML. Soil chemical analysis. Prentice Hall of India Pvt. Ltd. New Delhi;1973.
  13. Kasthuri Rajamani, Hari N and Rajashekar M. Fertility Evaluation and GPS-GIS Based Soil Nutrient Mapping of Krishi Vigyan Kendra, Palem, Telangana  International Research Journal of Pure & Applied Chemistry 21(23): 139-145, 2020.
  14. Katkar, R.N. and Patil, D.B. Available micronutrient content in soils of Vidarbha. Souvenir of State Level Seminar in Dept. of Soil Science and Agriculture Chemistry, PDKV, Akola organized during Jan. 2-3, 2010. pp. 161-166.
  15. Khadka, D., Lamichhane, S., Bhurer, K.P., Chaudhary, J.N., Ali, M.F., Lakhe, L., 2018. Soil Fertility Assessment and Mapping of Regional Agricultural Research Station, Parwanipur, Bara, Nepal. Journal of Nepal Agricultural Research Council 4(28): 33-47.
  16. Kumar D, Yadav S R., Kaur R, Choudhary A and Meena B S. Soil fertility status and nutrient recommendations based on soil analysis of Jaisalmer district of western Rajasthan. Asian Journal of Soil Science.2017. 12: 103-07.
  17. Kumar, H., Sahu, K.K., Kurre, P.K., Goswami, R.G. and Kurrey, C.D. 2014. Correlation studies on available sulphur and soil properties in soils of Dabhra block under Janjgir-Champa district in Chhattisgarh. Asian Journal of Soil Science 9: 217-220.
  18. Laporte, D., Valdés, N., González, A., Sáez, C. A., Zúñiga, A., Navarrete, A., et al. (2016). Copper-induced overexpression of genes encoding antioxidant system enzymes and metallothioneins involve the activation of CaMs, CDPKs and MEK1/2 in the marine alga Ulva compressa. Aquat. Toxicol. 177, 433–440. doi: 10.1016/j.aquatox.2016.06.017
  19.  Li, M.; Zhao, Z.; Zhang, Z.; Zhang, W.; Zhou, J.; Xu, F.; Liu, X. E_ect of boron deficiency on anatomical structure and chemical composition of petioles and photosynthesis of leaves in cotton (Gossypiumhirsutum L.). Sci. Rep. 2017, 7, 4420.
  20. Lindsay WL, Norvell WA. Development of a DTPA soil test for zinc, iron, manganese, and copper. Soil Science Society of America Journal. 1978;42:421-428.
  21. Mousavi SR, Shahsavari M, Rezaei M. A general overview of manganese (Mn) importance for crops production. Australian Journal of Basic and Applied Sciences. 2011;5(9):1799–1803.
  22. Muhr GR, Datt NP, Sankasuramoney H, IeieyVK, Donahue L, Roy. Soil testing in India. United States Agency for International Development, New Delhi; 1965.
  23. Olsen SR, Cole CV, Watanabe FS, Dean LA. Estimation of available phosphorus in soils by extraction with sodium bicarbonate. Circulation from USDA. 1954;939.
  24. Paradisone, V., Navarro-León, E., Ruiz, J.M. et al. Calcium silicate ameliorates zinc deficiency and toxicity symptoms in barley plants through improvements in nitrogen metabolism and photosynthesis. Acta Physiol Plant 43, 154 (2021). [
  25. Raj GB, Kasthuri Rajamani and Kumara B. H. Influence of Silicon Fertilization on Nitrogen Fractions and Nutrient Status of Rice Grown Soils in Telangana State. Current Journal of Applied Science and Technology, 39(7): 26-34, 2020.
  26. Rajamani,K., A. Madhavi, T. Srijaya, P. SurendraBabu and PradipDey. On-farm Fertility Management through Target YieldmApproach for Sustenance of Tribal Farmers. Current Journal of Applied Science and Technology 39(43): 58-65, 2020
  27. Ramamoorthy B, Bajaj JC. Available NP, K status of Indian soils. Fertilizer News. 1969;14:24-26
  28. Riaz, Irshad Bibi, Nabeel Khan Niazi, Ghulam Murtaza, Humera Aziz, Umair. Potassium Release Kinetics from Dioctahedral and Trioctahedral Minerals under Alkaline Conditions. Global Journal of Science Frontier Research, [S.l.], apr. 2018. ISSN 2249-4626.
  29. Rodríguez, F., Laporte, D., González, A., Mendez, K. N., Castro-Nallar, E., Meneses, C., et al. (2018). Copper-induced increased expression of genes involved in photosynthesis, carotenoid synthesis and C assimilation in the marine alga Ulva compressa. BMC Genomics 19, 829. doi: 10.118/2Fs12864-018-5226-4
  30. Rout, G. R., Sahoo, S., 2015. Role of iron in plant growth and metabolism. Reviews in Agricultural Science 3(1): 1-24.
  31. Sahrawat, K.L. and Wani, S.P. 2013. Soil testing as a tool for on-farm soil fertility management: experience from the semi-arid zone of India. Soil Science and Plant Analysis 44: 1011-1032.
  32. Schjoerring JK, I Cakmak, PJ White (2019). Plant nutrition and soil fertility: synergies for acquiring global green growth and sustainable development. Plant Soil, 434, 1–6 s11104-018-03898-7
  33. Shakeri, S. and S.A. Abtahi. 2018. Potassium forms in calcareous soils as affected by clay minerals and soil development in Kohgiluyeh and Boyer-Ahmad Province, Southwest Iran. J. Arid Land. 10(2): 217–232.
  34. Shireen, F., Nawaz, M. A., Chen, C., Zhang, Q., Zheng, Z., Sohail, H., Sun, J., Cao, H., Huang, Y., &Bie, Z. (2018). Boron: Functions and Approaches to Enhance Its Availability in Plants for Sustainable Agriculture. International journal of molecular sciences, 19(7), 1856.
  35. Subbaiah BV, Asija GL. A rapid procedure for the determination of available nitrogen in soils. Current Science. 1956;25:259-260.
  36. Suresh, M., G. Jayasree, M. Srilatha, S. Narender Reddy and Kiran Reddy, G. 2017. Effect of Long Term Fertilizers and Organic Manures on Key Soil Quality Indicators and Indices in Rice – Rice Cropping System. Int.J.Curr.Microbiol.App.Sci. 6(10): 2727-2735. doi:
  37. Takahashi, H., Kopriva, S., Giordano, M., Saito, K., Hell, R., 2011. Sulfur assimilation in photosynthetic organisms: molecular functions and regulations of transporters and assimilatory enzymes. Annual Review of Plant Biology 62: 157-184.
  38. Vasu D, Singh SK, Sahu N, Tiwary P, Chandran P, Duraisami VP et al. Assessment of spatial variability of soil properties using geospatial techniques for farm level nutrient management. Soil & Tillage Res. 2017; 169:25-34.
  39. Walakley A, Black CA. Estimation of organic carbon by chromic acid titration method. Soil Science. 1934;37:29-38.
  40. Zenda, T.; Liu, S.; Dong, A.; Duan, H. Revisiting Sulphur: The Once Neglected Nutrient: It’s Roles in Plant Growth, Metabolism, Stress Tolerance and Crop Production. Agriculture 2021, 11, 626.