Characterization and classification of soils using morphological and physicochemical properties in major barley-growing areas of Rajasthan

Introduction

Barley (Hordeum vulgare L. is a very old cultivated cereal which comes in fourth in global production behind maize, wheat and rice (Pal et al., 2012) [19] . It is a popular choice for food, feed and malting grain due to its nutrition and industrial value (Baik and Ullrich, 2008) [4] . Also it is a good source of dietary fiber which in particular is of beta glucan that which gives it health and nutraceutical benefits (Newman and Newman, 2006) [17] . In India barley is mainly grown in marginal and resource poor areas which includes Rajasthan, Uttar Pradesh, and Haryana. In 2022-23 barley covered about 0.62 million hectares which produced a total of 1.84 million tonnes (Anonymous, 2023). Rajasthan is one of the major barley-growing states of India; however, variability in soil properties across different agro-climatic regions significantly influences crop productivity and quality. Soil characterization provides information on important properties such as soil colour, texture, structure, consistency, drainage, and horizon development, which help in understanding soil potential and identifying production constraints. Physicochemical properties including soil reaction, electrical conductivity, organic carbon, cation exchange capacity, and nutrient status also play a vital role in determining soil fertility and suitability for barley cultivation. Soil classification is important for grouping soils based on their physical, chemical, and mineralogical characteristics and for developing suitable management practices for sustainable crop production (Sharu et al., 2013) [24] . In addition, land capability and irrigability classifications help in assessing the sustainable agricultural use of soils under different management conditions (Palaskar et al., 1987) [20] . Therefore, the present investigation was undertaken to characterize capacity (CEC) was determined using neutral normal ammonium acetate (Metson, 1956) [16] . Calcium carbonate content was estimated by the acid neutralization method (Allison and Modi, 1965) [1] . Exchangeable sodium and potassium were determined using ammonium acetate extraction, while exchangeable calcium and magnesium were estimated using KCl-triethanolamine buffer extraction followed by EDTA titration (Jackson, 1967) [9] . Available nitrogen, phosphorus, and potassium were estimated by the alkaline permanganate method (Subbiah and Asija, 1956) [27] , Olsen's method (Olsen et al., 1954) [18] , and neutral normal ammonium acetate extraction followed by flame photometric determination (Merwin and Peech, 1951) [15] , respectively. DTPA-extractable micronutrients (Fe, Mn, Zn, and Cu) were determined using an atomic absorption spectrophotometer (Lindsay and Norvell, 1978) [12] . Further, the studied soil characteristics served as the basis for land capability, irrigability, and suitability classification of the soils. Land Capability Classification (LCC) grouped soils into Classes I to VIII based on limitations such as slope, erosion, drainage, wetness, and soil depth, where Classes I and II were considered most suitable for cultivation, while Classes V to VIII were generally unsuitable for regular cropping. Land Irrigability Classification categorized soils from S1 (highly suitable) to N2 (not suitable) according to slope, erosion hazard, and drainage conditions affecting irrigation potential. Similarly, land suitability classification assessed soils as S1 (highly suitable), S2 (moderately suitable), S3 (marginally suitable), N1 (currently unsuitable but improvable), and N2 (permanently unsuitable) depending on the severity of soil and land limitations. Overall, land suitability and irrigability decreased with increasing slope, erosion risk, drainage problems, and other soil constraints.

Results and Discussion

Morphological Properties of Soils

The soils of Sri Ganganagar, Udaipur, and Sikar districts exhibited marked variation in morphological and physical characteristics due to differences in physiography and pedogenic processes. Sri Ganganagar and Sikar soils were predominantly coarse-textured, consisting of sand to loamy sand, with weak horizon development, weak to moderate blocky structure, and calcium carbonate accumulation in subsurface horizons. Soil colours ranged from light brownish grey to pale brown, with increasing effervescence at depth indicating their calcareous nature. In contrast, Udaipur soils showed comparatively better profile development with distinct Ap, Bw, and Bt horizons, darker surface colours, moderate subangular blocky structure, and evidence of clay illuviation. Mechanical analysis revealed the dominance of sand in Sri Ganganagar (67.48-89.81%) and Sikar (75.10-90.20%) soils, whereas Udaipur soils contained relatively higher silt (9.43-26.36%) and clay (6.57-58.50%) contents. Clay content ranged from 1.42-11.04% in Sri Ganganagar and 3.20-13.30% in Sikar soils. The predominance of sand in Sri Ganganagar and Sikar soils reflects the influence of aeolian deposits under arid conditions, while the finer texture of Udaipur soils contributes to greater water-holding capacity and nutrient retention. Overall, the coarse texture, weak horizon differentiation, and calcium carbonate accumulation in Sri Ganganagar and Sikar soils are characteristic of arid-region pedogenesis, whereas the better-developed and finer-textured Udaipur soils reflect the influence of relatively higher rainfall and organic matter content (Meena et al [14,25,26,10] . Overall, the physical properties were strongly influenced by soil texture and organic matter content. Coarse-textured soils of Sri Ganganagar and Sikar districts exhibited relatively higher bulk density, lower porosity, and reduced water holding capacity, characteristics commonly associated with sandy soils of arid and semi-arid regions. In contrast, the Udaipur soils showed lower bulk density, higher porosity, and greater moisture retention due to relatively finer texture and better pedogenic development. These findings are in agreement with earlier reports by Arya et al., (2025), Vedadri and Naidu (2018) [30] , Swarnam et al., (2004) [28] , and Singh and Rathore (2017) [26] .

Physico-Chemical Properties

The chemical properties of the soils varied considerably among locations and profiles. Soil reaction (pH) ranged from 7.1 to 8.9, indicating neutral to strongly alkaline conditions. Sri Ganganagar soils were moderately to strongly alkaline (8.1-8.9), Udaipur soils were near neutral to mildly alkaline (7.1-7.7), and Sikar soils were moderately alkaline (8.0-8.6). The higher pH in Sri Ganganagar and Sikar soils was attributed to calcium carbonate accumulation under arid conditions, whereas the comparatively lower pH of Udaipur soils reflected greater weathering and leaching (Kumar et al., 2022; Arya et al., 2025) [10] . Electrical conductivity (EC) ranged from 0.10 to 0.20 dS m ¹ in Sri Ganganagar, 0.10 to 0.70 ⁻ dS m⁻¹ in Udaipur, and 0.19 to 0.23 dS m ¹ in Sikar soils. All the soils were non-saline to slightly saline ⁻ and remained within safe limits for barley cultivation. Organic carbon content varied from 0.04 to 0.57 per cent and generally decreased with depth. Udaipur soils recorded comparatively higher organic carbon (0.37-0.57%), followed by Sikar (0.17-0.29%) and Sri Ganganagar soils (0.04-0.20%). Higher organic carbon in Udaipur soils may be attributed to finer texture and better vegetation cover (Meena et al., 2012; Singh and Rathore, 2017) [14,26] . Exchangeable sodium, potassium, calcium, and magnesium ranged from 0.03-1.47, 0.10-0.59, 2.50-19.22, and 1.17-9.89 meq 100 g ¹, respectively. Calcium was the dominant exchangeable ⁻ cation, followed by magnesium, sodium, and potassium. Cation exchange capacity (CEC) ranged from 5.1 to 43.2 meq 100 g⁻¹ and was generally higher in Sri Ganganagar and Udaipur soils. Exchangeable calcium and magnesium increased with depth in Sri Ganganagar and Sikar soils due to carbonate accumulation and limited leaching (Singh and Rathore, 2015; Arya et al., 2025) [25] . Higher CEC and exchangeable bases in Udaipur soils were associated with greater clay and organic matter content, resulting in better nutrient retention capacity (Meena et al., 2012; Kumar et al., 2022) [14,10] . [14,25,7,8] . [26,13] . [21,33] . [6,11,34] .

Irrigability Classification

Conclusions

The study demonstrated considerable variability in the morphological, physical, physico-chemical, and fertility characteristics of soils from the major barley-growing regions of Rajasthan. Udaipur soils exhibited better profile development, finer texture, higher organic carbon content, and greater nutrient availability, resulting in higher land capability, better irrigability, and suitability classes ranging from S1 to S2 for barley cultivation. In contrast, the soils of Sri Ganganagar and Sikar were predominantly coarse-textured, moderately alkaline, and low in organic carbon and available nutrients, leading to lower land capability and moderate to marginal suitability (S2-S3). Soil texture, depth, drainage, alkalinity, and nutrient status were identified as the key factors governing barley suitability. The findings emphasize the importance of integrated soil management practices, including organic matter addition, balanced nutrient application, and alkalinity management, to enhance soil productivity and ensure sustainable barley cultivation in the arid and semi-arid regions of Rajasthan.

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