Mapping the distribution of micro nutrients in soils of Washim district: A spatial analysis

Introduction

Soils are inherently heterogeneous, with dynamic properties that change over time and space due to various interacting factors (Ramzan et al., 2017) [1] . Soil fertility, a key determinant of crop productivity, is influenced by soil pH, organic matter, texture, and biological activity. Continuous nutrient depletion due to intensive cropping necessitates periodic soil fertility assessment. In India micronutrient deficiency in soil was reported by (Shukla et al., 2019) [2] according to results from the analysis of more than 2.0 lakh soil samples collected from 508 districts of the country, on average 36.5, 12.8, 7.1 and 4.2% of soils are deficient in Zn, Fe, Mn and Cu respectively. More than 50% of samples are found deficient in Zn in 110 districts of the country over the years, Zn deficiency has declined in soils of the country because of regular and more use of Zn fertilizer whereas deficiency of Fe and Mn increased slightly. Most of the times soil sampling will be done without geographic reference. The results of such samples will be of little use and continuous monitoring of soil fertility status will be very difficult. Indian agriculture in recent years progressed dramatically owing to modernization, mechanization and use of advance technologies. Using these advance technologies like GIS, GPS and remote sensing can evaluate the spatial variability of soil fertility for precise nutrient management in a large area easily and effectively in very less time. Global Positioning System (GPS) helps in evaluating the soil fertility status of soil time to time and also helps in making critical decisions on nutrient management (Patil et al., 2017) [3] . Unfortunately, due to intensive cultivation practices and inadequate use of chemical fertilizers, the fertility and productivity of agricultural soil are declining. Moreover, the heavy application of chemical fertilizers and their diminishing responses pose alarming surface soil samples (0-20 cm) total 204 samples in Washim district were collected. The record of surveyed fields latitude, longitude using GPS with mean sea level was maintained. Soil pH and EC were determined in soil: water suspensions (1:2.5 w/v) as described by Jackson (1973) [4] . Organic carbon was determined by Walkley and Black wetoxidation method as given by Walkley and Black (1934) [5] . Free CaCO 3 was determined by rapid titration method (Piper, 1966) [6] . The available zinc, iron, copper and manganese were extracted with 0.005M diethylene triamine penta acetic acid (DTPA) and the concentrations of nutrients were determined on Atomic Absorption Spectrophotometer (Lindsay and Norvell, 1978) [7] . The nutrient indices were calculated by using the formula given by Parker et al.

(1951) [8] and Hadole et al (2024) [9] . Formula for Nutrient Index:

% samples acute x 1 + % samples deficient x 2 + % samples latent x 3 + % samples marginal sufficient x 4 + % samples adequate x 5 + % samples high x 6 Nutrient index = 100

Results and Discussion

Soil properties

The soil pH for Washim district, showing values ranging from 6.48 to 8.82 (Table 2) indicated a pH range from neutral to strongly alkaline. The highest pH of 8.29 was observed in soils of Karanja tehsil, while the lowest pH of 7.82 was recorded in Malegaon tehsil. The alkaline nature of the soil is likely attributed to the presence of adequate free lime content in the soil Priyanka et al. (2018) [10] . Soil electrical conductivity (EC) values ranging from 0.09 to 0.88 dS m -1 (Table 2), it shows that the soils in Washim district are predominantly non-saline, making them favourable for healthy plant growth. EC exceeding 1.0 dS m -1 indicates the presence of soluble salts, posing a risk to plant cultivation, Jackson (1967) [11] . The calcium carbonate content (CaCO 3 ) ranges from 1.13 to 22.63 percent (Table 2), which indicates that soil is non-calcareous to calcareous in nature. The highest content of calcium carbonate was recorded in Mangrulpir tehsil. High levels of CaCO 3 in soil can raise pH levels and lower the solubility of soil micronutrients, leading to nutritional and metabolic disorders in plants. These results are in accordance with the results reported by Katkar et al. (2013) [12] . Organic carbon content varied from 3.15 to 19.80 g kg -1 (Table 2). The organic carbon variation could be noticed in every tehsil with highest content observed in Risod tehsil, Malegaon tehsil and Karanja tehsil.

Status of micronutrient

All available micronutrient can be categories into acute deficient, deficient, latent deficient, marginal sufficient, adequate, high, categories. The available zinc in all over Washim district ranged from 0.28 to 2.65 mg kg -1 with a mean of 1.11 mg kg -1 (Table 3). [13] soil micronutrients status in Kalmeshwar tehsil, district Nagpur observed that, the DTPA-Zn was in the range of 0.62-1.14 mg kg -1 . The available iron in all over Washim district ranged from 3.28 to 30.08 mg kg -1 with a mean of 8.25 mg kg -1 (Table 4) shows that Washim district had moderate available iron contains in soils. Soil samples from all tehsils, including Washim, Mangrulpir, Manora, Karanja, Malegaon, and Risod, were found to be in the latent deficient (26.47%) category of available iron, followed by marginal sufficient (25.98%) and high (20.59%) categories. In the adequate and deficient categories, some samples were found at 13.73% and 13.24%, respectively. No soil samples were found in the acute deficient category. Iron deficiency was recorded to the extent of 39.71% in the soils of Washim district. The nutrient index value (Table 4) across the district was found to be in the medium range, that is (4.02). The highest nutrient index was recorded in Manora tehsil at (4.66), followed by Malegaon and Risod tehsils with values of (4.65) and (4.48), respectively. The lowest nutrient index value was observed in Washim tehsil, at (3.03). Mahashabde and Patel (2012) reported that available Fe range from 9.5-14.8 mg kg -1 from Shirpur tehsil region. The available copper in all over Washim district ranged from 1.12 to 15.55 mg kg -1 with a mean of 2.90 mg kg -1 (Table 5) showed that Washim district had very high available copper contains in soils. Soil samples from all tehsils, including Washim, Mangrulpir, Manora, Karanja, Malegaon, and Risod, were found in the high (100%) category of available copper. No acute deficiency was observed in any tehsils of Washim district. The copper deficiency was recorded to the extent of 0% in soils of Washim district. The nutrient index value (Table 5) in all over the district was found in high range i.e. (6.00). Magare et al. (2022) [15] studied that available Copper content in soils of Amravati district varies from 0.78 to 5.42 with a mean value of 3.37 mg kg -1 . The available manganese in all over Washim district ranged from 8.24 to 52.92 mg kg -1 with mean of 23.14 mg kg -1 (Table 6) shows that Washim district had very high available manganese contains in soils. In all tehsil most of the soil samples were found in high (97.06%) category of available manganese followed by only six sample found in adequate category (2.94%). The manganese deficiency was recorded to the extent of 0% in soils of Washim district. The nutrient index value (Table 6) in all over the district was found in high range i.e. (5.97). Magare et al. (2022) [15] studied that available Mn content in soils of Amravati district ranged from 5.68 to 35.41 with mean value of 16.21 mg kg -1 . The available boron in all over Washim district ranged from 0.01 to 7.88 mg kg -1 with mean of 1.86 mg kg -1 (Table 7) shows that Washim district had moderate available boron contains in soils. In all tehsils most of the soil sample were found in High (56.37%) category of available boron followed by Acute category (14.22%), Acute deficiency of available boron was observed in Manora, Karanja, Malegaon tehsil such as (17.24%), (28.57%), (37.84%), respectively. The boron deficiency was recorded to the extent of 33.83% in soils of Washim district. The nutrient index value (Table 7) in all over the district was found in high range i.e. (4.42).

Highest nutrient index was found in Risod tehsil (6.00) followed by Mangrulpir, Washim, Manora tehsil (5.97), (5.57) and (4.21).

Conclusion

The available zinc content in the soils of Washim district ranged between 0.28 to 2.65 mg kg -1 . Zinc deficiency was found 43.63% in the soils, with acute deficiency being notably common. The nutrient index value was classified as medium (3.99). The available iron content in the soils of Washim district ranged from 3.28 to 30.08 mg kg -1 . Iron deficiency was observed 39.71% in the soils, although acute deficiency was not detected. The nutrient index value was classified as medium (4.02). The available copper content in the soils of Washim district ranged from 1.12 to 15.55 mg kg -1 . The copper deficiency was not recorded in the soils of Washim district. The nutrient index value was classified as high (6.00). The available manganese content in the soils of Washim district ranged from 8.24 to 52.92 mg kg -1 . Manganese deficiency was not observed in the soils of Washim district. The nutrient index value was classified as high (5.97). The available boron content in the soils of Washim district varied from 0.01 to 7.88 mg kg -1 . Boron deficiency was observed 33.83% in the soils of Washim district. The nutrient index value was classified as medium (4.42).

Acknowledgement

I wish to express my profound sense of gratitude and sincere thanks to Head department of soil science Dr. Panjabaro Deshmukh Krishi Vidyapeeth Akola and project coordinate and All India Coordinated Research Project of Micro and Secondary Nutrients and Pollutant Elements, for providing facilities during the course of investigation Dr, PDKV Akola.

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