Eurasian Journal of Soil Science

Abstract

This study investigated the spatial variability of DTPA-extractable Fe, Mn, Zn, and Cu in a cultivated field, their relationships with selected soil properties, and the optimum number of samples required to estimate mean micronutrient concentrations precisely. Forty-nine soil samples were collected at 5-m intervals from a square grid within a 30 × 30 m cultivated plot. Mean DTPA-extractable concentrations were 71.80 mg kg⁻¹ for Fe, 350.26 mg kg⁻¹ for Mn, 2.58 mg kg⁻¹ for Zn, and 4.11 mg kg⁻¹ for Cu. The coefficients of variation were higher for Fe (20.6%) and Zn (19.2%) than for Mn (11.8%) and Cu (8.4%). Spatial variability was best described by spherical models for Fe and Mn and exponential models for Zn and Cu. The spatial correlation ranges followed the order Zn (67 m) > Cu (17 m) > Fe (15 m) > Mn (8 m). Nugget-to-sill ratios indicated strong spatial dependence for Fe (0.039%), Mn (8.03%), and Cu (11.32%) and moderate spatial dependence for Zn (42.86%). In principal component analysis, Fe, Cu, and soil organic matter (OM) had high negative loadings on PC1, whereas Zn contributed most strongly to PC2. Fe was positively correlated with soil OM and negatively correlated with Mn, Zn, pH, Ca, and Na. Mn was positively correlated with Zn and Cu, whereas Zn was positively correlated with silt and pH. Cu was negatively correlated with pH, Ca, Mg, and K. The numbers of samples required to estimate mean concentrations within allowable errors of 5%, 10%, and 20% followed the order Fe (69, 17, and 4) > Zn (59, 15, and 4) > Mn (23, 6, and 2) > Cu (11, 3, and 1), respectively. Thus, greater spatial variability in a micronutrient requires a larger sample size to estimate its field mean precisely.

Keywords

Soil properties, Fe, Mn, Zn, Cu, spatial dependence, sampling intensity.

References

<p>Aşkın, T., Kızılkaya, R., 2006. Assessing spatial variability of soil enzyme activities in pasture topsoils using geostatistics. <em>European Journal of Soil Biology</em> 42(4): 230&ndash;237.</p>

<p>Aşkın, T., T&uuml;rkmen, F., Tarak&ccedil;ıoğlu, C., Kula&ccedil;, S., Ayg&uuml;n, S., 2017. DTPA-extractable micronutrients: A geostatistical study from Ordu, Turkey. <em>Eurasian Journal of Soil Science</em> 6(2): 154&ndash;160.</p>

<p>Behera, S.K., Shukla, A.K., 2014. Total and extractable manganese and iron in some cultivated acid soils of India: Status, distribution and relationship with some soil properties. <em>Pedosphere</em> 24(2): 196&ndash;208.</p>

<p>Bo, S., Shenglu, Z., Qiguo, Z., 2003. Evaluation of spatial and temporal changes of soil quality based on geostatistical analysis in the hill region of subtropical China. <em>Geoderma</em> 115: 85&ndash;99.</p>

<p>Burrough, P.A., 1993. Fractals and geostatistical methods in landscape studies. In: Fractals in Geography. Lam, N., De Cola, L. (Eds.). Prentice Hall, Englewood Cliffs, NJ, USA, pp. 87&ndash;112.</p>

<p>Buttar, T.S., Sharma, V., 2023. Spatial variability of soil micronutrients under paddy (Oryza sativa)-wheat (Triticum aestivum) cropping system in irrigated plains. <em>Indian Journal of Agricultural Sciences</em> 93(4): 403&ndash;408.</p>

<p>Cambardella, C.A., Moorman, T.B., Novak, J.M., Parkin, T.B., Karlen, D.L., Turco, R.F., Konopka, A.E., 1994. Field-scale variability of soil properties in central Iowa soils. <em>Soil Science Society of America Journal</em> 58: 1501&ndash;1511.</p>

<p>Cameron, D.R., Nyborg, M., Toogood, J.A., Laverty, D.H., 1971. Accuracy of field sampling for soil tests. <em>Canadian Journal of Soil Science</em> 51(2): 165&ndash;175.</p>

<p>Chukwu, E.C., G&uuml;lser, C., 2025. Morphological, physiological, and anatomical effects of heavy metals on soil and plant health and possible remediation technologies. <em>Soil Security</em> 18: 100178.</p>

<p>&Ccedil;elim, S., G&uuml;lser, F., 2020. The changes caused by different ıron forms in growth of bean (Phaseoulus vulgaris L. Var Nana) under cadmium stress. <em>ISPEC Journal of Agricultural Sciences</em> 4(4): 1006&ndash;1023.</p>

<p>de Santiago, A., Quintero, J.M., Delgado, A., 2008. Long-term effects of tillage on the availability of iron, copper, manganese, and zinc in a Spanish Vertisol. <em>Soil and Tillage Research</em> 98(2): 200&ndash;207.</p>

<p>Demiralay, I., 1993. Soil physical analysis. Ataturk University Agricultural Faculty Publi,cations No. 143, Erzurum, T&uuml;rkiye. [in Turkish].</p>

<p>Demirkaya, S., G&uuml;lser, C., 2023. Effect of acidified biochar applications on DTPA extractable microelement content in a coarse textured soil. <em>Toprak Bilimi ve Bitki Besleme Dergisi</em> 11(1): 47&ndash;53. [in Turkish].</p>

<p>Dhaliwal, S.S., Naresh, R.K., Mandal, A., Walia, M.K., Gupta, R.K., Singh, R., Dhaliwal, M.K., 2019. Effect of manures and fertilizers on soil physical properties, build-up of macro and micronutrients and uptake in soil under different cropping systems: A review. <em>Journal of Plant Nutrition</em> 42(20): 2873&ndash;2900.</p>

<p>Dhaliwal, S.S., Sharma, V., Kaur, J., Shukla, A.K., Hossain, A., Abdel-Hafez, S.H., Singh, V.K., 2021. The pedospheric variation of DTPA-extractable Zn, Fe, Mn, Cu and other physicochemical characteristics in major soil orders in existing land use systems of Punjab, India. Sustainability 14(1): 29.</p>

<p>Gamma Design Software, 2010. GS+ Version 9: Geostatistical Software for the Environmental Sciences. Gamma Design Software LLC, Plainwell, Michigan, USA.</p>

<p>Guang, C., Jia, L., Huimin, H., Ruiying, D., Xu, W., 2022. Physiological and molecular mechanisms of plant responses to copper stress. <em>International Journal of Molecular Sciences</em> 23(21): 12950.</p>

<p>G&uuml;lser, C., 2023. Effect of soil tillage on soil organic matter in a clay field. <em>Agricultural Sciences</em> 15(38): 1-11.</p>

<p>G&uuml;lser, C., Ekberli, İ., Candemir, F., 2016. Spatial variability of soil physical properties in a cultivated field. <em>Eurasian Journal of Soil Science</em> 5(3): 192&ndash;200.</p>

<p>G&uuml;lser, F., Kara&ccedil;al, İ., 2015. Comparing the effects of organic and inorganic compounds of iron and zinc on fruit quality of apple trees. <em>Toprak Bilimi ve Bitki Besleme Dergisi</em> 3(2): 64&ndash;68. [in Turkish].</p>

<p>G&uuml;lser, F., Togay, Y., Togay, N., 2004. The effects of zinc application on zinc efficiency and nutrient composition of lentil (Lens culinaris Medic.) cultivars. <em>Pakistan Journal of Biological Sciences</em> 7(5): 751&ndash;759.</p>

<p>G&uuml;lser, F., Yavuz, H.İ., G&ouml;kkaya, T.H., Sedef, M., 2019. Effects of iron sources and doses on plant growth criteria in soybean seedlings. <em>Eurasian Journal of Soil Science</em> 8(4): 298&ndash;303.</p>

<p>Gyana, R.R., Sunita, S., 2015. Role of iron in plant growth and metabolism. <em>Reviews in Agricultural Science</em> 3: 1&ndash;24.</p>

<p>Hamzah Saleem, M., Usman, K., Rizwan, M., Al Jabri, H., Alsafran, M., 2022. Functions and strategies for enhancing zinc availability in plants for sustainable agriculture. <em>Frontiers in Plant Science</em> 13: 1033092.</p>

<p>Hazelton, P., Murphy, B., 2007. Interpreting Soil Test Results: What Do All the Numbers Mean? CSIRO Publishing, Clayton, Australia. 152p.</p>

<p>Hochmuth, G., 2011. Iron (Fe) nutrition of plants. EDIS SL353/SS555. University of Florida Institute of Food and Agricultural Sciences, Gainesville, Florida, USA.</p>

<p>Imtiaz, M., Rashid, A., Khan, P., Memon, M.Y., Aslam, M., 2010. The role of micronutrients in crop production and human health. <em>Pakistan Journal of Botany</em> 42(4): 2565&ndash;2578.</p>

<p>Iyengar, S.S., Martens, D.C., Miller, W.P., 1981. Distribution and plant availability of soil zinc fractions. <em>Soil Science Society of America Journal</em> 45(4): 735&ndash;739.</p>

<p>Kacar, B., 1994. Chemical analysis of plant and soil analysis. Ankara University Agricultural Faculty Publi,cations No. 3 Ankara, T&uuml;rkiye. [in Turkish].</p>

<p>Lindsay, W.L., Norvell, W.A., 1978. Development of a DTPA soil test for zinc, iron, manganese, and copper. <em>Soil Science Society of America Journal</em> 42(3): 421&ndash;428.</p>

<p>Malakouti, M.J., 2007. Zinc is a neglected element in the life cycle of plants: A review. <em>Middle Eastern and Russian Journal of Plant Science and Biotechnology </em>1: 1&ndash;12.</p>

<p>Marschner, H., 1995. Mineral Nutrition of Higher Plants. 2nd edition. Academic Press, London, UK.</p>

<p>Monreal, C.M., DeRosa, M., Mallubhotla, S.C., Bindraban, P.S., Dimkpa, C., 2016. Nanotechnologies for increasing the crop use efficiency of fertilizer-micronutrients. <em>Biology and Fertility of Soils</em> 52: 423&ndash;437.</p>

<p>Norvell, W.A., Lindsay, W.L., 1972. Reactions of DTPA chelates of iron, zinc, copper, and manganese with soils. <em>Soil Science Society of America Journal</em> 36(5): 778&ndash;783.</p>

<p>Nunes, M.R., Karlen, D.L., Moorman, T.B., Cambardella, C.A., 2020. How does tillage intensity affect chemical soil health indicators? A United States meta-analysis. <em>Agrosystems, Geosciences &amp; Environment</em> 3(1): e20083.</p>

<p>Oliver, M.A., Gregory, P.J., 2015. Soil, food security and human health: A review. <em>European Journal of Soil Science</em> 66: 257&ndash;276.</p>

<p>Paz-Gonz&aacute;lez, A., Vieira, S.R., Castro, M.T.T., 2000. The effect of cultivation on the spatial variability of selected properties of an umbric horizon. <em>Geoderma</em> 97(3&ndash;4): 273&ndash;292.</p>

<p>Petersen, R.G., Calvin, L.D., 1965. Sampling. In: Methods of Soil Analysis: Part 1 Physical and Mineralogical Properties, Including Statistics of Measurement and Sampling, 9.1. Black, C.A. (Ed.). Agronomy Monograph No. 9. American Society of Agronomy, Madison, Wisconsin, USA, pp. 54&ndash;72.</p>

<p>R&ouml;ver, M., Kaiser, E.A., 1999. Spatial heterogeneity within the plough layer: Low and moderate variability of soil properties. <em>Soil Biology and Biochemistry</em> 31(2): 175&ndash;187.</p>

<p>Samra, J.S., Singh, V.P., Sharma, K.N.S., 1988. Analysis of spatial variability in sodic soils. II. Point and block kriging. <em>Soil Science</em> 145: 250&ndash;256.</p>

<p>Shukla, A.K., Behera, S.K., Lenka, N.K., Tiwari, P.K., Prakash, C., Malik, R.S., Sinha, N.K., Singh, V.K., Patra, A.K., Chaudhary, S.K., 2016. Spatial variability of soil micronutrients in the intensively cultivated Trans-Gangetic Plains of India. <em>Soil and Tillage Research</em> 163: 282&ndash;289.</p>

<p>Shuman, L.M., Hargrove, W.L., 1985. Effect of tillage on the distribution of manganese, copper, iron, and zinc in soil fractions. <em>Soil Science Society of America Journal</em> 49(5): 1117&ndash;1121.</p>

<p>Sidsel, B.S., S&oslash;ren, H., 2019. The biochemical properties of manganese in plants. <em>Plants</em> 8(10): 381.</p>

<p>Singh, J.P., Karamanos, R.E., Kachanoski, R.G., 1985. Spatial variation of extractable micronutrients in a cultivated and a native prairie soil. <em>Canadian Journal of Soil Science</em> 65(1): 149&ndash;156.</p>

<p>Tabi, F.O., Ogunkunle, A.O., 2007. Spatial variation of some soil physico-chemical properties of an Alfisol in southwestern Nigeria. <em>Nigerian Journal of Soil and Environmental Research</em> 7: 82&ndash;91.</p>

<p>Tanji, K.K., 1995. Agricultural Salinity Assessment and Management. Scientific Publishers, New York, USA. 619p.</p>

<p>Thapa, S., Bhandari, A., Ghimire, R., Xue, Q., Kidwaro, F., Ghatrehsamani, S., Maharjan, B., Goodwin, M., 2021. Managing micronutrients for improving soil fertility, health, and soybean yield. <em>Sustainability</em> 13(21): 11766.</p>

<p>Trangmar, B.B., Yost, R.S., Uehara, G., 1985. Application of geostatistics to spatial studies of soil properties. <em>Advances in Agronomy</em> 38: 45&ndash;94.</p>

<p>Wang, S., Xu, L., Hao, M., 2022. Impacts of long-term micronutrient fertilizer application on soil properties and micronutrient availability. <em>International Journal of Environmental Research and Public Health</em> 19(23): 16358.</p>

<p>Wei, X., Hao, M., Shao, M., Gale, W.J., 2006. Changes in soil properties and the availability of soil micronutrients after 18 years of cropping and fertilization. <em>Soil and Tillage Research</em> 91(1&ndash;2): 120&ndash;130.</p>

<p>Zhang, R., Rahman, S., Vance, G.F., Munn, L.C., 1995. Geostatistical analyses of trace elements in soils and plants. <em>Soil Science</em> 159(6): 383&ndash;390.</p>

<p>Zhao, Y., Xu, X., Darilek, J.L., Huang, B., Sun, W., Shi, X., 2009. Spatial variability assessment of soil nutrients in an intense agricultural area: A case study of Rugao County in Yangtze River Delta Region, China. <em>Environmental Geology</em> 57(5): 1089&ndash;1102.</p>

<p>Zheng, H., Wu, J., Zhang, S., 2009. Study on the spatial variability of farmland soil nutrient based on the kriging ınterpolation. AICI, International Conference on Artificial Intelligence and Computational Intelligence, Nowember 7-8, Shanghai, China, Vol:4, p. 550-555.</p>

Abstract

This study investigated the spatial variability of DTPA-extractable Fe, Mn, Zn, and Cu in a cultivated field, their relationships with selected soil properties, and the optimum number of samples required to estimate mean micronutrient concentrations precisely. Forty-nine soil samples were collected at 5-m intervals from a square grid within a 30 × 30 m cultivated plot. Mean DTPA-extractable concentrations were 71.80 mg kg⁻¹ for Fe, 350.26 mg kg⁻¹ for Mn, 2.58 mg kg⁻¹ for Zn, and 4.11 mg kg⁻¹ for Cu. The coefficients of variation were higher for Fe (20.6%) and Zn (19.2%) than for Mn (11.8%) and Cu (8.4%). Spatial variability was best described by spherical models for Fe and Mn and exponential models for Zn and Cu. The spatial correlation ranges followed the order Zn (67 m) > Cu (17 m) > Fe (15 m) > Mn (8 m). Nugget-to-sill ratios indicated strong spatial dependence for Fe (0.039%), Mn (8.03%), and Cu (11.32%) and moderate spatial dependence for Zn (42.86%). In principal component analysis, Fe, Cu, and soil organic matter (OM) had high negative loadings on PC1, whereas Zn contributed most strongly to PC2. Fe was positively correlated with soil OM and negatively correlated with Mn, Zn, pH, Ca, and Na. Mn was positively correlated with Zn and Cu, whereas Zn was positively correlated with silt and pH. Cu was negatively correlated with pH, Ca, Mg, and K. The numbers of samples required to estimate mean concentrations within allowable errors of 5%, 10%, and 20% followed the order Fe (69, 17, and 4) > Zn (59, 15, and 4) > Mn (23, 6, and 2) > Cu (11, 3, and 1), respectively. Thus, greater spatial variability in a micronutrient requires a larger sample size to estimate its field mean precisely.

Keywords: Soil properties, Fe, Mn, Zn, Cu, spatial dependence, sampling intensity.

References

Aşkın, T., Kızılkaya, R., 2006. Assessing spatial variability of soil enzyme activities in pasture topsoils using geostatistics. European Journal of Soil Biology 42(4): 230–237.

Aşkın, T., Türkmen, F., Tarakçıoğlu, C., Kulaç, S., Aygün, S., 2017. DTPA-extractable micronutrients: A geostatistical study from Ordu, Turkey. Eurasian Journal of Soil Science 6(2): 154–160.

Behera, S.K., Shukla, A.K., 2014. Total and extractable manganese and iron in some cultivated acid soils of India: Status, distribution and relationship with some soil properties. Pedosphere 24(2): 196–208.

Bo, S., Shenglu, Z., Qiguo, Z., 2003. Evaluation of spatial and temporal changes of soil quality based on geostatistical analysis in the hill region of subtropical China. Geoderma 115: 85–99.

Burrough, P.A., 1993. Fractals and geostatistical methods in landscape studies. In: Fractals in Geography. Lam, N., De Cola, L. (Eds.). Prentice Hall, Englewood Cliffs, NJ, USA, pp. 87–112.

Buttar, T.S., Sharma, V., 2023. Spatial variability of soil micronutrients under paddy (Oryza sativa)-wheat (Triticum aestivum) cropping system in irrigated plains. Indian Journal of Agricultural Sciences 93(4): 403–408.

Cambardella, C.A., Moorman, T.B., Novak, J.M., Parkin, T.B., Karlen, D.L., Turco, R.F., Konopka, A.E., 1994. Field-scale variability of soil properties in central Iowa soils. Soil Science Society of America Journal 58: 1501–1511.

Cameron, D.R., Nyborg, M., Toogood, J.A., Laverty, D.H., 1971. Accuracy of field sampling for soil tests. Canadian Journal of Soil Science 51(2): 165–175.

Chukwu, E.C., Gülser, C., 2025. Morphological, physiological, and anatomical effects of heavy metals on soil and plant health and possible remediation technologies. Soil Security 18: 100178.

Çelim, S., Gülser, F., 2020. The changes caused by different ıron forms in growth of bean (Phaseoulus vulgaris L. Var Nana) under cadmium stress. ISPEC Journal of Agricultural Sciences 4(4): 1006–1023.

de Santiago, A., Quintero, J.M., Delgado, A., 2008. Long-term effects of tillage on the availability of iron, copper, manganese, and zinc in a Spanish Vertisol. Soil and Tillage Research 98(2): 200–207.

Demiralay, I., 1993. Soil physical analysis. Ataturk University Agricultural Faculty Publi,cations No. 143, Erzurum, Türkiye. [in Turkish].

Demirkaya, S., Gülser, C., 2023. Effect of acidified biochar applications on DTPA extractable microelement content in a coarse textured soil. Toprak Bilimi ve Bitki Besleme Dergisi 11(1): 47–53. [in Turkish].

Dhaliwal, S.S., Naresh, R.K., Mandal, A., Walia, M.K., Gupta, R.K., Singh, R., Dhaliwal, M.K., 2019. Effect of manures and fertilizers on soil physical properties, build-up of macro and micronutrients and uptake in soil under different cropping systems: A review. Journal of Plant Nutrition 42(20): 2873–2900.

Dhaliwal, S.S., Sharma, V., Kaur, J., Shukla, A.K., Hossain, A., Abdel-Hafez, S.H., Singh, V.K., 2021. The pedospheric variation of DTPA-extractable Zn, Fe, Mn, Cu and other physicochemical characteristics in major soil orders in existing land use systems of Punjab, India. Sustainability 14(1): 29.

Gamma Design Software, 2010. GS+ Version 9: Geostatistical Software for the Environmental Sciences. Gamma Design Software LLC, Plainwell, Michigan, USA.

Guang, C., Jia, L., Huimin, H., Ruiying, D., Xu, W., 2022. Physiological and molecular mechanisms of plant responses to copper stress. International Journal of Molecular Sciences 23(21): 12950.

Gülser, C., 2023. Effect of soil tillage on soil organic matter in a clay field. Agricultural Sciences 15(38): 1-11.

Gülser, C., Ekberli, İ., Candemir, F., 2016. Spatial variability of soil physical properties in a cultivated field. Eurasian Journal of Soil Science 5(3): 192–200.

Gülser, F., Karaçal, İ., 2015. Comparing the effects of organic and inorganic compounds of iron and zinc on fruit quality of apple trees. Toprak Bilimi ve Bitki Besleme Dergisi 3(2): 64–68. [in Turkish].

Gülser, F., Togay, Y., Togay, N., 2004. The effects of zinc application on zinc efficiency and nutrient composition of lentil (Lens culinaris Medic.) cultivars. Pakistan Journal of Biological Sciences 7(5): 751–759.

Gülser, F., Yavuz, H.İ., Gökkaya, T.H., Sedef, M., 2019. Effects of iron sources and doses on plant growth criteria in soybean seedlings. Eurasian Journal of Soil Science 8(4): 298–303.

Gyana, R.R., Sunita, S., 2015. Role of iron in plant growth and metabolism. Reviews in Agricultural Science 3: 1–24.

Hamzah Saleem, M., Usman, K., Rizwan, M., Al Jabri, H., Alsafran, M., 2022. Functions and strategies for enhancing zinc availability in plants for sustainable agriculture. Frontiers in Plant Science 13: 1033092.

Hazelton, P., Murphy, B., 2007. Interpreting Soil Test Results: What Do All the Numbers Mean? CSIRO Publishing, Clayton, Australia. 152p.

Hochmuth, G., 2011. Iron (Fe) nutrition of plants. EDIS SL353/SS555. University of Florida Institute of Food and Agricultural Sciences, Gainesville, Florida, USA.

Imtiaz, M., Rashid, A., Khan, P., Memon, M.Y., Aslam, M., 2010. The role of micronutrients in crop production and human health. Pakistan Journal of Botany 42(4): 2565–2578.

Iyengar, S.S., Martens, D.C., Miller, W.P., 1981. Distribution and plant availability of soil zinc fractions. Soil Science Society of America Journal 45(4): 735–739.

Kacar, B., 1994. Chemical analysis of plant and soil analysis. Ankara University Agricultural Faculty Publi,cations No. 3 Ankara, Türkiye. [in Turkish].

Lindsay, W.L., Norvell, W.A., 1978. Development of a DTPA soil test for zinc, iron, manganese, and copper. Soil Science Society of America Journal 42(3): 421–428.

Malakouti, M.J., 2007. Zinc is a neglected element in the life cycle of plants: A review. Middle Eastern and Russian Journal of Plant Science and Biotechnology 1: 1–12.

Marschner, H., 1995. Mineral Nutrition of Higher Plants. 2nd edition. Academic Press, London, UK.

Monreal, C.M., DeRosa, M., Mallubhotla, S.C., Bindraban, P.S., Dimkpa, C., 2016. Nanotechnologies for increasing the crop use efficiency of fertilizer-micronutrients. Biology and Fertility of Soils 52: 423–437.

Norvell, W.A., Lindsay, W.L., 1972. Reactions of DTPA chelates of iron, zinc, copper, and manganese with soils. Soil Science Society of America Journal 36(5): 778–783.

Nunes, M.R., Karlen, D.L., Moorman, T.B., Cambardella, C.A., 2020. How does tillage intensity affect chemical soil health indicators? A United States meta-analysis. Agrosystems, Geosciences & Environment 3(1): e20083.

Oliver, M.A., Gregory, P.J., 2015. Soil, food security and human health: A review. European Journal of Soil Science 66: 257–276.

Paz-González, A., Vieira, S.R., Castro, M.T.T., 2000. The effect of cultivation on the spatial variability of selected properties of an umbric horizon. Geoderma 97(3–4): 273–292.

Petersen, R.G., Calvin, L.D., 1965. Sampling. In: Methods of Soil Analysis: Part 1 Physical and Mineralogical Properties, Including Statistics of Measurement and Sampling, 9.1. Black, C.A. (Ed.). Agronomy Monograph No. 9. American Society of Agronomy, Madison, Wisconsin, USA, pp. 54–72.

Röver, M., Kaiser, E.A., 1999. Spatial heterogeneity within the plough layer: Low and moderate variability of soil properties. Soil Biology and Biochemistry 31(2): 175–187.

Samra, J.S., Singh, V.P., Sharma, K.N.S., 1988. Analysis of spatial variability in sodic soils. II. Point and block kriging. Soil Science 145: 250–256.

Shukla, A.K., Behera, S.K., Lenka, N.K., Tiwari, P.K., Prakash, C., Malik, R.S., Sinha, N.K., Singh, V.K., Patra, A.K., Chaudhary, S.K., 2016. Spatial variability of soil micronutrients in the intensively cultivated Trans-Gangetic Plains of India. Soil and Tillage Research 163: 282–289.

Shuman, L.M., Hargrove, W.L., 1985. Effect of tillage on the distribution of manganese, copper, iron, and zinc in soil fractions. Soil Science Society of America Journal 49(5): 1117–1121.

Sidsel, B.S., Søren, H., 2019. The biochemical properties of manganese in plants. Plants 8(10): 381.

Singh, J.P., Karamanos, R.E., Kachanoski, R.G., 1985. Spatial variation of extractable micronutrients in a cultivated and a native prairie soil. Canadian Journal of Soil Science 65(1): 149–156.

Tabi, F.O., Ogunkunle, A.O., 2007. Spatial variation of some soil physico-chemical properties of an Alfisol in southwestern Nigeria. Nigerian Journal of Soil and Environmental Research 7: 82–91.

Tanji, K.K., 1995. Agricultural Salinity Assessment and Management. Scientific Publishers, New York, USA. 619p.

Thapa, S., Bhandari, A., Ghimire, R., Xue, Q., Kidwaro, F., Ghatrehsamani, S., Maharjan, B., Goodwin, M., 2021. Managing micronutrients for improving soil fertility, health, and soybean yield. Sustainability 13(21): 11766.

Trangmar, B.B., Yost, R.S., Uehara, G., 1985. Application of geostatistics to spatial studies of soil properties. Advances in Agronomy 38: 45–94.

Wang, S., Xu, L., Hao, M., 2022. Impacts of long-term micronutrient fertilizer application on soil properties and micronutrient availability. International Journal of Environmental Research and Public Health 19(23): 16358.

Wei, X., Hao, M., Shao, M., Gale, W.J., 2006. Changes in soil properties and the availability of soil micronutrients after 18 years of cropping and fertilization. Soil and Tillage Research 91(1–2): 120–130.

Zhang, R., Rahman, S., Vance, G.F., Munn, L.C., 1995. Geostatistical analyses of trace elements in soils and plants. Soil Science 159(6): 383–390.

Zhao, Y., Xu, X., Darilek, J.L., Huang, B., Sun, W., Shi, X., 2009. Spatial variability assessment of soil nutrients in an intense agricultural area: A case study of Rugao County in Yangtze River Delta Region, China. Environmental Geology 57(5): 1089–1102.

Zheng, H., Wu, J., Zhang, S., 2009. Study on the spatial variability of farmland soil nutrient based on the kriging ınterpolation. AICI, International Conference on Artificial Intelligence and Computational Intelligence, Nowember 7-8, Shanghai, China, Vol:4, p. 550-555.