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RESEARCH ARTICLE

Changes in Clay Mineral Composition and Soil Potassium Pools Under 50 Years of Soybean–Wheat Cropping in an Alfisol

Harshit Aman

Harshit Aman

Soil Technology and Carbon Sequestration Laboratory, Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India

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Amlan Kumar Ghosh

Corresponding Author

Amlan Kumar Ghosh

Soil Technology and Carbon Sequestration Laboratory, Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India

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Dibyajyoti Panda

Dibyajyoti Panda

Soil Technology and Carbon Sequestration Laboratory, Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India

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Chandni Pradhan

Chandni Pradhan

Soil Technology and Carbon Sequestration Laboratory, Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India

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Prabhakar Mahapatra

Prabhakar Mahapatra

Department of Soil Science and Agricultural Chemistry, Birsa Agricultural University, Ranchi, Jharkhand, India

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Ranjan Paul

Ranjan Paul

National Bureau of Soil Survey and Land Use Planning, Nagpur, Maharashtra, India

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Gopal Tiwari

Gopal Tiwari

National Bureau of Soil Survey and Land Use Planning, Nagpur, Maharashtra, India

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First published: 26 June 2025

Academic editor: Mark Wuddivira.

Funding: This research was supported by the IoE grant of the Banaras Hindu University of 2022–23 (46736).

ABSTRACT

Background

Potassium fertilizers are imported in India, and hence, potassium fertilization is a costly input. Resource poor cultivators variably use potassium fertilization for crop production which disturbs potassium dynamics in soil impacting soil health.

Aim

A long-term negative potassium balance in the cropping system can result in the release of potassium from the non-exchangeable pool, ultimately resulting in changes in clay mineralogy, amounting to chemical degradation of soil.

Method

Soils from a long-term soybean–wheat cropping system receiving variable amounts of potassium fertilizers, which was in the 50th cropping cycle, were used to investigate the potassium pools and clay mineralogy.

Result

There was considerable reduction in yield both in control (78.7%) and 100% NP treatments (15.95%). The negative K balance followed the order 100% NP > 100% NPK > 50% NPK > 150% NPK. To meet the potassium requirement and negative potassium balances, potassium was being released from interlayers resulting in the annual loss of non-exchangeable K up to 2.42, 1.06, 0.74, and 1.34 kg ha−1 year−1 under 100% NP, Control, 50% NPK, and 100% NPK, respectively. The 100% NP treatment showed the smallest intensity of illite followed by 100% NPK, 50% NPK, Control, and 150% NPK. The illite intensity was reduced by 41.6%, 11.7%, 8.49%, and 1.6% in the 100% NP, 100% NPK, 50% NPK, and Control treatments, respectively, compared to 150% NPK.

Conclusion

The correlation studies revealed a positive association between negative balance, non-exchangeable K, and illite, supporting the hypothesis that a reduction in non-exchangeable K under negative K balances results in alterations in the clay mineralogical composition.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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