Bentonite-Based Organic Amendment Enriches Microbial Activity in Agricultural Soils

Rahul Datta,Jakub Elbl,Subhan Danish,Ludmila Balakova,Vaclav Pecina,Oldrich Latal,Antonin Kintl,Petr Skarpa,Tomas Vyhnanek,Jiri Holatko,Martin Brtnicky,Muhammad Zafar-Ul-Hye,Tivadar Baltazar,Tereza Hammerschmiedt,Maja Radziemska

doi:10.3390/land9080258

Abstract

Bentonite-based organic amendments may have the potential to enhance soil microbial properties. The experiment was carried out from 2014 to 2017 comprising four treatments: NPK fertilizer (nitrogen, phosphorus and potassium mineral fertilizer as a control), NPK + cattle manure, NPK + bentonite, and NPK + combination of manure with bentonite (MB) to verify this hypothesis. The effect of treatments on seven different soil microbial properties was measured: dehydrogenase activity (DHA), bacterial phospholipid fatty acid content, fungal phospholipid fatty acid content, microbial biomass carbon (Cmic), 16S rDNA, 18S rDNA, and ammonia-oxidizing bacteria in soil. The results showed that solely bentonite treatment increases the bacterial and fungal biomass, which was further confirmed by the increased 16S rDNA and 18s rDNA gene copy numbers. The only significantly decreased values upon treatment with solely bentonite were recorded for DHA and Cmic. The ammonia-oxidizing bacteria population increased with the sole application of bentonite and reached its maximum value when bentonite was applied with manure. The MB treatment showed the highest value for all seven measured properties. In summary, the application of bentonite solely might increase or decrease the soil activity, but its addition, along with manure, always promotes an abundance of soil microorganisms and their activity. The co-application of bentonite with manure altered the soil microbial properties in a 3-year field experiment in favor of increased microbial biomass, which is beneficial for agriculture and environment and reveals the potential for the restoration of polluted lands.

Highlights

Soil erosion is a consequence of unsustainable land management; it leads to increase in land degradation and a decrease in soil fertility, and it directly affects agricultural productivity [1].Inorganic fertilizers are frequently used to increase soil fertility and crop yield
These research findings suggest that the application of solely bentonite or its combination with manure increases fungal and bacterial biomass in comparison with the control variant, as evidenced by the increased values of BPLFA and FPLFA
The increased fungal and bacterial biomass upon the bentonite and manure treatment positively correlates with the 16S rDNA copies and

Summary

Introduction

Inorganic fertilizers are frequently used to increase soil fertility and crop yield. They are not a permanent solution to tackle soil infertility. The long-term application of mineral fertilizers into soils with a low percentage of organic compounds accelerates the mineralization of soil organic matter (SOM) and disrupts the natural metabolic processes of soil organisms. This leads to a reduction in the SOM content, nutritional imbalance, and soil acidification [2]. Natural amendments, such as bentonite and its combination with manure, could be useful tools to maintain or increase the SOM in a sustainable way

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