Long-lasting Effects of Bentonite on Properties of A Sandy Soil Deprived of the Humus Layer

Abstract

Bentonite has been recognized as a very good material for the improvement of coarse textured soils. In microplot experiment, of a sandy soil deprived of the humus layer was enriched in 1973 with waste bentonite at the rates of 0, 3, 6 and 12 kg m-2. Until 2002, the microplots were planted with different crops and regularly enriched with mineral and organic fertilizers. Since 2003, the microplots were left barren. In 2009, determinations of several features of the soils (in 5-30, 30-55 and 55-80 cm layers) showed that the historical amendment of the sandy soil with bentonite (especially its highest dose) ensured significantly higher contents of water, organic C, clay, silt and a sand fraction with particle diameter <0.1 mm in 5-30 cm layer. Proportions of non-dispersible clay in the total clay of bentonite soils in the two upper soil layers were significantly lower than those of the control soil. A significant increase in the penetrometer resistance was observed in 40-58 cm layers of the control soil and the soil with 3 kg m-2 bentonite amendment, contrary to the soils with two highest bentonite doses.

The Effect of Bentonite on the Survival of Azotobacter chroococcum in Sandy Soil in a Long-Term Plot Experiment

“…As previously written [10][11][12], the enrichment of the basic soil (which was very poor in mineral colloids and organic matter) with BNT and organic and mineral fertilizers improved some physical (e.g., the increase of water-holding capacity) and some chemical (e.g., the increase of pH and contents of organic C and total N) properties. The exposure of these soils during a further eight years to drastic conditions of bare fallowing without fertilization (when all labile substances were removed from the upper soil layer by decomposition by soil microorganisms or leaching by showers), allowed finding out that highly persistent organic-mineral complexes were formed in the upper layer of BNT-amended soils (especially of the soil with the highest dose of BNT).…”

“…Significantly higher contents of organic carbon, total nitrogen, total manganese, available phosphorus, and water in the soils amended with BNT, especially with its highest dose [10][11][12], could also positively affect Azotobacter's CFU number in those soils. As was presented in several papers, the CFU number of Azotobacter in soils was positively correlated with organic C concentration [13-14, 26, 35-37], total N concentration [13][14]37], total Mn concentration [38], and available phosphorus concentration [38][39].…”

“…Its cation exchange capacity was equal to 26 cmol c kg -1 . The microplot experiment involved 16 plots (0.8 m 2 ) with concrete walls (1 m diameter, 1 m depth), and four replicates for each treatment [11][12]. As the bacteria of the genus Azotobacter were absent in the basic soil and BNT, in 1973 (two months after BNT addition to the soil) the soils were inoculated with Azotobacter chroococcum strain 34B from the collection of the Microbiology Department of the Institute of Soil Science and Plant Cultivation in Puławy.…”

“…The pH of the control soil which was not enriched with BNT had to be regulated by a CaCO 3 addition approximately every four years. Since 2003 the plots were left as bare fallow with no fertilization to find out how stable the organic and mineral soil constituents would be [11][12].…”

Sorption properties of separate granulometric fractions in Haplic Cambisol

“…Soil granulometric composition has great influence on sorption (Skic et al, 2016;Czaban et al, 2014), physical features (Brogowski and Kwasowski, 2015;Brogowski et al, 2014;Rafraf et al, 2016;Malik et al, 2014), biological properties (Stemmer et al, 1998), soil typology (Kozłowski and Komisarek, 2017a, b;Musztyfaga and Kabała, 2015) and determines soil fertility and management (Kalembasa et al, 2011). So far, to recognize the role of grain size, extensive studies were performed on the sorption properties of particular granulometric fractions (Okołowicz, 1996;Asadu et al, 1997) and analysis of surface microstructures to understand the weathering process and formation of sorption properties (Morrás, 1995;Brogowski and Kocoń, 1984).…”