Long-term impact of single biochar and compost application on soil aggregation

Le résumé fourni par la source

Abstract Soil aggregation is an important indicator of soil quality and highly responsive to management such as application of organic amendments. Compost generally increases aggregate stability and enhances soil microbial activity, while the effects of biochar on these factors remain inconclusive. We investigated the effect of biochar and compost on soil aggregation and microbial abundance at an experimental soil rehabilitation site in Ngaoundéré, Cameroon. Sampling was carried out 3.5 years after installation of the site. Both amendments improved bulk density, hydraulic conductivity, pH, and base saturation. Cation exchange capacity and soil organic matter (SOM) content were rather a function of soil texture than influenced by the amendments. Bacterial abundance increased in the compost, but not in the biochar treatment. Fungi were more frequent in smaller aggregates, but did not respond to the treatments. Macroaggregates 400 – 2,000 µm contributed ca. 75 % of the soil functions assessed. Yet, SOM content was 4 times higher in microaggregates < 50 µm than in macroaggregates throughout all treatments. We conclude that single applications of organic amendments can have positive long-term effects on soil aggregation in undisturbed degraded soils, particularly in the macroaggregate fraction. Microaggregates harbour fungal hyphae and are rich in SOM, independent of amendments.

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