Soil Aggregate Formation and Stability Induced By Application of Biochar Derived from Anaerobic Digestion Effluent.

Soil aggregates play major roles for sound physicochemical and biological functions of soils. Soils near Guanajuato, Mexico suffer from poor soil physical properties such as low infiltration and poor aeration. One of soil additives to improve soil physical properties is biochars (BC) by increasing soil aggregates when applied in soils. Since one of major industries in Guanajuato is meat production releasing daily 2 million L of wastewater, anaerobic digestion effluents (ADEs) after anaerobically treating wastewater from slaughter houses could be a useful material for producing biochars. Therefore, objective of this study was to evaluate soil aggregate formation and stability induced by application of biochar derived from ADE from slaughter house near Guanajuato.

               Soils used in this study were Vertisol and Phaoezem collected from near Guanajuato. Biochars were derived from solid part of ADE and pyrolysed at 550^oC and 800^oC (BC550 and BC800, respectively) with 37.2% and 16.4% of volatile matter (VM) content, respectively. Both soils without or with BC (1% w/w) were incubated at 30^oC with 50% of water holding capacity. Cumulative soil respiration, aggregate size distribution, and aggregate mean weight diameter (MDW) were analyzed.

               Cumulative respiration rates in both soils with BC550 and BC800 rapidly increased during first 16 d of incubation, however those with BC550 were significantly greater than those with BC800 for both soils. Increases in macro-aggregate and MWD caused by BC application were greater with BC550 than with BC800. Positive correlations between the initial slope of cumulative soil respiration rates and MWD increases were observed for both soils because greater VM content in BC550 may have caused greater soil respiration rates and MWD than BC800.