The use of biochar for recovery of excess nutrients in dairy manure effluent and the use of nutrient-enriched biochar as soil amendment can offer a robust solution for multiple environmental issues. In this study we determined the capacity of biochar, produced by pyrolyzing mixed hardwood feedstock at 300°C, to adsorb and retain or release two major nutrient ions: ammonium (NH) and phosphate (PO). We conducted the experiment using a range of nutrient concentrations that represent those commonly observed in dairy manure effluent (0-50 mg L for PO and 0-1000 mg L for NH). Up to 5.3 mg g NH and 0.24 mg g PO was adsorbed from manure by biochar (18 and 50% of total amount in the manure slurry, respectively). During the desorption phase of the experiment, biochar retained 78 to 91% of the sorbed NH and 60% of the sorbed PO at reaction times <24 h. Our findings confirm that biochar can be used for recovering excess nitrogen and phosphorus from agricultural water, such as dairy manure effluent.

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Amending soils with biochar can have multiple environmental benefits, including improvement in soil physicochemical properties, carbon sequestration, reduction in leaching losses of essential nutrients, and reduction in greenhouse gas (GHG) emissions. This study was conducted to determine the effect of enriched biochar amendments on leaching losses of essential nutrients and GHG emissions from soil. The enriched biochar was prepared by shaking biochar with dairy manure effluent for 24 h, which increased the C and N concentration of biochar by 9.3 and 8.3%, respectively. Incubation and leaching experiments were conducted for 8 wk with three treatments: soil, soil + 1% biochar, and soil + 1% enriched biochar. Amendment with biochar and enriched biochar relative to unamended soil resulted in 68 and 75% reduction in net nitrification, 221 and 229% reduction in net ammonification, 67 and 68% reduction in cumulative CO flux, respectively, and 26% reduction in cumulative NO flux for both biochar treatments. There were no significant differences among treatments in total leaching losses of C, N, and base cations. Our findings suggest that enrichment of biochar with dairy manure effluent can promote C and N storage in soil and provide additional environmental benefits.

Physical protection of C by aggregates and their response to forest management are important components of soil C management. This study was conducted to examine the morphology and strength of aggregates, to quantify C held by aggregates, and to study the effects of forest management intensity on aggregation. Surface horizon soil (0–5‐ and 5–10‐cm depths) was collected from a 4‐yr‐old loblolly pine (Pinus taeda L.) plantation in North Florida under two contrasting management regimes (intensive vs. operational fertilization and chemical weed control, called high‐ and low‐intensity treatments, respectively). Samples were dry sieved into four size classes: 2000 to 250, 250 to 150, 150 to 53, and <53 μm. Soil aggregates of varying morphology and strength were observed in the three sand size fractions. Aggregate strength, as measured by sonication, varied with size fraction and ranged from approximately 17 J mL−1 for the least stable macroaggregates in the 2000‐ to 250‐μm fraction to 113 J mL−1 for the most stable microaggregates in the 150‐ to 53‐μm fraction. Aggregate organic matter (AOM) was an important C pool in these soils, accounting for nearly half of the total soil organic matter. The high‐intensity management treatment had lower AOM in the 2000‐ to 250‐μm fraction, probably due to lower biomass input of understory roots caused by chemical understory control. Modification of the sonication technique proved useful for studying different aspects of aggregation and gave indications of an aggregate hierarchy even in these extremely sandy soils.

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