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ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #319618
Title: Impact of switchgrass biochars with supplemental nitrogen on carbon-nitrogen mineralization in highly weathered Coastal Plain Ultisols

Author
item Sigua, Gilbert
item Novak, Jeffrey
item Watts, Donald - Don
item Szogi, Ariel
item Shumaker, Paul

Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2015
Publication Date: 12/11/2015
Citation: Sigua, G.C., Novak, J.M., Watts, D.W., Szogi, A.A., Shumaker, P.D. 2015. Impact of switchgrass biochars with supplemental nitrogen on carbon-nitrogen mineralization in highly weathered Coastal Plain Ultisols. Chemosphere. 145:135-141.

Interpretive Summary: The use of biochars has gained widespread attention as a potential amendment to boost soil fertility. However, there is still a need to pursue additional research that will improve our understanding on the impact of soil fertility enhancement because the effect may vary greatly between switchgrass (Panicum virgatum, L) residues (USG) and switchgrass biochars (SG). We hypothesized that SG with supplemental nitrogen (N) would deliver more positive effects on carbon (C) and N mineralization than USG. The objective of this study was to evaluate the effects of USG and SG, with or without supplemental inorganic N fertilizer on C and N mineralization in highly weathered Coastal Plain Ultisols. The application rate for SG and USG based on a corn yield goal of 112 kilogram (kg)/ha was 40 megagram (Mg)/ha. Inorganic N was added at the rate of 100 kg N/ha, also based on a corn yield of 112 kg/ha. Experimental treatments were: control (CONT) soil; control with N (CONT+N); switchgrass residues (USG); USG with N (USG+N); switchgrass biochars at 250oC (250SG); SG at 250oC with N (250SG+N); SG at 500oC (500SG); and SG at 500oC with N (500SG+N). In summary, switchgrass biochars and switchgrass residues had contrasting effects on nitrogen mineralization in a highly weathered Ultisol in Coastal Plains region. Cumulative and net carbon dioxide evolution was increased by the additions of SG and USG especially when supplemented with N. Soils treated with 250SG had the least amount of total inorganix nitrogen (TIN) while the greatest amount of TIN was observed from the CONT+N. Results suggest that application of SG in the short term may cause N immobilization resulting in the reduction of TIN. Our research demonstrates that care has to be taken when applying biochar because it could affect crop growth and productivity as a result of potential N immobilization. Biochar application might in some cases require a supplemental N fertilization to avoid crop growth retardation. As a precautionary measure, there is a need to consider applying biochar some months before the main crop season starts to avoid negative effects of N immobilization on crop performance.

Technical Abstract: Although an increase in soil fertility is the most frequently reported benefit linked to adding biochar to soils, there is still a need to pursue additional research that will improve our understanding on the impact of soil fertility enhancement because the effect could vary greatly between switchgrass (Panicum virgatum, L) residues (USG) and switchgrass biochars (SG). We hypothesized that SG with supplemental nitrogen (N) would deliver more positive effects on carbon (C) and N mineralization than USG. The objective of this study was to evaluate the effects of USG and SG, with or without supplemental inorganic N fertilizer on C and N mineralization in highly weathered Coastal Plain Ultisols. The application rate for SG and USG based on a corn yield goal of 112 kilogram (kg)/ha was 40 megagrams (Mg)/ha. Inorganic N was added at the rate of 100 kg N/ha, also based on a corn yield of 112 kg/ha. Experimental treatments were: control (CONT) soil; control with N (CONT+N); switchgrass residues (USG); USG with N (USG+N); switchgrass biochars at 250oC (250SG); SG at 250oC with N (250SG+N); SG at 500oC (500SG); and SG at 500oC with N (500SG+N). Cumulative and net carbon dioxide evolution was increased by the additions of SG and USG especially when supplemented with N. Soils treated with 250SG (8.6 milligram (mg)/kg) had the least concentration of TIN while the greatest amount of TIN was observed from the CONT+N (19.0 mg/kg). Our results suggest that application of SG in the short term may cause N immobilization resulting in the reduction of TIN.