Urease activity and nitrogen dynamics in highly weathered soils with designer biochars under corn cultivation

Authors: Sigua, Gilbert; Novak, Jeffrey; Watts, Donald - Don; Myers, William - Tillman; Ducey, Thomas; Stone, Kenneth

Submitted to: Biochar Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2020
Publication Date: 5/30/2020
Citation: Sigua, G.C., Novak, J.M., Watts, D.W., Myers Jr, W.T., Ducey, T.F., Stone, K.C. 2020. Urease activity and nitrogen dynamics in highly weathered soils with designer biochars under corn cultivation. Biochar Journal. https://doi.org/10.1007/s42773-020-00052-4.
DOI: https://doi.org/10.1007/s42773-020-00052-4

Interpretive Summary: Highly weathered soils in the southeastern Coastal Plain region has several deficiencies related to crop production that includes, low soil organic carbon, poor water retention, poor soil nutrient contents (especially nitrogen), and soil acidity. These soil characteristics may severely limit soil and crop productivity, which leaves few management options for improvements. Designer biochar has been described as a possible means to improve soil quality of highly weathered soils. In our field study, we demonstrated the favorable effects of different designer biochars on enhancing urease activity and nitrogen dynamics of extensively weathered soils. Our results supported our hypothesis that the addition of different designer biochars to a highly weathered soil in the field will have variable effects on improving soil chemical and fertility conditions. Particularly important is our research has provided information to systematically understand biochar-urease-nitrogen interactions over the long term under field condition. Field research is critical to future development of different designer biochars in agricultural markets as fertilizers or organic amendments and for future development of biochar technology. Overall, promising results of applying biochars in highly weathered soils since different designer biochars did enhance urease activity and improve total nitrogen and total inorganic nitrogen of Goldsboro soil series, an extensively weathered soils in Coastal Plain region of the United States. Biochars then could be designed with specific chemical and physical properties to target specific soil deficiencies. Additional research is needed to systematically understand biochar-urease-nitrogen interactions over the long term under field condition.

Technical Abstract: Application of designer biochar has the potential to impact soil enzyme activity and soil nitrogen dynamics. However, very little is known about the mechanisms responsible for biochar-enzyme-nitrogen interaction in highly weathered soils. The objective of our three-year (2016-2018) field experiment was to evaluate the effectiveness of designer biochars (DB) in enhancing urease activity (UA), total nitrogen (TN), total inorganic nitrogen (TIN), and nitrogen uptake (NU) at different growth stages (GS) of corn in a highly weathered soil of southeastern Coastal Plain region, USA. Experimental treatments were consisted of the control, 100% pine chips (100PC), 100 percent (%) poultry litter (100PL), 2:1 blend of PC and PL (PCPL), 100% raw switchgrass (Panicum vaginatum, L; 100RSG), and 2:1 blend of PC and RSG (PCRSG). All treatments were applied at the rate of 30,000 kg ha-1 to a Goldsboro loamy sand in 2016. Urease activity, TN, TIN, and NU varied remarkably with DB (p=0.0001) at different GS (p=0.0001) of corn. Soils treated with 100PL had the greatest UA (28.18 microgram nitrogen per gram per hour (µg N/g/hr), TN (0.087%), and TIN (14.53 milligram per kilogram (mg/kg) while the least UA, TN, and TIN of 20.55 µg N/g/hr, 0.063%, and 5.42 mg/kg, respectively were observed from the control. The three-year TN average increase over the control was in the order: 100PL (36.8%) > 100RSG (25.8) > PCRSG (25.3%) > PCPL (23.9%) > 100PC (7.1%). The greatest NU of corn of 140.4 kilogram N per hectare (kg N/ha) was from soils treated with 100PL while the least amount of NU was from 100PC. Overall, our results showed promising significance for the treatment of a highly weathered soils since application of DB did enhance UA and improve TN and TIN in the soils.