Soil-Test biological activity with short- and long-term carbon contributions

Authors: Franzluebbers, Alan; SIMIONI ASSMANN, TANGRIANI - Federal University Of Technology - Parana

Submitted to: Agricultural and Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2020
Publication Date: 10/19/2020
Citation: Franzluebbers, A.J., Simioni Assmann, T. 2020. Soil-Test biological activity with short- and long-term carbon contributions. Agricultural and Environmental Letters. 5, Article 20035.

Interpretive Summary: Living soil breathes! This life can be detected from the carbon dioxide emitted from soil through the actions of soil microorganisms decomposing organic matter. Interest in determining soil biological activity is growing, because of soil health enthusiasm by farmers and various stakeholders devoted to regenerative agriculture. An ARS scientist in Raleigh North Carolina collaborated with a visiting scientist from the Federal Technical University of Parana in Brazil to test how much soil-test biological activity changes in response to sampling during a growing crop. Short-term effect of root development in soil was relatively minor (7%) compared with much greater long-term effects from edaphic factors promoted by long-term management (81%). Results indicate that short-term changes in soil-test biological activity are important, but modest compared with variations due to edaphic factors of soil depth and texture. These results will help users of soil-health testing to understand the extent of soil biological changes that can be expected during different sampling periods within the year.

Technical Abstract: Soil-test biological activity is a key indicator of soil health, because of its relevance to ecosystem processing, broad applicability across diverse environments, simple methodology, and rapid analysis time. We assessed the relative contribution of short-term and long-term influences of C availability on soil-test biological activity. A short-term factor was from soil exposed to different lengths of time to sudangrass (Sorghum x drummondii) test crop grown under greenhouse conditions in small mesocosms. Long-term factors were from 16 years of a field study varying in pasture-crop rotation system, soil depth, and texture. Soil-test biological activity was determined from the flush of CO2 during 3 days following rewetting of dried soil, which varied 7% from short-term influences and 81% from long-term influences. Soil depth was the primary long-term factor influencing soil-test biological activity (57%) and soil texture was intermediate (24%). Soil-test biological activity was highly associated with soil N mineralization and soil microbial biomass C, as well as with greenhouse growth of the sudangrass test crop and its total N uptake. As a proportion of antecedent long-term field conditions during the winter, soil-test biological activity increased 53 + 25% at different lengths of time (14, 21, 31, and 45 days) following growth of sudangrass in the greenhouse. Results indicate that short-term changes in soil-test biological activity are important, but modest compared with variations due to edaphic factors of soil depth and texture.