Multiple Microbial Activity-Based Measures Reflect Effects of Cover Cropping and Tillage on Soils.

Agricultural producers, conservation professionals, and policy makers are eager to learn of soil analytical techniques and data that document improvement in soil health by agricultural practices such as no-till and incorporation of cover crops. However, there is considerable uncertainty within the research community regarding the appropriate methods to actually measure soil health. We evaluated the effect of tillage (no-till vs. conventional till) and cover crop (plus or minus) treatments on soil microorganisms using five different activity-based measurements. A low-growing cover crop mix was inter-seeded into a corn/soybean rotation (replicated field plots) so that the ground was never barren of a living plant. Soil samples were collected in the fall following cash crop harvest in 2014 and 2015. We measured substrate-induced respiration (SIR) with glucose and phenol using disaggregated soils and intact minicores, fluorescein diacetate hydrolysis (FDA), flush of CO2 upon wetting dried soil, and potentially-mineralizable N. Respiration-based approaches distinguished cover crop and tillage effects, although there were interactions with crop phase for some measures. Both measures of SIR (disaggregated and intact soils) reflected higher activities with cover crops and no-till. The SIR response to the different substrates (glucose, phenol) varied according to crop phase. Potentially-mineralizable N was sensitive to treatments; however, FDA hydrolysis was not. Our results identify measures which are effective at detecting management effects on soil microbial activities, and also provide evidence for the benefits of combining practices such as no-till and cover cropping.