Wildfi re-produced charcoal is a common component of soils, affecting a range of important abiotic and biotic soil processes. Our ability to predict the effects of charcoal addition to soil is currently limited, however, by our understanding of how charcoal affects the soil microbial community mediating many of these processes. This study sought to improve our understanding of the relationship between charcoal addition and soil microbial biomass and activity among temperate soils. Charcoal was added to four distinct temperate soils, a Mollisol, an Alfi sol, an Entisol, and a Spodosol, at fi ve application levels ranging from 0 to 0.1 kg charcoal kg −1 soil, and incubated at 25°C with measurements at approximately 0, 1.5, and 3 mo. We hypothesized that microbial biomass and activity would increase with increasing charcoal application in all soils, but the relative magnitude of the response would depend on the texture and fertility of each soil. As hypothesized, microbial biomass and activity and Bray P increased signifi cantly with increasing charcoal application, while extractable N decreased. The coniferous forest soil provided a notable exception to the general patterns of N availability, having the highest total extractable N at the highest charcoal application level. Our results suggest that charcoal additions affected microbial biomass, microbial activity, and nutrient availability in relatively similar ways in all four soils that we studied, suggesting considerable predictability in response to charcoal application. Differences in the magnitude of the microbial response, however, appeared dependent on differences in nutrient availability among soils.Abbreviations: BR, basal respiration; DOC, dissolved organic carbon; MQ, metabolic quotient; SIR, substrate-induced respiration.

No abstract

Pesticide mobility through Sparta sand from the Lower Wisconsin River Valley (LWRV) and Plainfield sand from the Central Sands (CS) of Wisconsin was examined to interpret results from state‐sponsored groundwater monitoring programs and to identify fundamental mechanisms important in pesticide transport through the unsaturated zone. The mobility of 14C‐labeled atrazine [2‐chloro‐(4‐ethylamino)‐6‐(isopropylamino)‐s‐triazine], alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxym ethyl) acetamide], and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] was monitored through replicated intact soil column‐microlysimeters. Soil columns of Sparta sand (sandy, mixed, mesic Entic Hapludolls) from the LWRV and Plainfield sand (sandy, mixed, mesic Typic Udipsamments) from the CS were instrumented in the greenhouse to simulate field conditions. All pesticides were shown to be much more mobile through the Sparta sand as compared to Plainfield sand. Peak atrazine concentration was 15 times greater in the leachate from the Sparta soil than from the Plainfield sand. Percentage loss of applied pesticide was four times greater in the leachate from the Sparta soil than from the Plainfield sand. Similar results were found for metolachlor and alachlor. The relative order of mobility for each soil was found to be atrazine > metolachlor > alachlor. Factors found to contribute to increased mobility of pesticides through the Sparta sand include higher hydraulic conductivity, smaller water‐holding capacity, and less atrazine adsorption due to less organic C and clay content. The hydraulic conductivity (Ksat) of the upper motzone (0–20 cm) of the Sparta soil is five times faster than the Plainfield soil. The waterholding capacity and the atrazine adsorption coefficient (Kd) of the Plainfield sand were measured to be 1.6 and 1.8 times greater, respectively, than those of the Sparta soil.

No abstract

To better understand agricultural nutrient losses, we evaluated relationships between management (e.g., manure and tillage), soil health measurements, and resulting edgeof-field (EOF) surface water quality. This work was conducted before or early into conservation implementation at 14 Great Lakes Restoration Initiative EOF sites spanning Wisconsin, Michigan, Indiana, Ohio, and New York. Analyses of site characteristics (hydroclimate, management, catchment properties) along with 3 yr of soil health measurements (chemical, biological, and physical properties) showed EOFnutrient export depended on both site and soil properties. A pattern emerged whereby sites not receiving manure and sites with manure defined opposite ends of several gradients for soil and water data. Sites receiving manure had increased microbial activity, organic matter (3.2 vs. 2.7%), and soil test phosphorus (P) (2.8 times more) relative to sites without manure. Suspended sediments (SS), total P (TP), and total nitrogen (TN) in EOF surface runoff varied over three to five orders. Multivariate analysis among sites showed covariant linkages between soil nutrients, soil C, microbial properties, and nutrients in EOF water. There were positive univariate relationships between water-extractable soil P and annual EOF-water concentrations and yields of orthophosphate, TP, TN, and SS (p < .01). Some soil physical properties (e.g., bulk density and infiltration) also covaried among sites but were not consistently related to runoff index or water yield variables. Given the observed among-site variability, we were not able to isolate desirable soil health signals on EOF surface water quality.