Location: Soil and Water Conservation ResearchTitle: Stratification of soil chemical and microbial properties under no-till management after lime amendment Author
|Barth, Victoria - Washington State University|
|Reardon, Catherine - Kate|
|Coffey, Todd - Washington State University|
|Mcfarland, Carol - Washington State University|
|Sullivan, Tarah - Washington State University|
Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2018
Publication Date: N/A
Interpretive Summary: In the dryland cropping region of the inland Pacific Northwest, the adoption of no-till (NT) from conventional tillage practices has reduced soil erosion but contributed to stratified soil acidification from the subsurface banding of ammonia-based fertilizers and lack of tillage-based soil mixing. Aluminum (Al) toxicity is a concern in the region as the bioavailability of Al increases with at low soil pH. Lime amendments, which increase soil pH, are one avenue in combatting soil acidification and subsequent Al toxicity. While past research has focused namely on application aspects such as rates, specific properties, and combined effects of liming materials on soil properties, the effects on Al availability and soil microbial communities is largely unexplored in this region. The goal of this study was to characterize the short term (18 mos) effects of two surface-applied lime materials on the vertical distribution of soil chemical properties (i.e. pH, nutrients, metals) and microbial communities of two fields under NT management. Soil samples were collected at 2 cm increments to a 10 cm depth at 6 mos and 18 mos after treatment of the field with either liquid-emulsion or particulate lime products. Both amendments increased soil pH and decreased extractable Al to a depth of 6 cm by 18 mos post-treatment. The bacterial community structures stratified by depth in both soils at the 18 mos sampling point regardless of lime type or whether the soil was treated. The stratification of the communities related to both changes in soil pH and concentrations of extractable Al. In contrast, the fungal communities showed a less pronounced stratification by depth and the communities of only one of the two soils were influenced by soil pH and Al concentrations. The results indicate that the microbial communities are influenced by soil depth, pH and Al availability, although the response may be site dependent.
Technical Abstract: Adoption of no-till (NT) technology in the dryland cropping region of the inland Pacific Northwest (iPNW) has dramatically reduced soil erosion compared to conventional tillage. Soils under continuous NT, however, often produce stratified soil acidification compared with conventional tillage due to subsurface banding of ammonia-based fertilizers and lack of mixing through tillage. Because aluminum (Al) becomes more bioavailable with lower soil pH, Al toxicity is an emerging problem in many crops throughout the region. While past research has focused on levels of various liming materials, the combined effects of liming amendments, soil pH changes, and available Al on microbial communities have not been explored in the soils of this region. Additionally, no work to date has examined a highly resolved depth increment (2cm) to explore these relationships through discrete vertical distribution. The objectives of this study were to: (1) characterize chemical and microbial stratification in continuous NT soils over a highly resolved depth increment; and (2) determine the short-term effects of surface-broadcast lime amendments on chemical stratification and microbial communities. At 18 months post amendment, surface application of lime increased soil pH and decreased extractable Al3+ to a depth of 6 cm. The soil microbial community responded to the soil pH and Al gradient with depth at both sites and both sampling times in which the effects were more pronounced in bacterial community. The 2-cm sampling increments proved important for capturing soil chemical stratification and related shifts in microbial community structure.