Submitted to: Soil Ecology Society Conference
Publication Type: Abstract Only
Publication Acceptance Date: 2/24/2003
Publication Date: 5/3/2003
Citation: WUEST, S.B. SOIL NUTRIENT, TEMPERATURE, AND MOISTURE DYNAMICS: COMPARING NO-TILL TO TILLED WITH AND WITHOUT RESIDUE COVER. SOIL ECOLOGY SOCIETY NINTH BIANNUAL INTERNATION CONFERENCE ABSTRACTS. 2003.
Technical Abstract: An experiment planted annually to winter wheat compares no-till versus inversion tillage, with and without incorporation of surface residues. The location is in the inland Pacific Northwest, which has a Mediterranean climate consisting of cool, wet winters and hot, dry summers. The soil is a deep loess deposit of silt loam. Subsurface temperatures were continuously monitored during the fall and winter. Monthly soil samples to 30 cm in 5 cm increments revealed differences in pH, nitrogen, carbon, phosphorus, and moisture. The dynamics of ammonium and nitrate were the most striking. When surface residues were buried using normal inversion tillage, fertilizer ammonium quickly disappeared in the fall and remained below 7 mg kg^-1 for the remainder of the crop year. Under no-till, ammonium remained above 18 mg kg^-1 until spring. The third treatment, where surface residues were removed and then replaced after tillage, gave intermediate levels of ammonium. Nitrate also differed greatly in time and space between the three treatments. Phosphorous and pH differed in narrow zones, as might be expected due to a lack of soil mixing under no-till. The measurements were made during the third year of no-till treatment, and stratification of total organic C and N was apparent. These measurements are ongoing, and my goal is to devise a strategy for discovering the physical and biological factors that result in such large differences in nitrogen dynamics. Possible additional measurements might be aeration and denitrification.