Wednesday, November 7, 2007 - 11:45 AM
318-9
The Effects of Moisture Content, Air-Drying, and Extracting Solution on Surface Soil and Subsoil Exchangeable Potassium Levels.
Characteristics such as a soil’s landscape position, moisture content, texture and mineralogy can influence the amount and location of potassium (K) in a profile, and can appreciably influence the variability of soil test K (STK) levels. Plant-available non-exchangeable K (PANK) can be a significant source of K in soils. Commonly used soil tests such as 1 M NH4OAc and Mehlich 3 that do not access this K pool may affect the accuracy of K fertilizer recommendations. An incubation study was performed on the Ap and Bt horizons of soils representing two drainage sequences common to Indiana . The Nappannee-Hoytville sequence consists of lacustrine soils having illitic mineralogies. The Cincinnati-Avonburg-Cobbsfork sequence represents loess derived soils with mixed mineralogies. Soils were incubated at 25°C under two moisture contents (saturation and field capacity) and K was extracted with 1M NH4OAc, Mehlich 3, and NaBPh4 after periods of 1, 4, 7, 10, and 14 days. Each soil was then allowed to air-dry before again being analyzed for K with the extracting solutions. Significant differences (P ≤ 0.05) in extractable K levels were found within incubated moist soils, and between incubated moist soils and their respective air-dry counterparts. Results of the research will be presented and address these differences as well as the following concerns: 1) how clay mineralogy influences the fixation or release of K in soils under different moisture contents, 2) the significance of subsoil K differences and 3) the effect of extracting solution on observed K levels in these soils.
Recorded presentation