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Scientific abstracts

Potassium Buffering Characteristics of Three Soils Low in Exchangeable Potassium
Wang, Jim J.; Harrell, Dustin L.; Bell, Paul F.
Published in:
Soil Sci. Soc. Am. J. 68:654-661 (2004), English


Plant availability of soil K is controlled by dynamic interactions among its different pools. Misunderstanding of these dynamics leads to mismanagement of soil fertility. This study was conducted to evaluate buffering characteristics of low exchangeable-K soils that showed different sugarcane (Saccharum spp. L.) responses to K amendment. Three silt loams, Crowley (fine, smectitic, hyperthermic Typic Albaqualfs), Dundee (fine-silty, mixed, active, thermic Typic Endoaqualfs), and Norwood (fine-silty, mixed, superactive, hyperthermic Fluventic Eutrudepts), were evaluated by using a modified quantity/intensity (Q/I) approach, which allows partitioning of K changes in the soil-solution system into exchangeable and nonexchangeable pools. Total potential buffering capacity (PBCt) was found to correlate significantly (r = 0.97, P < 0.01) with the buffering capacity due to nonexchangeable K (PBCn) rather with that due to exchangeable K (PBCe). Impact factor ({beta}), a measure of effect of added K on nonexchangeable K, was inversely correlated with a soil's conversion magnitude ({alpha}) of converting added K to exchangeable K (r = 0.95, P < 0.01). Of the three soils, Dundee exhibited much smaller {beta} values than Crowley and Norwood but the soil converted much of added K to exchangeable K (60-65%) throughout its surface and subsurface soils. Both Crowley and Norwood possessed higher PBCt as well as higher PBCn and PBCe than Dundee, but Crowley required relatively lower critical exchangeable K (EKr) and solution K (CKr) levels below which release of nonexchangeable K was initiated. The overall results indicated that the partitioned Q/I approach could be used to explicitly evaluate short-term K dynamics in soil-solution systems. The nonexchangeable K buffering characteristics along with the differences between critical levels (EKr or CKr and EK0 or CK0) have important implications in assessing the likelihood of nonexchangeable K release and could be calibrated for soil fertility management.

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