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Title: DYNAMICS OF EXCHANGEABLE AND NON-EXCHANGEABLE NH4 AND K UNDER LONG-TERM FERTILITY MANAGEMENT

Author
item LIU, YUANJUN - IOWA STATE UNIVERSITY
item Laird, David
item BARAK, PHILLIP - UNIVERSITY OF WISCONSIN

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Nitrogen is an important plant nutrient that often must be supplied as fertilizer to growing crops. Unfortunately, crops only use about one-third of the nitrogen that is applied as fertilizer, and the nitrogen that is not used often ends up as pollution in lakes, streams, and even ground water. To help solve this problem, we are trying to find a way to help plants use fertilizer nitrogen more efficiently. One way to do so is to increase the length of time nitrogen is stored in a soil. By increasing the storage time crops will have more opportunity to use the nitrogen. We have found that there is little possibility for increasing long-term storage of nitrogen in soil minerals by manipulating nitrogen and potassium fertilization rates. However, high rates of potassium fertilization for many years will decrease short-term storage of nitrogen by soil minerals.

Technical Abstract: The objective of this study was to investigate the affect of long-term fertility management on the dynamics of exchangeable and nonexchangeable NH4 and K in soils. To do so, soil samples from 128 long-term (30 years) fertility plots were analyzed for exchangeable NH4 and K and nonexchangeable NH4 and K. Some of the samples were analyzed for K and NH4 fixation capacities. In general levels of exchangeable NH4, nonexchangeable NH4, and nonexchangeable K were similar for all of the long-term fertility treatments. On the other hand, significantly higher levels of exchangeable K were found in plots receiving high rates of K fertilization. Fixation capacities for both NH4 and K were significantly reduced by sustained high rates of K fertilization but were not influenced by rates of N fertilization.