ISSN:
1573-5036
Keywords:
actual N loss
;
flooded soils
;
15N balance
;
potential N loss
;
urea
;
water-soluble N
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract One day after application, urea-N remaining in the floodwater and determined as water-soluble N (urea-N + NH4 +-N) was used to calculate the potential N loss from lowland rice soils. Actual N loss calculated from 15N balance measurements using forced air exchange (airflow rate: 20 L min-1) in greenhouse pots. Conditions for variable potential N loss were created by manipulating the method of urea application and duration of presubmergence or by selecting soils with diverse cation exchange capacities (CEC). Potential N loss tended to be lower than actual N loss; the differences were, however, nonsignificant. The method of urea application that led to the lowest potential N loss from a Guthrie silty clay loam (Typic Fragiaquult) also led to the least 15N loss and vice-versa (r=0.99**). Duration of presubmergence did not alter the relationship between potential and actual N loss although it influenced the rate of urea hydrolysis in floodwater. The primary depencence of actual N loss on water-soluble N was maintained in soils differing in CEC (r=0.83**). The association between potential and actual N loss was closer for high-CEC soils (≥ 20 cmol [+] kg-1 soil, r=0.91**) than for low-CEC soils (〈20 cmol [+] kg-1 soil, r=0.85**). Ammonia volatilization could be more closely predicted by potential N loss than could apparent denitrification. The results of this study suggest that potential N loss calculated from one-time determination of water-soluble N in floodwater can be a good index of actual N loss from flooded, puddled rice soils. Notable exceptions are to be expected for soils in which water-soluble N gets lost from floodwater either before (soils with fast urea hydrolysis in floodwater) or after (soils with steady leaching) determination of potential N loss.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00013093
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