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Kentucky Bluegrass Recovery of Urea‐Derived Nitrogen‐15 Amended with Urease Inhibitor
Author(s) -
Joo Y. K.,
Christians N. E.,
Blackmer A. M.
Publication year - 1991
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1991.03615995005500020039x
Subject(s) - urea , urease , chemistry , poa pratensis , ammonia volatilization from urea , zoology , fertilizer , nitrogen , loam , agronomy , soil water , biochemistry , poaceae , biology , ecology , organic chemistry
Urea is a commonly used N fertilizer on turfgrass areas. Urease inhibitors represent a possible method of reducing volatile loss of NH 3 from treated turf. In this study, the recovery of urea‐N by a Kentucky bluegrass ( Poa pratensis L.) turf was determined in the field by using a 15 N tracer. The urease inhibitor N ‐( n ‐butyl) thiophosphoric triamide (NBPT) also was evaluated as a fertilizer amendment to increase urea‐N efficiency. The study was conducted on a Nicollet (fine‐loamy, mixed, mesic Aquic Hapludoll) soil. Treatments included urea labeled with 5% 15 N applied at the rate of 49 kg ha −1 with NBPT at 0 (urea alone), 0.25, and 0.5% of the weight of N. Grass clippings were collected weekly for 5 wk. Shoots, thatch, and rootzone samples were collected at termination. Total urea‐derived N recovered from 5 wk of clippings ranged from 7.5% from the areas treated with urea alone to 8.1% in the urea + 0.5% NBPT treated areas. The 0.25% NBPT treatment increased N recovery in the 0 to 7.5 cm depth of soil from 13.6 (urea without NBPT) to 22.4%. This NBPT rate also increased N recovery from the whole soil‐plant system from 28.8 (urea without NBPT) to 45.0%, whereas the 0.5% NBPT rate either had no effect or numerically decreased N recovery. The increased N recovery at the low rate of NBPT was probably due to a reduction in NH 3 volatilization. The reducing effect of the higher NBPT treatment may have been due to delayed urea hydrolysis and to subsequent increased free‐urea loss below the rooting zone after an unusual 130 mm rain during the fifth and sixth days after treatment.