Full TGIF Record # 39604
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Publication Type:
Author(s):Watson, Catherine J.; Miller, Helen
Author Affiliation:Agricultural and Environmental Science Division, Department of Agriculture for Northern Ireland, Newforge Lane, Belfast, Northern Ireland BT9 5PX; Faculty of Agriculture and Food Science, The Queen's University of Belfast, Belfast, Northern Ireland
Title:Short-term effects of urea amended with the urease inhibitor N-(n-butyl) thiophosphoric triamide on perennial ryegrass
Source:Plant and Soil. Vol. 184, No. 1, 1996, p. 33-45.
# of Pages:13
Publishing Information:Dordrecht, Netherlands: Kluwer Academic Publishers
Related Web URL:http://link.springer.com/article/10.1007/BF00029272
    Last checked: 10/14/2015
    Notes: Abstract only
Keywords:TIC Keywords: Lolium perenne; Nitrogen recovery; Nitrogen uptake; Metabolism; Urease; Necrosis; Scorch
Abstract/Contents:"The current study investigated the short-term physiological implications of plant nitrogen uptake of urea amended with the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) under both greenhouse and field conditions. ¹5N labelled urea amended with 0.0, 0.01, 0.1 and 0.5% nBTPT (w/w) was surface applied at a rate equivalent to 100 kg N ha⁻1 to perennial ryegrass in a greenhouse pot experiment. Root, shoot and soil fractions were destructively harvested 0.75, 1.75, 4, 7 and 10 days after fertilizer application. Urease activity was determined in each fraction together with ¹5N recovery and a range of chemical analyses. The effect of nBTPT amended urea on leaf tip scorch was evaluated together with the effect of the inhibitor applied on its own on plant urease activity. nBTPT-amended urea dramatically reduced shoot urease activity for the first few days after application compared to unamended urea. The higher the nBTPT concentration the longer the time required for shoot activity to return to that in the unamended treatment. At the highest inhibitor concentration of 0.5% shoot urease activity had returned to that of unamended urea by 10 days. Root urease activity was unaffected by nBTPT in the presence of urea but was affected by nBTPT in the absence of urea. Transient leaf tip scorch was observed approximately 7-15 days after nBTPT + urea application and was greatest with high concentrations of nBTPT and high urea-N application rates. New developing leaves showed no visual sign of tip necrosis. Urea hydrolysis of unamended urea was rapid with only 1.3% urea-N remaining in the soil after 1.75 days. N uptake and metabolism by ryegrass was rapid with ¹5N recovery from unamended urea, in the plant (shoot + root) being 33% after 1.75 days. Most of the ¹5N in the soil following the urea+0.5% nBTPT application was still as urea after 1.75 days, yet ¹5N plant recovery at this time was 25% (root + shoot). This together with other evidence, suggests that if urea hydrolysis in soil is delayed by nBTPT then urea can be taken up by ryegrass as the intact molecule, albeit at a significantly slower initial rate of uptake than NH⁺₄ -N. Protein and water soluble carbohydrate content of the plant were not significantly affected by amending urea with nBTPT however, there was a significant effect on the composition of amino acids in the roots and shoots, suggesting a difference in metabolism. Although nBTPT-amended urea affected plant urease activity and caused some leaf-tip scorch the effects were transient and short-lived. The previously reported benefit of nBTPT in reducing NH₃ volatilization of urea would appear to far outweigh any of the observed short-term effects, as dry-matter production of ryegrass is increased."
ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Watson, C. J., and H. Miller. 1996. Short-term effects of urea amended with the urease inhibitor N-(n-butyl) thiophosphoric triamide on perennial ryegrass. Plant Soil. 184(1):p. 33-45.
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