Agronomic assessment and15N recovery of urea amended with the urease inhibitor nBTPT (N-(n-butyl) thiophosphoric triamide) for temperate grassland

✍ Scribed by Catherine J. Watson; P. Poland; H. Miller; M. B. D. Allen; M. K. Garrett; C. B. Christianson

• Publisher: Springer
• Year: 1994
• Tongue: English
• Weight: 711 KB
• Volume: 161
• Category: Article
• ISSN: 0032-079X
• DOI: 10.1007/bf00046388

✦ Synopsis

Three field experiments were undertaken concurrently at one site to evaluate a range of surface-applied nBTPT-amended urea products (0.01, 0.05, 0.1, 0.25 and 0.5% nBTPT w/w) on NH3 volatilization, grass yield and 15N recovery in the plant-soil system. Each experiment was repeated on five separate occasions over the 1992 growing season to cover a range of weather conditions. Total NH3 loss from unamended-urea ranged from 5.5% in early May to 20.8% in June. The inhibitor was highly effective in reducing ammonia volatilization and delaying the time at which maximum rate of NH3 loss occurred. Over all time periods the % inhibition was 50.4, 82.8, 89.0, 96.5 and 97.0% at the 0.01, 0.05, 0.1, 0.25 and 0.5% nBTPT levels respectively. There was no significant difference in the overall % inhibition in ammonia loss at different times suggesting that the effectiveness of the inhibitor was not dependent on climatic conditions. Over all times incorporation of nBTPT at the 0.05% level increased dry-matter yield by 9% compared to urea alone and increased the shoot recovery of N from 66.7% to 80.9%. Nitrogen saved from volatilization was taken up by the plant, however, the subsequent translation into dry-matter yield appeared to be adversely affected at the high inhibitor rates.

There was no significant effect of inhibitor on 15N recovery in soil at any depth down to 15 cms. nBTPT significantly increased (p < 0.001) the % N derived from fertilizer (% N dff) in the shoot compared to unamended-urea and increased (p < 0.01) the shoot recovery of tSN from 32% up to 39%. Total 15N recovery in the soil-plant system was increased by up to 17% by amending urea with nBTPT. This urease inhibitor has been shown to improve the efficiency of urea however, its potential for the European market will be dependent on economic factors.