EFFECTS OF PLACEMENT OF UREA WITH A UREASE INHIBITOR ON SEEDLING EMERGENCE, N-UPTAKE AND DRY-MATTER YIELD OF WHEAT

Growth chamber studies were conducted to determine the effect of seed-placed and surface dribble-banded urea fertilizer, with and without the addition of two levels of the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) on seedling emergence, vegetative yield and nitrogen accumulation of hard red spring wheat. Seedling emergence was reduced with increasing applications of seed-placed urea, but nBTPT reduced the damage from seed-placed urea. The 0.15% inhibitor level was as effective as the 0.25% level in reducing seedling damage. Vegetative yield increased with application of urea fertilizer but no difference in vegetative yield resulted from varying fertilizer placement or additions of nBTPT. Nitrogen accumulation increased with increasing N application and with the use of the urease inhibitor, indicating an increase in N availability due to slowing of urea hydrolysis. Use of the urease inhibitor nBTPT shows promise in reducing seedling damage from seed-placed urea fertilizer and increasing the utilization of seed-placed and surface-applied urea fertilizer on a black Chernozemic soil. Further studies are in progress to assess the performance of nBTPT under field conditions.