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 th e addition of two levels of the urease inhibitor N-(n-butyl) thiophosp horic triamide (nBTPT) on seedling emergence, vegetative yield and nit rogen accumulation of hard red spring wheat. Seedling emergence was re duced with increasing applications of seed-placed urea, but nBTPT redu ced 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 addi tions of nBTPT. Nitrogen accumulation increased with increasing N appl ication and with the use of the urease inhibitor, indicating an increa se in N availability due to slowing of urea hydrolysis. Use of the ure ase inhibitor nBTPT shows promise in reducing seedling damage from see d-placed urea fertilizer and increasing the utilization of seed-placed and surface-applied urea fertilizer on a black Chernozemic soil. Furt her studies are in progress to assess the performance of nBTPT under f ield conditions.