At the Quilamapu Experiment Station (INIA), Chile, three field experiments were carried out during 19861988, to evaluate the efficiency of N use by wheat plants, when this nutrient is applied as Chilean nitrate or as Urea, at differents dates, to spring wheat varieties.
The trials were set up under irrigation, in a split plot designo The treatments (7) were the N application dates, and the subtreatments (2) were the N fertilizers, Chilean nitrate or Urea. Both fertilizers were applied once at arate of 150 kg N/ha, on the soil surface the first day of each month, from May till November. Since planting date was always August first, the N treatments were applied befare, during and after seeding time.
Evaluations were: grain yield and yield components, biomass and N of grain and straw.
The most important conclusions were:
1. Chilean Nitrate and Urea applied at differents dates in spring wheat had the same performance.
2. Dates of N applications affected grain yield and other agronomic characteristics.
3. Early N applications (befare wheat planting) or late (spike emergence) negatively affected the grain production efficiency, N extraction, and N recovery by the wheat plant.
4. Accumulated rainfall between the fertilizers' applications and plant emergency, might explain the variations of wheat N extraction capacity. |
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