EFFECTS OF NITROGEN SOURCE, METHOD OF PLACEMENT AND SOIL TYPE ON SEEDLING EMERGENCE AND BARLEY CROP YIELDS

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Abstract
An inverse correlation between seedling damage caused by urea drilled with the seed and soil cation exchange capacity was determined in eight field trials conducted on soils with a wide range in cation exchange capacity and pH. Seedling damage increased with increasing rates of urea nitrogen and seriously affected potential grain yields of Conquest barley (Hordeum vulgare L.). Drilled NH4NO3 caused greater grain yield increases than drilled urea in a manner inversely related to the seedling damage caused by urea. Drilled NH4NO3 caused greater yield increases than broadcast and incorporated NH4NO3 at 22.4 and 44.8 kg/ha over the 2-yr period. The NH4NO3 broadcast and incorporated in the soil caused greater yield increases than urea similarly applied. The magnitude of the difference was related to soil cation exchange capacity and pH which jointly influenced the quantity of NH3 volatilized.