Sulfur-coated Urea as a Slow-release Nitrogen Source for Onions

Field studies with onions ( Allium cepa L. cv Monarch) were conducted in 1980 and 1981 to compare preplant-banded sulfur-coated urea (SCU) with preplant-banded and split applications of urea. Treatments were evaluated at two N rates, 56 and 224 kg·ha −1 . Root NO 3 -N and soil NO 3 -N concentrations in bed centers indicated slower release of N from SCU than from urea. Nevertheless, total and large bulb (> 76 mm in diameter) yields and N uptake in onion bulbs and leaves from SCU were significantly higher under low-N conditions than with preplant urea, but did not differ significantly from split urea treatments.