Ecophysiological aspects of nitrogen management in drip irrigated onion (Allium cepa L.).

Environmental factors that promote bolting in long-day onions (cv Valencian a de Grano) were examined. Plants were grown at various densities and light levels and it was found that the upper temperature limit for flower induct ion was approximately 17 degrees C and that low irradiance impairs flower p roduction. To control of bolting whilst maintaining yield requires high lev els of soil N availability during growth and a leaf area index less than 3. 5.