Response of Yield and Quality of Garlic to Nitrogen Sources and Foliar Spray with Sulfur Treatments

Abstract

to study the effect of nitrogen forms (ammonium nitrate and urea) and sulfur treatments (0, 5, 10 and 15 mM) from two sources (potassium sulphate and calcium sulphate) on garlic yield, chlorophyll, carbohydrates, phenols, nitrate and elements content. Results revealed that ammonium nitrate-fertilized plants had the highest nitrate content in the absence of sulfur treatments. However, plant growth, yield, chlorophyll, phenols, NPK, Ca and S reached the maximum values and nitrate content decreased when plants were sprayed with potassium sulphate at 10 mM. Potassium sulphate was more favorable than calcium sulphate for improving the plant growth, yield and other bulb quality such as phenols and S content. Urea-fertilized plants showed less bulb yield and nitrate content than ammonium nitrate-fertilized plants, but higher than un-fertilized plants. Chlorophyll, nitrogen, phenols and S content were lower and the carbohydrates content was higher in plants grown with un-fertilized than in well fertilized with nitrogen. The results showed that N and S nutrition during the growth and bulb production are strongly coupled. Their interactions are synergistic at suitable form of nitrogen (ammonium nitrate) as well as at optimum rate of potassium sulphate (10 mM). However, excessive level of potassium sulphate (15 mM) seems to be antagonistic. Together, the results indicate that S spraying is required to improve N-use efficiency and thus increasing the bulb yield with high minerals nutrient such S and N content which are very important for S-containing bioactive compounds in garlic.