Timed application of ammonium nitrate for optimum yield of uniform sweetpotato (lpomoea batatas) tuberous roots

Abstract

Sweetpotato, Ipomoea batatas L., was grown under 6 different nitrogen treatments for two lengths of time in pots of vermiculite and watered with a nutrient solution. The treatments were 50kg/Ha ammonium nitrate (NH₄NO₃) applied either when the slips (stem cuttings) were planted, or after 6 days, after 12 days, after 18 days or after 24 days. The control did not receive any ammonium nitrate treatment. All treatments received the recommended nutrients other than nitrogen levels from the date of planting. Plants were harvested at 56 days and at 122 days. The results showed that there was a significant difference between treatments with respect to total root fresh weight and tuberous root fresh weight on both harvest occasions. Nitrogen applied at or before 18 days caused the greatest increase in weight, while application of nitrogen between 6 and 12 days most likely coincides with tuber initiation. This makes nitrogen available to all tuberous roots at the same time and therefore all roots can compete equally, resulting in a larger number of uniform roots.