Effects of topping times on growth and yield of three sweet basil (Ocimum basilicum L.) varieties cultivated in the net house

The study was carried out from June to December, 2014. The objective of this study was to determine a suitable topping time for sweet basil variety grown in the net house at Research and Development Center for Hi-Tech Agriculture Ho Chi Minh City. A two-factorial experiment was designed by the CRD (Completely Randomized Design) with three replications. Factor A consisted of three sweet basil varieties (TN12 as Control, TN33, and TN39) and the factor B was the topping times including untopping (the control), the topping when sweet basil at the four-leaves, at the six-leaves and at the eight-leaves period. The results showed that variety TN39 was suitable for extracting basil-oil because of the highest yield (3,365.4 kg/1,000 m2) and high total essential oil content (0.25%). Variety TN12 could be grown for fresh-eating spicy. The variety TN12 resulted in the fairly high yield (1,955.4 kg/1,000 m2) and total essential oil content (0.20%) with good taste. Topping the basil plant at the six-leaves period reached the highest yield of 2,172.3 kg/1,000 m2.