OPTIMIZATION OF HARVESTING TIME AND ROW SPACING FOR THE QUALITY OIL IN JAPANESE MINT (MENTHA ARVENSIS L.) VARIETIES

In order to optimize row spacing and harvesting schedule for Japanese mint, three varieties (MAS-1, HY-77 and PBS-1) were planted at three row spacings (45, 60 and 75 cm) and harvested at three times (120, 135 and 150 days after planting) at the Research Farm of the Department of Agronomy, Punjab Agricultural University, Ludhiana during the summer seasons of 1991 and 1992. The experiment was laid out in split plot design keeping combination of varieties and row spacing in the main plots and harvesting time in the sub-plots, on a loamy sand soil with four replications.

The results indicated that variety PBS-1 out yielded MAS-1 and HY-77 in oil yield. The performance of varieties differed under various row spacings. PBS-1 and MAS-1 recorded highest oil yield when planted at 45–60 cm apart whereas, HY-77 produced equal yield at all the three, row spacings. The time of harvesting depends upon the temperature conditions prevailed after planting. To get highest oil yield the crop may be harvested 120–135 (lays after planting or when the crop has enjoyed about 2680 heat units. The content of menthol and menthyl acetate increased but menthone content decreased with delay in harvesting from 120 to 150 days after planting.