THE EFFECT OF PLANT DENSITY ON THE PRODUCTION OF VALERIAN ROOT

Two valerian (Valeriana officinalis L.) trials were conducted to examine the relationship between plant population and dried root yield. Six plant densities from 6 to 33 plants/m² planted with a constant row width of 30cm, were compared. The valerian was grown and harvested in one season in the first trial and grown for two seasons before harvest in the second trial. The root production/plant declined as the plant population rose at each site. The reduction of root weight was most rapid with increasing plant numbers at the low populations. The root yield/plant at the highest population in the single season crop was 30% of the lowest population (84g) and in the two season crop, 16% of the lowest population (105g). On an area basis, the root yield in the annual crop rose with each increase in plant population to a maximum of 8t/ha dried root. In the trial conducted over two seasons, plant population had no effect on the yield/unit area. These results show that there are considerable yield advantages obtained by planting valerian at plant populations above the current recommendations of 6–10 plants/m² for annual crops but not for biennial crops.