Essential Hemp Oil / 2. Material and Methods

2. Material and Methods

To asses the influence of harvest time, seed density and pollination, field and greenhouse experiments were carried out.

Field experiments
Plots were sown on the 17th of april 1997 in Tenniken (Switzerland) near Basel (604 m.o.s.; 7°50' E, 47°30' N) on brown soil, fertilized with 120 kg/ha N.

Harvest time experiment
Four strains (Tab. 1) sown at a density of 30 kg/ha were harvested several dates between the the 4th of august and the 14th of october. The developmental stage of the plants was determined at every harvest. In biological terms the harvest was done between the beginning of female flowering and the senescence of the plants. The upper 50 cm of the plants inflorescences and leaves had been used to distil essential oil as described below. Plant material was either used fresh or had been kept frozen at -20°C until distillation.

Seed density experiment
Three strains (Tab. 1) were sown in randomized plots with four replications. The germination capacity of all strains was 80%. Sowing rates of 2 and 5 kg/ha (row width was 36 cm) and of 10, 30 and 60 kg/ha (row width was 18 cm) were tested. Weed controll was only necessary at 2 and 5 kg/ha. It was carried out by hand. Harvest took place depending on the strain at seed maturity, that means when about 75% of the seeds of the whole poulation was matured. After drying the buds were separated from the stalks by hand.

Table 1 Used strains and their provenance

Greenhouse experiment
The strain Kompolti was grown in pots in two identical glasshouse chambres between the 4th of august and the 20th of november 1997. Plants were fertilized with Wuxal®. Thrips, present at the very beginning of the experiment, were controlled with Cymbush®.
About four weeks after sowing the light was reduced from 18 to 12 hours to initiate flowering. Male plants were removed in both chambres to avoid uncontrolled pollinating. Three weeks after the daylength change in one chamber pollination was accomplished by daily shaking mature male plants. Two month later, when seeds had been totaly matured (75-100%), plants were harvested.

Distillation of the essential oil
Distillation took place in a copper pot with 1 l tab water. The amount of plant material was 350-450g freshweight, containig mainly inflorescences, some leaves but never stalks. Plant material was separated by hand and came from the upper 50 cm of the plant. Condensation was done by simple water cooling. Essential oil was collected using a separating funnel.

Analysis of the oils
Chemical analysis were performed with GC (on a Supelcowax 10 column) and GC/MS in the Central laboratory in CH-2052 Biel.
The quality of an essential oil can not be estimated in metric terms. Essential oil is composed of hundreds of substances from which only a small part are identified yet. It is not known which compound or mixture of compounds is responsible for a good or a bad scent. It just can be evaluated whether it smells good or not, respectively better or worse than another ones.
Scent tests were done by two essential oils specialists (A. and L. Mächler, Essencia AG, CH-8400 Winterthur). The oils of the harvest time experiment were compared within strains to get a ordinal ranking list for each strain depending on the harvest time. Greenhouse experiment derived oils were compared in pairs of one oil sample from pollinated and one sample of non pollinated plants.

Titel

Abstract

Contact