Observations and Experiments on the Multiplication, Cultivation, and Management of Vetiver Grass Conducted in China in the l950's
Xia Hanping (South China Institute of Botany, The Chinese Academy of Sciences, Guangzhou, China)
Abstract This paper systematically summarizes observations and experiments on methods to rapidly multiply vetiver conducted in China in the 1950's. Besides the general practice of propagation by division of roots, other successful propagation methods developed from experiments included: 1) multiplication by stem-culm cuttings, 2) multiplication by pedicel-culm cuttings, 3) multiplication by longitudinal-slit stems, and 4) multiplication through pruning tops. New cultivation techniques were developed that promoted rapid field establishment included: 1) water-cultivation for accelerating roots, 2) heeling-in for improved root establishment , 3) dipping roots, 4) retaining mother tillers left in soil, and 5) oblique planting. Management measures that enhanced tillering rates had: 1) intensive cultivation and strengthening management, 2) proper pruning, 3) and rational close planting. Obviously, these successful multiplication, cultivation, and management methods can play an instructive and reference role for the similar work in the future.
Vetiver grass (Vetiveria zizanioides) was introduced to China in the middle 1950's. At that time, some multiplication, cultivation and management experiments on this plant were conducted in China. The purpose for introducing vetiver was for the production of Essential Oil from vetiver roots. Seedlings for propagation were scarce; so experiments were undertaken concentrating on two aspects: first, on the rapid multiplication of seedlings , and secondly on breeding roots that yielded oil of high quality and content. This paper summarizes the research and the results
1 INTRODUCTION OF VETIVER
The first introductory paper Oil vetiver was published in the magazine of Tropical Crops (in Chinese) in 1957, whose title was just "Vetiveria zizanioides". This paper covered in detail five different aspects of vetiver: 1) production; 2) the plant; 3) multiplication and cultivation; 4) harvest and processing; and 5) characteristic of vetiver oil. There are several points worth mentioning in this article. They are: China's vetiver was introduced from Indonesia in 1956. (It has been widely believed that China's vetiver was from India).
The undomesticated vetiver had been found in Hainan Island of China. (As a matter of fact, there was a much larger area, approximately 6,000-7,000 ha, of wild vetiver communities, maybe Vetiveria nigritana, found in Guangdong by South China Institute of Botany in 1957.)
Vetiver roots are 3-4 mm in diameter, and 1-1.5 m deep. It can produce dry roots 100-150 kg per mu (one-fifteenth hectare) 1 year after planting, from which can be refined 2-3 kg vetiver oil.
Vetiver grass is rarely seeds, and is mainly replicated by vegetative propagation. Prior to planting their tops should be pruned to about 20 cm, and the number of tillers per slip should be 2-3.
The plant generally performs better in free and well drained soils, and best in young soils developed from volcanic ash. The oil content will decrease if it is planted in clayed soils. The grass grows best under full sunshine, and is not a shade-tolerant. The oil content of roots is generally some 2-2.5%. 18-month-old roots contain the most oil with the best fragrance. The older the root the greater the density of oil.
In addition, there was another introductory paper on vetiver oil. This paper, entitled "Vetiver Oil", introduced the production and processing of vetiver oil in some major oil producing countries and regions including Java, Reunion, Haiti, India, and some countries from South America. It also made reference to chemical ingredients, physical and chemical characteristics, functions and uses of vetiver.
2 SOME SUCCESSFUL METHODS FOR PROPAGATING VETIVER
Since vetiver has difficulty in producing viable seeds, the general propagation approach is through division of roots. The availability of vetiver seedlings was very deficient in the late 1950s, so priority was given to experimenting on the multiplication of materials. The successful propagation methods obtained from these experiments and surveys are as follows.
2.1 Multiplication by Stem-culm Cuttings
No matter how many nodes, mono-, bi-, or poly-node, are contained in a culm, old culms from the first four nodes in the base part of a stem have the highest survival rate, which goes up to about. 50-60%; whereas the culms from the 5-6th nodes only have 20-30% survival rate. The further the culms are from the base part, the lower their survival rates eventually to zero. In the same nodes, those which are deprived of sheaths and have revealed "bud-eyes" and "root points" sprout more rapidly, and produce more roots, than those which are not deprived of their sheaths. This is because the bud ~eyes~ and root points in culms whose sheaths are peeled off are capable of contacting directly with moisture in soil, which promotes root points to stretch and bud-eyes to sprout. If older cuttings are put in sand with saturated water, they will show "white dots" next day, and produce new roots in the third day; if younger cuttings are used it will takes more than 20 days, but they do not become dry or dead.
2.2 Multiplication by Pedicel-culm Cuttings
During the period of flowering, pull open leaves lying next to the 5 - 8th nodes, and cut off the pedicel from the top 3-4 nodes. Over 5-6 days after the top is cut, prune the pedicel culm at 1-2 cm from the ground. Divide each node of the pedicel into one section, then dip the sections into 0.01 % KMnO4 solution for 5 -10 minutes. After that plant them in a nursery. The nursery should well drained and fertile, water sufficient, and be in the shade. Irrigation is given 2-4 times per day, new roots will grow out some 10 days after planting.
2.3 Multiplication by Longitudinal-slit Stems
This method is interesting. Vetiver stems have opposite axillary buds and radicles. If a strong stem is longitudinally slit into two halves, then both can produce new tillers and roots. Longitudinal-slit seedlings should be cultivated in shade and the management must be meticulous. It is necessary to usually irrigate the bed in order to keep it wet. New roots will appear after stems have been transplanted for 6 days, and their establishment rate may be up to 100%. Furthermore, the propagation with longitudinal-slit stems has a pretty rapid tiller-formation; and can enhance multiplication speed by 2-5 times as compared to non-longitudinal-slit approach.
2.4 Multiplication through Pruning Tops
This is a quite novel approach. The main operation is as follows. Cut the top from the growth point when the plant grows up to 5-6 nodes; the purpose is to control top growth. Then peel off sheaths node by node to accelerate axillary buds aging. After top pruning and sheath removing, nutrients in plant will concentrate chiefly on the buds, thus new seedlings are beginning to sprout from the buds in 1-2 weeks. When the seedlings grow up to round 20 cm, pick them up with the mother buds and culms together. Then heel in them under shade to produce roots as soon as possible. After new roots come out in about one week, they can be outplanted. This propagation way usually has a establishment rate of over 95%, and its speed of forming seedlings is far faster than propagation by pedicel-culm cuttings.
3 CULTIVATION TECHNIQUES FOR PROMOTION ESTABLISHMENT
3.1 Water-cultivation for Accelerating Root Growth
The method of water cultivation for speeding root growth is quite simple and is accomplished by laying the cuttings or root divisions vertically in 5-centimeter-deep water (e.g. shallow pool) for 7-10 days.
This advantages of this method are as follows:
_ Has quicker growth and tillering Through water cultivation, seedlings no longer undergo the green-turning process, but grow directly. Thus they can produce tillers in advance.
_ Roots rapidly. Water cultivation makes seedlings strike new roots only in 2-3 days, whereas the ordinary transplanting way takes at least one week. (In spring 1997, we did the same experiment, the result was that fastest new roots were produced in 3 days, and the slowest in a week or so.)
_ Increased the survival rates, and better promotion of growth and development. While cuttings are used as multiplication materials, they will not take roots and from tillers until transplanting after 10 days or a longer, respectively, even if cuttings are from the older culms. If cuttings are the younger culms, the majority do not survive after transplanting. Through water cultivation, however, old stems grow new roots and leaves only in 2-3 days; young stems also take roots only in 10-15 days, and only a few become dry and dead.
3.2 Heel-in for Taking Roots
An ad hoc survey showed that the survival rate of vetiver through heel-in was 97.5%, whereas that with no heel-in was only 92.3%. Another experiment indicated no difference in survival rates in the rainy season between vetiver transplanted on the same day of uprooting and vetiver transplanted through heel-in. Therefore, it is best, in the rainy season, to plant vetiver immediately after it is dug up. In the dry season, however, heel-in for striking roots is an ideal measure to guarantee a high survival rate (Table 1). Heel-in can enhance the survival rate, but the time of heel-in is important, and it is best at 6-10 days after transplanting when new roots reach 2-4 cm.
Table 1 Comparison of effects of heel-in and non heel-in on the survival rate of vetiver
Weather condition Treatment Survival rate(%) Note
High temperature Heel-in 98.0 1
Drought Non heel-in 76.8 2
Low temperature Heel-in 92.0 3
Drought Non heel-in 81.0 4
1 ) Both treatments are 500 clumps and
2) Planting oil July 6, checking Aug. 4
3 ) Both treatments are 200 clumps
4) Planting on Jan. 17, checking Feb.10
3.3 Dipping Roots
Before planting, dip vetiver roots in 5-25 ppm 2,4-D, dilute fecal sewage, or even slurry. This method may increase survival rates, and promote tiller formation and growth. For example, the numbers of tillers and new roots whose seedlings were dipped into dilute ox-feces and water increased by 26.4% and 80.2%, respectively, compared with those seedlings not during the first three months after transplanting.
3.4 Keeping Mother Tillers in the Soil
When lifting from a nursery, keep 2-3 tillers from per clump in the ground to gain a more rapid multiplication rate for the next nursery. A special trial compares the tillering rate of the following 2 treatments : 1) the plants from mother plants left in soil, and 2) the plants replanted with the same mother plants. Both start with 10 tillers. After 35 days , treatment 1 goes up to 53 tillers , and treatment 2 becomes only 6 tillers. It is clear that till ring rate with mother plants left in the soil is by far the quickest.
3.5 Oblique Planting
Plant vetiver obliquely into soil when transplanting. It is possibly better to plant at an angle of about 45-600 rather than vertically.
4 MANAGEMENT MEASURES FOR ENHANCING TILLERING RATE
4.1 Intensive Cultivation and Improved Management
The nursery must have fertile soil, adequate moisture and sufficient sunshine. When clumps of vetiver are divided into pieces for seedlings, it would be best to tear them where they tare best, otherwise seedlings will be damaged. Basal manure and water should be applied when seedlings are planted. Number of tillers may be enhanced by 2-3 times if good, enough basal manure is applied. Top dressing, liquid fertilizer is best, should be applied twice a month. Vetiver is drought-resistant, but the nursery should be supplied with sufficient water; so irrigation should be given once per 2-3 days if there is no rain. There is a trial that indicates the survival rate of vetiver planted in a wet field is 59.8%, and tillers number per clump averages 13.4, but in a dry field both are only 57.5% and 2.7, respectively, in the same period.
4.2 Proper Pruning
After transplanting seedlings to a nursery for 10 months (August -June), the nursery was set up for 4 treatments: 1 ) unpruned and unfertilized, 2) pruned and unfertilized, 3) unpruned and fertilized, and 4) pruned and fertilized. The plants were cut to 30 cm, fertilization with night soil, and observation time was 1 month. The results were that treatment 2 enhanced the number of tillers by 46.4%, but treatment 1 only by 17.7%; treatment 4 increases the number of tillers by
52.6%, whereas treatment 3 only by 26.9%. However, if the plants are pruned in less than 4 months after transplanting (February -June), they will suffer physical damages owing to their young age, which retards the growth and tillering. In the experiment above, the tillers number for treatment 2 increased only by 8.2%, but treatment 1 by 41.4%, after transplanting for less than 4 months.
The reasons why pruning can promote growing and tillering are because: 1) Vetiver is 150-160 cm high, and the bed's coverage usually exceeds 90% when the plants are up to this height, thereby results in closing between rows. Vetiver, the C4 plant, demands lots of sunshine for its growth and development, however. Therefore, proper pruning may lessen the closing density and heighten sunshine density in all parts of the plant, especially improved photosynthesis of the new tillers . 2) prunings comprise mainly old stems and leaves. There is no serious effect of pruning them on the plant; on the contrary, removal of old parts can diminish the consumption of moisture and nutrients. 3) Pruning also cuts off pedicels or inhibits the plants from moving into the stage of reproductive growth, which would consume a great ideal of water and nutrients owing to flowering and seeding. 4) That old parts when cut off possibly produces stimulation to the plant itself, thus can also improve its growth and tillering.
4.3 Rational Close Planting
Vetiver has a very strong ability to produce new tillers, and therefore planting density has a significant influence on growth and tillering. An ad hoc trial indicates that different planting densities, according to table 2, 1 tiller per clump, produce the tangibly different numbers of tillers in 2 months. Certainly, it does not mean from table 2 that the sparser the planting density is, the better. Generally speaking, the planting density of 20 cm to 30 cm for multiplication is pretty ideal.
Table 2 Effects of different planting densities on tiller formation
|Spacing||Net Increment of Tillers per Clump|
|15 x 20 cm||3.8|
|20 x 20 cm||4.4|
|20 x 25 cm||5.6|
|20 x 30 cm||6.6|
|30 x 35 cm||7.0|
5 OTHER ASPECTS NEEDING CONSIDERATION
5.1 Shallow Planting Is Probably Better Than Deep Planting
Table 3 indicates that vetiver planted 3-4 cm deep is best, 5-6 cm second, and 7-8 cm worst, no matter which aspect, survival rate or tillers number of per clump. It is clear from this survey that shallow planting is better than deep planting. The crown must be buried in the ground, however. In addition, in the dry season the plants can not be inserted too shallowly, otherwise they would suffer from drought and result in a decrease of survival rate.
Table 3 Effects of different planting depths on establishment rate and tillering rate
|Planting Depth (cm)||Estab. Rate (%)||# tillers/clump at 4 months|
5.2 Keeping Long Roots Is Possibly Better Than Keeping Short Roots
An experiment tested 2 treatments: pruning roots to 15 cm, and to 4 cm. After transplanting for 3 months, the result shows that the plants with 15 cm long roots had more than more 8.2% of tiller numbers than those with 4 cm long roots. When heeling in, the former had 19.8% increase in the rate of tiller than the latter, in the same period. The difference, however, gradually dwindles as time goes on. Furthermore, effects of the two treatments had no significant effect on the survival rates. In general, 10 cm long roots are enough; too long roots are not recommended.
5.3 How Many Tillers Per Clump Should Be Planted
Three treatments in an experiment were set up : 1 tiller, 2 tillers, and 3 tillers per clump. After 2 months, their survival rates and new tiller increments were significant (table 4). Obviously, it is better to plant 2-3 tillers per clump in order to get the best establishment rate. It is certainly feasible to plant 1 tiller for each clump when seedlings are scarce. However, a rule, as mentioned above, is to tear off clumps at the place most easily-torn.
Table 4 Effects of different numbers planting on survival and tillering rates Treatment
|# Tillers per Clump||Survival rate (%)||Net increment of tillers per clump||Net increment of tillers per tiller
The author are grateful to Professor He Daoquan for providing some precious reference material.
(19 reference 5 are not used here because they are in Chinese. Any of you who are interested in them please contact the author).