Can Rubber Be Grown in New Zealand?

New Zealand Journal of Agriculture, Volume 65, Issue 6, 15 December 1942, Page 325

Can Rubber Be Grown in New Zealand?

By

R. E. R. GRIMMETT,

Chief Agricultural Chemist, Wellington.

THE remarkable productivity of the rubber tree, .Hevea Brasiliensis, under tropical plantation culture as in the East Indies, tended before the war to discourage interest in rubberproducing plants more suited to temperate climates. Guayule Guayule, a woody perennial shrub belonging to the family compositae had certainly been exploited to some extent in its homeland, Mexico, and had even been cultivated commercially in

Southern California, but it is a plant of dry regions with limited adaptability. It is more likely to be successful in Australia, where experiments in growing it are already under way, than in New Zealand. Under suitable conditions it can yield nearly as much rubber per acre as Hevea. Kok-Saghyz Russian Developments.— only extensive investigations were those made in Russia, in an endeavour to secure self-sufficiency in raw rubber. During 1931-33, expeditions collected plants from many parts of the Soviet Union, and tested them for rubber content and suitability for culture. As a result several species of dandelion (Taraxacum') and Scorzonera were selected for trial, and one of these, Taraxacum Kok-saghyz, a native of the Tian Shan Mountains of Kazakstan, was found adaptable to cultivation on an extensive scale. Information regarding Kok-saghyz and its behaviour as a farm crop has

until recently been very meagre and difficult to obtain, and not until this year have seeds been procurable from Russia. Even now the few authoritative accounts that have been published are somewhat contradictory in regard to important aspects. For example “Soils and Fertilisers” issued by the Imperial Bureau of Soil Science states “The practice of growing special' plantations of Kok-saghyz for seed, and harvesting the roots of the rubber plantations at the end of the first year is rapidly being superseded by maintaining two-year plantations in which the seed is harvested after one, and rubber after two years. The rubber from second-year plants is

generally an improvement on firstyear rubber in both quantity and quality.” In an article in the Australian Journal of Science, Professor A. E. V. Richardson writes : “In Russia Kok-saghyz is sown from seed in the spring (March-April) in rows 15 to 18 inches apart. The methods of cultivation followed are somewhat similar to those employed for sugar beet. It is generally harvested in the first autumn (October), but frequently left for a second year and harvested in the summer.” “ . . . average yields in the Soviet Union are said to be about 1| tons of raw roots in the first season.

The rubber content of the raw root appears to be variable and to range from 2to 4 per cent. If the crop is left for the second season the percentage of rubber in the roots increases and the yield of rubber per acre is higher.” Again, Dr. Paul Kolachov in a bulletin published by the National Farm Chemurgic Council of the U.S.A, states: “If the crop is harvested at the end of the first year, Kok-saghyz plants yield an average of 4500 to 5500 pounds of cleaned roots per acre, which equals 150 to 200 pounds of crude rubber, and 75 to 100 pounds of seed. If the crop is left for a second year, the average yield is 2700 to 3600 pounds of root and from 100 to 150 pounds of seed. In

some cases the yield at the . end of the first year is as high as 7000 pounds of root, which, of course, . gives an even larger amount of crude rubber, At the end of the second year, the percentage of crude rubber is higher, but the yield of 16 roots is less, since 16 plants have been thinned out by the frosts of the preceding winter, have been attacked by rodents, and the roots have been spoiled by their tendency to work up through the crevices in the soil.” In regard to processing, Richardson states that this is done by slicing and steaming the partly-dried raw material with dilute' caustic soda solution added and separating the rubber by flota-

tion or centrifuging, while the Imperial Bureau writer says that it. is sufficient to reduce the roots (presumably dried) to a fine powder which is macerated with water when the rubber separates out from the other matter by gravitation.

All writers are agreed, however, that the plant is highly adaptable as to soil and climate. It is cultivated from the South of Russia to the Arctic Circle, on alkaline soils, peats and podzols. On very acid soils liming is necessary. Best results are secured from rich soils, and a somewhat complicated manuring programme has been developed in the Soviet Union in order to obtain maximum yields. Good soil moisture conditions and a rainfall of over 20 inches chiefly in spring and autumn, are necessary. As grown commercially, Kok-saghyz is at present little different from the original wild plant. It is extremely variable, and plant breeders have already made considerable progress in the task of creating a type more suitable for cultivation, with larger roots and higher rubber content. Possibilities in N.Z,. It would appear that this crop offers possibilities for cultivation within the range of our climate and soils, and is probably the only means within sight for the short-term production of rubber in New Zealand. Every endeavour has been made to secure seed, and through the courtesy of the Australian Government sufficient for experimental purposes is expected to arrive shortly. The first consignment has now been received. Some seed has already been sown in Australia. In the first instance plots will be established in various parts of New Zealand in order to secure data regarding environmental and cultural requirements, yield of rubber at various, stages of growth, methods of processing, and production and viability of seed. If successful, seed stocks will be built up and no doubt a programme of plant breeding initiated. This investigation is being conducted jointly by the Department of Agriculture and the Department of Scientific and Industrial Research. The botanical side is under the charge of the Botany Division, Scientific and Industrial Research, while field plots will be established by the Fields Division of the Department of Agriculture. Rubber analyses and processing trials will be carried out in the Chemical Laboratory of the latter Department if and when roots are grown. The accompanying illustrations are from “Kok-saghyz” Family Compositae, as a Practical Source of Natural Rubber for the United States,” published by the National Farm Chemurgic Council.