Vol. XVII. No. 425. 



THE AGRICULTURAL NEWS. 



THE SUCCESSFUL CULTIVATION OF 



GUAYULE. 



What is known as guayule rubber is the product of 

 a shrub not more than 2 or 3 leet high, which grows abund- 

 antly in some of the desert regions of Mexico. This shrub 

 is known botanically as Partlu iiiiim argtiitatum, of the same 

 genus as the common West Indian weed known in many of 

 these islands as 'white head', which is P. Hyslcrophonis. The 

 guayule shrub is the only member of the (i'ompositae which 

 contains India rubber in sufficient .juantity for commercial 

 exploitation. Indeed the contents of rubber in Pirthenium 

 argentatum is so gieat that this plant is the richest in yield 

 of all known rubber-bearing plants, the average content of 

 pure rubber substance being from 8 to 10 per cent, on the 

 dried plant material. In the later years of the nineteenth 

 century companies were formed for the exploitation of this 

 product in Mexico. The largest of these was an American 

 concern; and the story of how this American company has 

 attained remarkable success in gilayule cultivation is a strik- 

 ing instance of what was pointed out in the editorial of the 

 last issue of this Journal, namely the benefit to be derived 

 by agriculturists from the researches of plant physiologists 

 and other scientific men. 



This story appears in an article by Mr. Henry C 

 Pearson in the India Ruhbo- //'(;;-/(/, July 1, 1918, from 

 which the following paragraphs are chiefly compiled. 



To those in charge of the American concern referred to 

 above, it was perfectly apparent ten years ago that the time 

 would come when the wild guayule fields would be exhausted, 

 and the business be either entirely stopped or shut down 

 until new plants matured. No one knew whether regrowth 

 could be induced, or whether the shrub could be raised from 

 seed or cuttings. In fact most people believed that the 

 plant would never yield to profitable cultivation. 



The head of the company set about solving the problem 

 in the right way, and here is the interest of the story. The 

 first thing done was the selection of a corps of chemists, 

 botanists, plant physiologists, and experts in desert 

 plants. For this purpose men were obtained from agri- 

 cultural colleges, desert laboratories and experiment stations, 

 and arrangements were made to send their notes and 

 observntions to seats of botanical learning, so as to obtain 

 accurate conclusions on the subjects investigated. The 

 following pi lints in relation to the plant were examined most 

 thoroughly; the geographical and altitudinal distribution, 

 climate, air and soil temperature, rainfall, soil moisture and 

 relative humidity, analysis of soils and of plants under all 

 conditions. The seeds, leaves, flowers, stems, and roots were 

 ■scrutinized under the effects of dispase, drought, rain, and 

 irrigation. 



In time the work begun in Mexico was transferred to 

 California and Arizona, where laboratoiies and experimental 

 plants were establi-shed, and the work on a commercial scale 

 actually commenced. But before this took place the plant 

 may be said to have been practically remade by science. 



In the first place, tl e wild plant of the desert yields very 

 few good seeds. As plenty of vital seed is an essential for 

 extended cultivation, the plant physiologists planted the 

 guayule under all kinds of conditions, until positive knowledge 

 was gained what treatment was necessary to obtain plentiful 

 seeds. There was another difficulty in connexion with the 

 seeds of the wild plant. .Although the seeds appeared to be 

 perfect, very few could be induced to germinate. It may be 

 mentioned that of seeds of the guayule obtained by the 

 Imperial Department of Agriculture for the West Indies from 

 Mexico somf time ago, and .li&tributed for trial among eonie 



of the Botanic Stations in these islands, not one germinated. 

 In the experiments now being described the same thing hap- 

 pened. Of a bushel of seed first planted most carefully not 

 one grew. For a long time only failure resulted in this 

 direction, although small lots of seed were sown under every 

 imaginable condition, and the problem was only solved by 

 what Mr. Pearson calls an accident. 



Another difficulty in profitable cultivation of guayule 

 was the question of its slow growth. Under desert conditions 

 in its original habitat the plant takes some twenty years to 

 arrive at maturity. It only grows a little at one season in 

 each year. The plant physiologists however took advantage 

 of this habit of a slight growth in the spring, and furnished 

 the plant, so to speak, with simulated springs, so that before 

 it could settle back for months to rest, the plant began grow- 

 ing again. By this method the shrub was induced to attain 

 its full growth in four years. 



The study of the varieties of the guayule led to most 

 .satisfactory results. The plant physiologist, to whom this 

 investigation was entrusted, states that he had observed more 

 than 900 ditJerent types of the plant. An analysis was 

 undertaken in the first place to ascertain the difference in 

 the amount of rubber in the different types. This was shown 

 to vary from 1 per cent, to as high as 20 per cent., and some- 

 times even to 27 per cent. The poorer varieties were 

 eliminated, and those that produced the largest percentage 

 were selected as seed bearers. 



Guayule rubber was not at first considered to be of the 

 highest grade. When it first came upon the market its 

 resin content was so high, and it was so soft, that it was 

 accepted with reluctance. The plant physiologists, how- 

 ever, when they began to test the quality of the 

 rubber in different plants, found out some more secrets. 

 .Some of the types gave simply a black resinous paste that 

 did not contain enough rubber for extraction. Others con- 

 tained rubber with about 20 per cent, of resin, the kind of 

 rubber familiar to dealers in the guayule product. A few, 

 however, yielded a firm, hard product eijualling the best 

 rubber. In this case also the types producing the best rubber 

 were planted as seed bearers for cultivated guayule. As a 

 final result, by hybridization of the types producing the 

 largest quantity of rubber with the types producing the best 

 quality, plants were obtained having the good points of each, 

 so that at length the real cultivation of guayule was 

 demonstrated to be feasible 



The growing of India rubber, particularly the tapping of 

 the trees and gathering of the latex is entirely done by hand 

 in the great plantations of the Fast. In the cultivation and 

 collection of guayule, however, machinery takes the place of 

 men. The preparation of the fields is done by disc harrows 

 drawn by tractors. The planting is done by specially built 

 machines which plough four furrows, set the plants at the 

 proper intervals, cover them in, and pack the earth about 

 the roots. One machine plants 18 acres a day. The culti- 

 vation is also done by machinery. For gathering, there are 

 two systems: in one, the rows are cut down by a reaping 

 machine; in the other, the plant is p'oughed out root and all. 

 The extraction of the rubber is also, of course, wholly 

 mechanical. 



Guayule growing in a large plantation involves a labora- 

 tory for examining and testing the plant and the product, 

 a green house for seed experiment and hybridization, out-door 

 plants for seed bearing, seed beds protected by wind-breaks, 

 machinery for planting .ind harvesting, an extraction plant, 

 and plenty of capital. As an example of beneficial co opera- 

 tion between science and practice, the successful cultivation of 

 the guayule plant is a striking one. 



