134 



THE INDIA RUBBER WORLD 



[Decemder 1, 1916. 



■roKi 'Guayiitt 



< li. Lloyd. 



Average Minimum 



in rubber, if his figures can be substantiated, is of great interest. 

 The conservative estimate, by the way, is 8 to 10 per cent. 



De Kalb further states that by four-year intensive irriga- 

 tion methods. 25 tons of dry plant may be grown per acre. On 

 the basis of 8 per 

 cent rubber this 

 would yield 4.a)0 

 pounds, wort h 

 $1,520. according 

 to the present 

 low market price 

 ol 38 cents per 

 pound. American 

 experience places 

 the average cost 

 of culture, har- 

 vesting, extrac- 

 tion and market- 

 ing at $200 an 

 acre annually, or 

 $8(10 for the crop. 

 Tliis makes the 

 net income $720 

 an acre or $180 

 an acre per year. 

 Few crops surpass 

 this on an aver- 

 age of four con- 

 secutive years, 

 and what can be 

 grown on arid soil which will approach so high a return? .Assum- 

 ing that 5.000.000 acres of irrigable land, still unutilized, could be 

 devoted to this purpose, the yield would be 10,000,000 tons for 

 the four years, equivalent to 2,500,000 tons aiuiually and worth 

 $8,500,000,000. 



Once more, what of the 455,000.000 acres of arid agricultural 

 land not capable of irrigation? If planted with guayule and 

 liroperly conserved according to the principles of modern for- 

 estry, they would 

 create a great 

 new A m e r i can 

 industry that 

 would be a source 

 of wealth in time 

 of peace and a 

 protection in case 

 of war. Fifteen 

 years is consid- 

 ered the proper 

 rotation period, 

 as in that time 

 the maximum 

 economic efficien- 

 cy of the plant 

 is reached at a 

 height of about 

 16 inches, when 

 it should be le- 

 moved, not only 

 for the better 

 growth of young- 

 er plants, but for 

 the greater effi- 

 ciencv of seeding. 



.\ND M.xxiMUM Seedlings 



Frotn "Guavule.' 



By Francis E. Lloyd. 



Irrig.vted Pl.\nt, Two Years Old, From a Stock 



Thus cuttings should be made close to the ground every fifth 

 year. The old practice of pulling plants up by the roots is to be 

 discouraged as it gives no opportunity for new shoots to be sent 

 up during the next growing season. 



Assuming 11,200 plants to the acre and each dry plant aver- 



aging 1 pound at 15 years, the yield would be 5 tons of shrub per 

 acre, or 896 pounds of ruliber on an 8 per cent basis. Were 

 455.000,000 acres so planted the yield would be 182,000.000 tons 

 every five years, or an average of 36,400,000 tons annually, worth 



$154,700,000,000 at 

 tile current price 

 of 38 cents per 

 pound. Thus, the 

 L'nited States is 

 potentially able 

 to provide with- 

 in its own bor- 

 ders many times 

 its own require- 

 ments of crude 

 rubber. 



Reviewing the 

 history of guay- 

 u 1 e extraction 

 the following 

 points are of in- 

 terest: The nat- 

 ural habitat of 

 the shrub em- 

 braces the north- 

 ern portion of 

 the great central 

 plateau of Mex- 

 ico, known as the 

 Chihuahuan des- 

 ert, and a portion of southwestern Texas, an area of nearly 

 1.30,000 square miles, of which about 34,000 square miles ac- 

 tually bear guayule. From this source it has been estimated 

 by Endlich that 225.000 tons of shrub had been disposed of 

 up to 1909, which was about half the total supply originally 

 available. The altitude of this region varies from 2,000 to 

 10,000 feet above sea level, the average being 6,000 feet, for 

 guayule can withstand very low temperatures as well as summer 



heat. The records 

 include 5 degrees. 

 F. at Marathon, 

 Te.xas, and 10 

 degrees F. at 

 Tucson, Arizona. 

 Very little rain- 

 fall is necessary, 

 the average 

 throughout this 

 region being 

 around 10 inches 

 annually, al- 

 though the 

 growth of the 

 l)lant is in pro- 

 portion to the 

 precipitation. The 

 plant grows dur- 

 ing the rainy-sea- 

 son and creates 

 rubber during 

 the dry. months, 

 the residual soil 

 moisture, except 

 in rare instances, 

 being sufficient to sustain lite. Maximum growth occurs early 

 in the warm season, when superficial soil water is most plentiful 

 and night and day temperatures are more nearly uniform. The 

 humidity of the region is relatively high, with a somewhat pro- 

 longed summer period of high humidity. Dew is frequent during 



