oils, and others are also used as carriers for other herbicides. Oil sprays are usually 

 more effective than water sprays in wetting leaf surfaces and in penetrating waxy leaf 

 surfaces. 



CHLORATES 



A number of chlorates, including calcium and sodium, are used to control deep-rooted 

 perennial weeds, and for temporary and semipermanent soil sterilization to prevent 

 the growth of all types of vegetation. Sodium chlorate, a white crystalline water- 

 soluble powder, is used most extensively. It can be applied in dry form by hand or with 

 various types of spreaders, or as a spray using high-volume spray equipment. 



For semipermanent soil sterilization in humid areas, 800 to 1,900 pounds of sodium 

 chlorate per acre (5 to 12 pounds per square rod) are required; in senniarid areas, 

 500 to 1,000 pounds per acre (3 to 6 pounds per square rod) are required for semi- 

 permanent soil sterilization. However, higher rates may be required to kill certain 

 perennial weeds under some conditions. Sodium chlorate leaves the soil unproductive 

 for a period varying from 1 to 4 years depending on the precipitation, prevailing tem- 

 peratures, soil type, and other soil and climatic factors. On sandy soils of humid 

 regions higher rates are required for residual sterilization than on the heavy soils 

 under lower rainfall conditions. In the arid regions on heavy soils, higher initial rates 

 of application are required to kill all vegetation, but the residual toxicity persists for 

 longer periods due to less leaching and slower decomposition than normally occur 

 under humid conditions. 



Caution. Sodium chlorate, particularly in spray solutions, nnust be handled with 

 extreme caution. Any inflanamable materials, such as clothing, shoes, hay, wood, or 

 weeds, that have dried after having been wetted with a sodium chlorate solution be- 

 come violently inflammable and even explosive. They can be easily ignited by 

 friction, sparks, or even by the heat from the sun. Serious injury or property 

 damage may result from carelessness or failure to observe this precaution. The 

 manufacturer's instructions for the use of this chemical should be followed carefully. 



BORON COMPOUNDS 



A number of boron compounds, including borax, sodium pentaborate, boron trioxide, 

 anhydrous sodium biborate, and mixtures of these compounds with 2,4-D and/or sodium 

 chlorate are used to control deep-rooted perennial weeds, and for tennporary and 

 semipermanent soil sterilization to prevent growth of all vegetation. Boron compounds 

 should be applied at rates of 2,400 to 4,800 pounds of borax equivalent per acre (15 to 

 30 pounds per square rod) for the control of all vegetation and semipermanent soil 

 sterilization in humid areas; in arid regions the rates required are usually higher-- 

 4,800 to 6,400 pounds per acre (30 to 40 pounds per square rod). The addition of 2,4-D 

 or sodium chlorate to boron compounds will greatly influence the rate of application re- 

 quired for killing all vegetation. Boron compounds are normally applied as dry granular 

 formulations, but nnixtures of boron and 2,4-D, and boron and sodium chlorate, are 

 also formulated for spray application. 



ARSENICALS 



Arsenical herbicides include sodium arsenite, arsenic trioxide, arsenic pentoxide, 

 and other formulations of arsenic acid. They are highly poisonous to animals , and for 

 this reason have not been used widely as herbicides on agricultural lands. Sodium 

 arsenite (the most commonly used arsenical) is used extensively to kill submerged 

 aquatic weeds, and as a semipermanent soil sterilant to control all vegetation on 

 driveways, tennis courts, railroad rights-of-way, industrial storage sites, and on other 

 nonagricultural areas inaccessible to animals. It leaves the soil xinproductive for 1 to 

 4 years, depending upon the soil type and climatic conditions. 



