weeds. Application should be made in early spring or fall. Effects of the 

 chemical rennain in the soil for only a few weeks after treatment. 



Chloro Substituted Benzoic Acids 



2,3.6-TBA at 15 to 20 pounds or PBA at 35 to 40 pounds per acre will 

 control bindw^eed. Higher rates may be required for control of additional 

 species of herbaceous perennial weeds. These rates of application sterilize 

 the soil temporarily and investigations are continuing to determine the 

 cultural and rotational practices that must acconnpany their use. 



Soil Sterilants 



For control of deep-rooted broadleaved species in small patches in culti- 

 vated fields: Soil sterilants, such as sodium chlorate, borax (or mixtures 

 of these two), and erbon. Sodium chlorate should be applied at 3 to 10 pounds 

 per square rod (480 to 1600 pounds per acre), borax at 15 to 40 pounds 

 (2400 to 6400 pounds per acre), and mixtures at 6 to 20 pounds, Erbon should 

 be applied at 80 to 160 pounds per acre. Surviving plants should be treated 

 again in subsequent years. 



PERENNIAL GRASSES, RUSHES, AND NUTSEDGES 



Perennial Grasses 



Cultivation and combination of herbicides . - -Johnsongrass, Bermudagrass, 

 and quackgrass can be controlled by repeated intensive cultivation which 

 prevents top growth and destroys food reserves in the roots. Intensive 

 cultivation is most effective under dry weather conditions, but with ample 

 soil moisture to promote active grow^th from roots and rhizomes. 



The anaount of cultivation needed for control can be reduced by applying 

 TCA at 25 to 50 pounds or dalapon at 10 to 20 pounds per acre as a foilage 

 and soil surface treatnnent 1 week before plow^ing or disking in late fall or 

 early spring. Cultivated row crops should be grown the first year following 

 these treatments to insure continued control by frequent general cultiva- 

 tion, spot cultivation, or herbicide application. A strongly competitive crop 

 limits w^eed growth by shading and competition for moisture and nutrients. 



Pre-planting treatments . --(1) For control of quackgrass: A fall or spring 

 application of 2 to 4 pounds of simazine or atrazine in 20 to 40 gallons of 

 •water per acre has proved effective w^hen follov/ed by plow^ing or cultivation 

 before planting corn. 



Spring application of dalapon at 4 to 5 pounds in 20 to 40 gallons of water 

 per acre when quackgrass is 4 to 10 inches tall followed by plowing in 1 week 

 reduces the stand and vigor of this grass. Planting of corn should be delayed 

 for 4 weeks after treatment. 



In humid regions, early spring foliage applications of 4 pounds of MH, 

 followed in 4 to 8 days by plowing, has given effective control. MH does 

 not leave a toxic residue in the soil and crops may be planted as soon as 

 soil preparation is completed. 



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