PREFACE 



For about thirty years Johnson grass has s;)rea(l, at first slowly and 

 then with increased rapichty. at altitudes of -lOOO feet and below, 

 throughout Arizona. In some cases its introduction was no doubt acci- 

 dental : liut in other instances it is known to have been planted by 

 irrigatiui^ farmers as a ha)- crop, and by stockmen as an emergency 

 forage. Johnson grass is therefore now well distributed over grazing 

 ranges, along" water courses, and throughout the lower irrigated valless 

 of the State. W hile this plant, with its tk'shy rootstocks, may serve 

 beneficially as an emergency forag;e, and as a soil binder to prevent 

 erosion, its main effect is as a j^estiferous weed in irrigated valleys, 

 l)reventing- the profitable culture of simimer cro])s and depreciating land 

 values seriously. 



The State has endeavored to regulate this weed by means of a law- 

 prohibiting all traf^c in Johnson grass plants and seed, or its culture, 

 but with little effect upon the pest. 



Many attempts have been made by the farmers themselves to exter- 

 minate or control Johnson grass. Continuous dry fallowing of infested 

 fields is jiracticed ; sheep are to some extent being used along ditches 

 and weedy roadsides ; and "easy methods" of soil treatment by chemicals, 

 steam, or otherwise, have been proposed ; but more and more it is being 

 found that intelligent and persistent cultural methods base<l on a knowl- 

 edge of the plant and the effective use of crop rotations, are most cer- 

 tainly successful. Intensive cultivation of valuable summer growing 

 crops, such as cotton and Indian corn, is perhaps the most effective 

 means of disposing of Johnson grass, seconded by winter growing crops 

 of grain, lettuce and various vegetables. 



Not only may Johnson grass be effectively and economically con- 

 trolled by cultural methods, but a benefit may be derived from it, inas- 

 much as it is observed that old Johnson grass land enriched with 

 ([uantities of organic matter derived from decayed rootstocks is more 

 productive than ordinary soil. In 1917, 41 to 50 bushels of wheat per 

 acre were growMi at the Salt River Valley farm on land that had been 

 badly infested with Johnson grass. 



It may be, therefore, that Johnson grass, like some other ai)parcnt 

 misfortunes, handled with energy and determination, will ])rove a 



blessing in disgtiise. 



R. IT. FoRRKs, 



Director. 



