290 • COBN CROPS 



219. Effect on the land. — The sweet sorghums sown 

 thickly have the reputation of being " hard on the land." 

 Grain sorghums planted thin seem to have the same effect 

 also, in lesser degree. All millets have the same reputation. 

 No very satisfactory explanation for this has been ad- 

 vanced. When the effect is noted it is most marked on the 

 first crop following, and less marked afterward, usually 

 completely disappearing in one or two years. The effect 

 is most marked on small grain and less on intertilled 

 crops. 



As the sorghum roots are rather concentrated in the 

 upper layers of soil, it is possible that this soil is very much 

 exhausted of available fertility. There is some reason to 

 believe that sorghums may exhaust available fertility to 

 lower limits than do other crops. It is not known whether 

 sorghums have a toxic effect on the soil. 



The injurious effect when noted is considered only 

 temporary, and farmers in general do not consider it a 

 serious drawback to sorghum culture. 



220. Alkali resistance. — Sorghum is often said to be 

 alkali-resistant. It is not resistant in the same sense 

 as are many native alkali plants, but at least it is one of 

 the best of our cultivated plants to succeed on land rich 

 in alkali. 



SOKGHUM TYPES 



221. A common grouping, based principally on the 

 economic use of the crop, is (a) Saccharine sorghums, (b) 

 Non-saccharine sorghums, (c) Broom-corns. 



A. Saccharine sorghums. Those having an abundant sweet 

 juice. Cultivated at one time principally for sirup manu- 

 facture, but now principally as a forage plant. Commonly 

 known as " sorghum." I. Sorgo. 



