SUGGESTIONS TO SETTLERS IN COLUMBIA RIVER VALLEY. 19 



would otherwise be bare. When they have served their special pur- 

 pose, cover crops are often turned under as green manure. 



Plants that have }>ea-like flowers and usually produce their seed 

 in two-valved pods, such as peas, beans, vetch, clover, and alfalfa, 

 are called legumes. If thrifty plants of this family be carefully 

 removed from the soil, little nodules will usually be found upon their 

 roots. These nodules vary in si^e with different legumes and may be 

 found alone or in clusters. They are caused by certain bacteria of the 

 soil that become parasitic in the roots. 



By the aid of these bacteria living in the nodulc^s, leguminous plants 

 are enabled to assimilate the atmospheric nitrogen. Since nitrogen 

 constitutes approximately four-fifths of the atmosphere, this family 

 of ])lants has an inexhaustible supply of this important plant-food 

 element. If the nodule-forming bacteria are not present in the soil, 

 the nodules will not form on the roots, and the plants can then use 

 only the nitrogen of the soil. The failure of leguminous crops is 

 sometimes due to the lack of these bacteria. 



Nodule-forming bacteria may be supplied in two ways, namely, by 

 the use of pure cultures of the bacteria and by transferring soil from 

 a field where the crop to be used has been grown successfully with 

 nodules on the roots. From 200 to 300 pounds of the soil transferred 

 are scattered over each acre of the field to be inoculated and imme- 

 diatc^ly mixed with that of the new field by plowing, disking, or har- 

 rowing. If left exposed to the sun the bacteria are soon destroyed." 



It has been pre\aously pointed out that the soils along the Columbia 

 River are very deficient in humus and nitrogen. It is very evident, 

 therefore, that the farmers and orchardists of this region should use 

 every possible opportunity to grow humus-forming crops. Because 

 of their ability to use the nitrogen of the atmosphere, leguminous 

 crops should be used when possible. The ground should not be 

 allowed to lie idle, but as much of the time as possible it shoidd be 

 kept growing some crop that will improve the soil. 



CROPS TO USE. 



The following green-manure and cover crops are recommended: 

 * (1) For permanent crops in the orchard use red clover or alfalfa. 

 ^^'^lere it is not necessary to give the orchard clean cultivation in 

 order to conserve moisture, perhaps no better practice can be followed 

 than to grow red clover or alfalfa between the trees. While orchard 

 cover crops are often used for hay the land will be improved much 

 more rapidly if the growth is clipped five or six times during the sea- 

 son and left on the ground to serve as a mulch. "VMiere it is desirable 



n For information re<];arding the use of pure cultures of the bacteria, see Farmers' 

 I'.uUetin 315, entitled "Progress in Legume Inoculation," which will be sent free of 

 I harge upon application to the Secretary of Agriculture, Washington, D. C. 

 [Cir. 60] 



