LUTHER BURBANK 



The effects of rotation are most astonishing as 

 shown by the results attained especially in Cali- 

 fornia when grain follows a corn crop. There is 

 usually fully twice the yield secured from the 

 small grain crop following a crop of corn than 

 when small grain follows a crop of small grain. 



No doubt, the cultivation given the corn during 

 the summer has much to do with putting the soil 

 in the proper physical condition for plant growth. 

 This cultivation destroys more of the microscopic 

 organisms which are injurious to plant life, and 

 releases elements which otherwise would be 

 unavailable. 



With the present varieties of plants, it will 

 probably always be necessary to practice rotation 

 of crops. But when plants are developed which 

 are resistant to the various conditions which have 

 been mentioned, rotation will perhaps not be so 

 necessary. 



Already certain plants have been developed 

 which are resistant to numerous diseases and 

 insects. Varieties of grapes are grown which re- 

 sist the attacks of phyloera, and apples which are 

 resistant to the attacks of aphis are well known. 



Peaches and almonds which are not subject to 

 curl leaf have been developed. 



Plums which are not affected by the brownrot 

 and plum pocket are now on the market, also 



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