156 The Commercial Apple Industry 



tern has come into common use. Alfalfa seems best suited / 

 to the irrigated orchard land of the West and although it 

 is spoken of there as a cover-crop, it is more properly either 

 an inter-crop or a sod-mulch, for it remains in the orchard 

 for several years and as a rule one or two cuttings are taken 

 off in the form of hay. 



CLEAN CULTIVATION 



Clean cultivation has many evils which are not at once 

 apparent. The most striking example occurred in the 

 Hood River Valley, Oregon, where clean cultivation was 

 practiced until about 1915 when the bearing orchards 

 began to show marked signs of lack of vigor, evidenced by 

 \pale foliage, light yields of small fruit and poor annual 

 growth. The Hood River orchards made a marked recov- 

 ery in the next two or three years, following wider use of 

 irrigation in growing leguminous cover-crops and on appli- 

 cation of nitrate of soda. 



Except in special cases, continued clean cultivation can 

 have only disastrous results. Where there is sufficient 

 nitrogen and humus in the soil, there is no particular 

 objection to clean cultivation for a limited period of years. 

 Clean culture for a time unquestionably stimulates tree 

 growth and increases yields. It has been observed that 

 this practice is followed continuously in some of the best 

 paying and finest apple orchards in the United States. 

 Invariably, however, in such instances the original soil was 

 unusually rich in humus and other plant-food and this J 

 reservoir has not been exhausted. It is better to maintain 

 fertility, for once depleted its restoration is difficult. 



In starting young orchards, clean cultivation is not y 

 harmful for the first three or four years. In fact, it may 



