144 Report of State Board of Horticulture. 



more. This oxidization and aeration are highly important processes 

 in the biological functionings of the soil, and most useful factors in 

 rendering the plant food of the soil available for tree growth. 



COVER CROPS. 



This is a phase of orchard management that has received little 

 attention as yet. Speaking more particularly of Western Oregon it 

 may be said: Thus far our orchards that are thoroughly tilled have 

 shown no especial need of Service in the directions in which a Cover 

 crop would aid them, but the time is approaching when such conditions 

 will no longer exist. Thorough tillage increases oxidization in the soil. 

 The humus burns away, as it were, and need for material to replace 

 the original supply will be manifest, in a dryer, harsher soil, some- 

 times heavier, sometimes lighter; in a soil that will be cloddy and 

 intractable, generally throughout Western Oregon. This material can 

 be obtained at least expense by means of cover crops, as oats, wheat, 

 rye, vetch, clover, mustard, and the like. 



As to the functions of a cover crop altogether, it may be well to 

 quote from bulletin No. 61, of the Delaware Station, which says: 



" WH AT DOES A COVER CROP DO? 



1. If sown at the proper time, about August Ist if weather con- 

 ditions are favorable, it competes with the trees for soil moisture and 

 plant food. The supply of moisture and food to the trees is lessened 

 and their growth is checked. This is desirable, because at that time 

 the trees should stop growing and ripen their wood for the winter;* 



2. It Catches soluble nitrates late in the fall when root action of 

 the trees has nearly or quite ceased, thus much plant food is saved 

 rather than allowed to escape in drainage; 



3. It prevents erosion of the surface soil by catching the rains 

 as they descend and by conducting them into the soil. This is in 

 contrast to streams of water flowing over the bare surface and cutting 

 Channels for the escape of surplus water. It also holds the snow of 

 Winter, which adds to the efficiency of the protection; 



4. It protects the ground from frost to a certain extent; that is, 

 actual tests have proven that ground protected by live cover crops 

 during the winter does not freeze so deep as does bare ground; 



5. In the spring it catches soluble nitrates that might leach out 

 of the soil before active root action of the tree begins; 



6. It pumps the surplus water out of the soil early in spring so 

 that the ground warms up and may be plowed earlier than if no 

 Cover crop were used; 



7. When plowed under, these crops add enormous amounts of 

 vegetable matter or humus to the soil. The humus improves the 

 mechanical condition of the ground by loosening up the soil particles; 

 it increases the water-holding power of the soil, provides a favorable 

 home for soil bacteria, furnishes elements of plant food in available 

 form, and assists in breaking up chemical Compounds of plant food 

 which would otherwise remain unavailable; 



8. Experience has shown that the continued use of cover crops 

 will, to a certain extent, make heavy land lighter and light land heavier. 

 This is an immense advantage in practical orchard Operations." 



Cover crops may be grouped into two — possibly three — classes; the 

 leguminous, as peas, beans, alfalfa, clovers, vetches, cow peas, and the 



*This Statement applies more particularly to young trees. Bearing trees 

 with US would need no such check and It would be well to sow the cover later, 

 thus not shorten ng the supply of water for the fruit. 



