SELECTION OF SITE 9 



Thus the finer these soil particles the greater the number of 

 films, resulting in a larger amount of moisture in a given soil. 

 Drainage does not remove this film moisture. It is only re- 

 moved through the growing plant by transpiration and by evapo- 

 ration from the surface of the soil. The latter may be controlled 

 by proper tillage or soil-mulch conservation. 



The humus content of a given soil is another important re- 

 quirement in regard to the water supply in the soil. The supply 

 of humus in the soil, generally included in the surface layer, 

 greatly lessens the loss of moisture by evaporation, and further 

 increases considerably the moisture-holding capacity of the soil, 

 both as to rainfall and the rise of capillary water. Hence the 

 greater the amount of moisture in a soil, the lower the tempera- 

 ture of that soil during the summer. 



Closely connected with the texture and the humus content of a 

 soil in regard to the water supply is the degree of soil tilth. The 

 more complete the mulch formed by cultivation, the greater the 

 conservation of soil moisture ; or, in other words, the loss by 

 evaporation is materially lessened where good tillage is practiced. 



Surface, drainage, air, and water. It is essential that some 

 elevation be given to the site for an orchard, in order that good 

 air and water drainage may be obtained. Cold air, being heavier 

 than warm air, has a tendency to flow or run downhill, while the 

 warmer air will rise. This flow, or free movement, of the air is 

 obtained if an elevation is selected as a site for an apple orchard. 

 Often an elevation of not more than from fifty to one hundred 

 feet will be sufficient to give this action, particularly if there is a 

 good outlet, such as a water channel, below ; but if a pocket is 

 formed and the cold air is retained, as in valleys and such places, 

 the location is not desirable, owing to the fact that on still, clear, 

 cool nights frost is likely to occur and great injury may result. 



Besides the desirable air drainage, water drainage will be given 

 on these elevated sites, doing away with the injury of standing 

 water around the roots of the trees. Nevertheless, washing of the 

 soil should be avoided by the selecting of gradual slopes, the planting 

 of cover crops, or other means. 



