266 SOILS. 



Mulching. Covering the soil with straw or similar loose 

 materials to prevent waste of moisture is a common garden 

 practice everywhere, although not usually applicable on the 

 large scale. It may readily however, be carried to excess, in 

 preventing not only evaporation but also the warming of the 

 soil which is so needful to the thrifty growth of plants. It 

 must not therefore be done too early in the season; and after 

 cold rains it sometimes becomes necessary to remove the mulch 

 in order to allow the ground to become properly warmed. 

 Mulching in early spring is often used to retard blooming of 

 trees where spring frosts are feared. 



In the arid region, sanding of the surface is sometimes re- 

 sorted to for the prevention of the evaporation which brings 

 alkali salts to the surface. But the necessity of repeating this 

 dressing annually unless cultivation can be omitted, restricts 

 the use of this expedient to narrow limits. 



The sanding of the surface of cranberry plantations in 

 swamps or bogs in the northern parts of the humid region 

 doubtless owes its efficacy largely, if not chiefly, to the re- 

 tention of moisture, while at the same time it prevents the con- 

 solidation of the surface, so as to render tillage unnecessary. 



