No. 6. DKPAKTMENT OF AGKlCUl/rURE. 343 



Ajjplicatioii of lime for the purpose of bringing; aboiil I lie im- 

 provement of these physical oonditions have been found in some 

 eases to j'ive excellent results, especially on heavy clay soils. The 

 binding action of lime is well known. Lime will cement the small 

 particles of a clay soil at the surface, forming larger pores, thus 

 rendering such a soil more pervious to water, and in many cases 

 prevent washing. 



Again, imderdrainage is often an important factor in increasing 

 the ability of the soil to absorb and retain moisture. The fact has 

 already been noted that the presence of free water, within a certain 

 distance of the surface, is injurious to plant life. Underdrainage 

 lowers the level of this free water, where it exists, and prevents the 

 baking and cracking of the surface which occurs when a water- 

 logged soil dries out; it renders the soil above more friable and 

 loose, therefore, more adaptable as a home for plants. The soil 

 that can better absorb water, capillary action can go on more readily 

 and water can reach the rootlets witli more ease. 



Concerning the losses of moisture, which occur subsequently to its 

 absorption by the soil, evaporation is chiefly responsible. It has 

 already been noted how the particles of soil form capillary tubes 

 through which water is lifted from underneath to. the surface. At 

 Syracuse, New York, a test was made by the Government in con- 

 nection with the salt works in that city to ascertain the rate of 

 evaporation as compared with the amount of rainfall. The evapo- 

 ration from a water surface in a year was 50.2 inches, while during 

 the same period the rainfall amounted to 41.47 inches. From this 

 i( can be readily seen how rapidlj^ under favorable conditions, 

 (naporatiou may occur from the soil where there is a much larger 

 surface exposed. To prevent evaporation from a vessel contain- 

 ing water, it is necessary to cover it, and on the same principle to 

 prevent unnecessary evaporation from the soil, it is necessary t<) 

 place a check at the surface of the ground. Our homes may be 

 supplied with water from a mountain spring or from reservoirs. 

 The water is conveyed by means of pipes into our houses. The sup- 

 ply, however, is controlled by valves. The water is at our very 

 hand; all we have to do is to turn the valve. This prevents the 

 great waste which would occur did the water run continuously, 

 The same principle applies to the feeding of plants with water in 

 the soil. We have the supply or reservoir deep in the soil. Through 

 capillary action it is brought within reach of the rootlets and even 

 to the surface where it escapes by evaporation. Nov/ to prevent 

 this waste it is desirable to put a valve at the surface; to have the 

 moisture come so far and then prevent, so far as possible, its es- 

 cape. Surface cultivation accomplishes this, breaking the capil- 

 larv tubes and forming a mulch which arrests evaporation. Now, 



