466 MINNESOTA STATE HORTICULTURAL SOCIETY. 



dry surface orders an invoice from the .c;round water beneath. The 

 draft is honored, and capillarity is the water bearer who delivers it 

 as directed, but the treasure is immediately seized by the wanton 

 wind, and the loss cannot be repaired. This process is continually 

 repeated till the earth becomes dry to a point which the plant roots, 

 with all the aid they can get by capillary attraction, cannot reach ; 

 so the leaves dry up, and the crop fails unless timely rains come to its 

 relief, which at this season of the year we are not warranted in ex- 

 pecting. What shall be done? The pumping up process must con- 

 tinue; the crops demand it — in fact, it is a matter of life or death 

 with them. But they and not the surrounding atmosphere must 

 have the benefit. 



Evaporation then or, at least, the larger part of it must be 

 stopped, and the plant roots must have a chance to utilize the moist- 

 ure heretofore wasted. This is no chimerical idea, as it has been suc- 

 cessfully practiced in the semi-arid lands of Washington for several 

 years, and the system is now firmly established. In the Big Bend 

 of the Columbia, for instance, where the annual rainfall is but half 

 as great as ours, good crops of fruit, peas, potatoes, beets, carrots 

 and onions are grown every season, and large yields of wheat and 

 barley are secured without fail once in two years. This result is at- 

 tained by saving the snow-water of the winter following the crop 

 year until that of another winter is added to it, when the land is 

 ready for another heavy yield. "Of course," every farmer will say, 

 "that is important and in the highest degree desirable, but how can 

 it be done?" The question is not a very difficult one, and the 

 farmers whom it confronted were not long in reaching a conclusion. 

 They pretty effectually checked direct evaporation by keeping the 

 surface covered to the depth of two or three inches with a light, open 

 dust mulch, and indirect evaporation by allowing nothing to grow 

 on the soil during the off years. 



The movement of water from the moist depths of the earth is 

 constant until some obstruction is met. A stratum of coarse gravel 

 and pebWe stones offers such obstruction, the pores not being suffi- 

 ciently fine to invite capillarity to do its work. A soil, air-dried or 

 nearly so, by sun, wind and the absorptive power of vegetation, per- 

 mits only a slow and feeble movement of water through it. When, 

 to such a condition as has just been described is added an exceed- 

 ingly light, dry and open textured dust blanket, the bar to the further 

 upward movement of capillary water is well-nigh complete. The 

 reason for this will be readily seen when it is understood that 

 capillary attraction is but a form of adhesion and can take place only 

 when the liquid has a stronger power of adhesion to the substance 



