Timely Hints for Farmers. 1U 



be resoited to. Thorough cultivation is one means of compensat- 

 ing fcr a shortage of irrigating water. Orchards and all crops 

 planted in rows may be made more productive during dry weath- 

 er by keeping the surface of the soil well pulverized. 



The effects of cultivation are three-fold— (i) the aeration of 

 the soil, (2) the conservation of moisture, and (3) the destruction 

 of weeds. 



The aeration of the soil is very important. That the neces- 

 sary biological and chemical processes may proceed properly in 

 the soil, a constant supply of oxygen is essential. If these pro- 

 cesses cannot continue, a crop may starve, though there be an 

 abundance of riw material in the soil. After rains and more es- 

 pecially after irrigation most soils form a crust over the surface, 

 or "bake" to some depth, and thus free access of air is prevented. 

 Cultivation breaks up the surface and promotes the aeration of 

 the underlying soil. 



The conservation of moisture by cultivation is based on well- 

 established principles. During a rainstorm or during irrigation, 

 the water received by the soil moves downward. As scon as the 

 supply from above ceases and the free water settles away, by cap- 

 pillary action the movement of the moisture in the soil sets in in 

 the opposite direction, moving upward as well as downward. As 

 the moisture reaches the surface, it passes off as vapor. Only by 

 preventing the water reaching the surface can this evaporation be 

 checked. The capillary action by which the water reaches the 

 point where it evaporates can go on only in a closely packed soil 

 furnishing the innumerable, minute, irregular tubes through which 

 the water rises. To break up these tubes checks this upward 

 movement. Cultivation not only breaks up the capillary tubes of 

 the surface, but forms over the surface a mulch that prevents 

 rapid evaporation. The moisture will then rise to the mulch, but 

 cannot piss beyond it by capillary action, and evaporation thus 

 proceeds much more slowly than if the moisture were permitted to 

 follow the capillary tubes to the surface. 



Samples of soil taken recently in an orchard illustrate the 

 foregoing. The orchard in question had been irrigated last on 

 March 5. Most of it had been thoroughly cultivated; but a por- 

 tion had been left uncultivated, and had become overgrown with 



