No. 6. DEPAKTiMENT OF AGRICULTURE. 34J 



taices froui Llic soil iiiusL be in soluliou, and, oi' uecessitx', in very 

 diJiUe solution. Large quantities of Abater are required to act as a 

 solvent and carrier of food. It is really a breathing process. The 

 root-hairs take up the water, ladened with the plant food elements, 

 Iroin the soil. It is carried upward into the plant, the dissolved 

 material being absorbed and the excess of water being evaporated 

 from the leaves. 



Experiments have been conducted which show that for every ton 

 of dry matter of corn produced 310 tons of water are required; for 

 every ton of dry matter of oats 522 tons; and for every ton of dry 

 matter of potatoes 122 tons of water are consumed. In addition 

 to the actual needs of the plant, the presence of water is necessary 

 to accomplish those changes in the soil which render plant food 

 available and which bring about the improvement of the physical 

 })roperties of the soil. 



The source of supply of all this water is, of course, the rainfall. 

 The average rainfall for several years past has been in the neigh- 

 borhood of 42 inches. An inch of rainfall means that if the water 

 falling during a certain time wen- evenly and uniformly distributed 

 over the surface of the ground in such a way that if it could not 

 escape it would collect to a dept of one inch. To state it in a 

 more concise way, an inch of rainfall is equivalent to 113 tons of 

 water to the acre, so that in \hr course of a year every acre receives 

 about 1,500 tons of water. This would be suhicient to supply 

 any crop with an abundance of water were it all available. Much 

 of this watei-, however, never sinks into the soil, but runs off the 

 surface and is not only lost, so far as its use by the plant is con- 

 cerned, in many cases carries with it much more soluble plant food. 

 The ditficulty arises from the uneven distribution of the rainfall 

 and not from its limited amounl. .Vs it is the water which falls 

 during the late fall and early spring and sinks in to the ground, 

 coming to the surface again during a dry season, upon which the 

 plants must chiefly rely for its drink, it is apparent that the first 

 problem to solve is one involving the securing of that soil condi- 

 tion wjiich will permit of a innxiniuin absorption of water. Then 

 if subseiiucnt unnecessary loss of this water by evaporation can be 

 jireventcd, we will be a])[)ro;!cliiug a solution of the difficulty. 



Those years in wJiicli naluial moisture conditions are most favor- 

 able give usually the most iibundant harvest. Now if in an unfavor- 

 able season these conditions can be controlled within certain limits 

 through artiticial means, the individual exhibiting the greatest 

 skill in this direction will reap the greatest reward. 



Before proceeding to a discussion of a few of the factors which 

 influence the retentiveness of soils for moisture, it may be desirable 

 to refer, brieflv to the wa\' in which water is found in the soil. 



