Scientific Agriculture. 



36 



[Jan. 1908. 



water farther down, so that such a rain, which would still be a heavy one, would 

 moisten the soil probably eight or ten inches. Since the soil is seldom so dry as to 

 be at the wilting point, but generally contains from 15 to 20 per cent, of water and 

 sometimes more, a rain of about oue inch is often sufficient to cause percolation. 

 A saturated loam contains about 30 to 35 per cent, water by weight. 



The season of 1906 was a very wet one during the growing time, and the 

 same test resulted as follows : — 



Table showing Rainfall and Depth of Water used by Crops 

 during a Wet Season. 



Crop. 



Depth of rain 



while crop 

 was growing. 



Depth lost by 

 drainage. 



Depth of water 

 added. 



Net depth of 

 water used by 

 crops. 



Total depth 



compared 

 with rainfall. 



Wheat- 



12-62 



1-00 



5-00 



17-32 



1'38 



Peas ... 



12-62 



1-00 



6-00 



18-32 



1-45 



Barley... 



12 '62 



1-00 



6-50 



18-82 



1-49 



Oats ... 



12-62 



TOO 



6-25 



18-47 



1-47 



Thus we see that during a wet season the crops do not use as much water 

 as during a dry one, only about 18 or 19 inches in 1906, as compared with 23 or 24 

 inches in 1905, although the supply was much more abundant. Still they usep 

 about one-half more than the rainfall ; but any soil, whatever its condition, retains 

 enough of the spring and winter precipitation to supply this deficiency. The table 

 also shows that part of the rain was carried away in drainage. In actual field con- 

 ditions the amount to be thus removed woald be much greater. Moreover, it is a 

 matter of common observation that excessive water standing in the soil for 

 48 hours or more is very injurious to plant life. Hence, during a wet season it is 

 our chief concern to remove the surplus water before its presence becomes dangerous 

 to the crop. 



Now it is a curious coincidence, or shall I say a provision of nature, that in 

 most soils the conditions which, in a dry season, make for the retention of great 

 stores of the winter and spring precipitation, and the subsequent conservation 

 thereof, are the very conditions that in a wet season rid the soil most quickly of the 

 surplus water. It behoves us, then, to inquire what these conditions are. First 

 and foremost a proper soil texture, a grandular condition not too fine nor too coarse, 

 neither too compact nor too loose. Let me illustrate this by a simple experiment. 

 Here are two brass tubes with sieve bottoms. Equal weights of loam were placed 

 in them. In tube No. I the soil was packed to field conditions ; in tube No. 2 it was 

 left as loose and open as possible. Water was poured carefully into each and 

 allowed to soak through. When both soils were just filled with water, the loose 

 one contained 34 per cent, more than the compact. In soil six inches deep this is 

 equivalent to one inch of rain, i.e., if a loam is loosened up for a depth of six inches 

 it will absorb one inch more than the compact soil before any of the water is lost 

 by surface run off. The tubes were then let drain, and when all drainage had 

 ceased it was found that the loose had retained 28 per cent, more water than the 

 compact, which amounts to four-fifths of an inch in six inches of soil. This is equiva- 

 lent to a very heavy rain. A further test was made with these two samples. We 

 measured the rate of drainage, and it was found that the loose soil allowed water 

 to pass through it more than twice as fast as the compact did. 



This illustration demonstrates one of the chief objects in fall-plowing, viz., 

 the absorption and retention of water ; it also teaches that deep ploughing will 

 achieve this object better than shallow plowing, and further that subsoiling may 



