464 MINNESOTA STATE HORTICULTURAL SOCIETY. 



wind here is but three-fifths as great as in New England, whence 

 the charge against Minnesota generally comes. The one thing 

 which injures us more than all other physical factors combined is 

 the scant rainfall of August and September. This year there has 

 been no reason to grumble, but the usual condition during the latter 

 part of the growing season is that of dryness. It seldom makes 

 itself felt early enough to seriously damage the small cereals and 

 other early ripening crops, but flax, millet, all roots and also fall 

 pasturage often suffer greatly from drought. Corn, though strictly 

 a cereal, ripens late but has such power to resist heat and dryness 

 that a general failure is unknown. Occasionally it happens that 

 the whole summer is dry, and all crops are more or less injured. 



This brings us to the all-important question, can the tiller of the 

 soil do anything to relieve the situation when unkind fate refuses the 

 earlier and the later rains? In cultivated land much may be done 

 by conserving the moisture already stored up in the ground and 

 giving it to the crops for their exclusive use. There will always 

 be two enemies to fight : first, leaching, which will be mentioned 

 later; second, evaporation, which operates in two different ways, 

 one direct from the surface of the ground and the other 

 indirect, through the leaves of the weeds that everywhere infest 

 the cultivated fields. Fortunately both forms can be fought at the 

 same time and both subdued by the self same weapon, the cultivator. 

 It provides the dust mulch to avoid direct evaporation, and by de- 

 stroying the weeds stops the exhalations from their leaves. 



Direct evaporation is simply the action of the thirsty air as it 

 wanders over the surface, licking up the moisture which capillary 

 attraction has brought up from the lower layers of soil and placed 

 within its reach. This attraction is the same as that which causes 

 water to rise in fine glass tubes above the level of that on the out- 

 side. The saturation of a lump of sugar by inserting one corner in 

 a cup of tea is a familiar illustration of the work that is constantly 

 going on underground. When the interstices of the underlying 

 strata are of the right degree of fineness, when the soil is sufficiently 

 firm and compact and of uniform texture, capillarity goes steadily on, 

 and an almost incredible amount of moisture is daily lifted from 

 beneath the ground to the surface. 



Evaporation from growing weeds is often very much greater 

 than that which takes place directly from the surface. Every one 

 is familiar with the fact that trees afford decided protection from 

 light showers and from the first part of a heavy rainfall. In the 

 middle and far west about one-fifth of the rain which falls where 

 the ground is covered with trees and other vegetation is evaporated 



