16 BOAED OF AGRICULTURE. 



depends largely on the kind of crop, nnd the condition of 

 the surrounding air. On a hot, dry day, evaporation is 

 often excessive, and if the supply of water is not abundant 

 the plants Avilt. 



Sir J. B. Lawes found that common plants exhaled, during 

 the five months of their growth, more than two hundred 

 times their dry weight of water. This water is all drawn 

 from the soil. Dr. J. H. Gilbert, in a pamphlet on " Rain- 

 fall, Evaporation and Percolation," says, that " the amount 

 of water given off by plants during growth might be 

 roughly estimated at a depth of three inches of rain for 

 every ton of dry substance grown." According to this 

 estimate, a crop of three tons of dry fodder (which is a 

 large crop) on an acre, would require nine inches of rain- 

 fall, provided it was all utilized by the crop. This is a 

 large amount of water, yet it is but twenty per cent, of 

 our averajre rainfall. In Southern California a rainfall of ten 

 inches has secured abundant crops, and fifteen inches is con- 

 sidered sufficient, if evenly distributed through the wet 

 season. It is quite evident that our rainfall, provided it 

 could all be utilized, would be very much more, even in dry 

 years, than the amount required by our crops. 



If, then, our annual rainfall is more than equal to the 

 demands of our crops, how is it that they suffer so severely 

 from droughts during portions of almost every season ? It is 

 because the rainfall is not evenly distributed through the 

 season. We get too much at times, and then for weeks, or 

 even months, we receive only a scanty allowance. This is 

 particularly true of the summer, when the crops are grow- 

 ing and need the most ; while at such times the evaporation 

 is excessive, both from the leaves of vegetation and the soil. 

 Summer droughts are the common accompaniment of our 

 New Eno-land summers. 



The Secretary of this Board, in his last annual report, 

 truly says that: "The thirty volumes of our reports are, 

 with several exceptions, a record of drought. It is almost 

 as certain to come as the summer. The Massachusetts 

 farmer must prepare to meet it, and so plan his operations 

 as even to turn it to his account." 



But we have another difficulty here with which to con- 



