218 STORRS AGRICULTURAL EXPERIMENT STATION. 
illustrated in greenhouse culture, where nearly all of the soil 
receives a thorough wetting once in two or three days. Here, 
also, heat and light are toa great extent under control. In field 
culture heat and light cannot be controlled, but food and water 
may. The subject of fertilizers and manures and their influ- 
ence on the growth of farm crops has been carefully investi- 
gated during the past twenty-five years. Fertilizers, however, 
are of little use without an abundance of water to render them 
available for the plant. One of the most serious drawbacks in 
conducting field experiments with fertilizers is the fact that the 
water supply cannot readily be regulated. It frequently hap- 
pens that in seasons of drouth the value of such field experi- 
ments is almost destroyed; or if deductions are drawn from 
them without regard to the moisture conditions of the particu- 
lar season, such deductions are apt to be very misleading. 
It is important to study all possible means for conserving the 
water in the soil by preventing its escape, and thus retaining it 
where it will be available for the plant when most needed. 
Much can be done to this end by the addition of humus, either 
in the form of stable manure, or other decaying vegetable or 
animal matter, or by placing some suitable mulch on the sur- 
face of the ground, or by forming a mulch from the surface 
layers of the soil by frequent cultivation; but with all these 
helps crops will at times suffer for want of the necessary water 
to keep up a vigorous growth, unless an artificial supply is 
provided. 
A large proportion of the weight of most plants is water. 
This is familiar to all, in the fact so readily observed, that plants 
and fruits lose weight rapidly in drying. In every 100 pounds © ? 
of freshly cut grass there are from seventy to eighty pounds of 
water; while clovers frequently contain over eighty per cent. 
Nearly all of our common fruits, such as strawberries, rasp- 
berries, pears, and peaches, contain from eighty to ninety-two 
per cent. of water. The importance of this to the farmer is 
seen in the fact that when he sells such crops off the farm he is 
mainly disposing of water and a small amount of mineral salts. 
The water held in the substance of the plant, however, 
represents only a small part of that needed in its growth; a 
large amount is transpired through the foliage during the 
period of the plant’s development. 
