164 fertilizers in Irrigation Water. 
ahead of the grain-seed drill and to distribute and drill in the 
fertilizer as deep as feasible to do without injuring the roots. 
Manures with Irrigation Water—Distribution of fertilizers 
by using the flow of irrigation water is described by A. S. Chap- 
man, as follows :— 
We shovel sheep manure into the irrigating ditches, allowing each tree 
to receive about twenty-five pounds at each separate irrigation. Our basins 
cover the entire surface of the ground. We make no effort to choke such 
weeds as clover, alfilerilla, and the like; but the irrigator with his hoe 
destroys the obnoxious nightshade, hoarhound, and nettle. 
In the fall of the year we follow with copious liming—about three bar- 
rels of unslacked lime to the acre—applied in the following manner at the 
head of our irrigating ditch: We plant a box about three feet wide, six feet 
long, two feet deep, and six inches under the surface of the running water. 
In it we place a barrel of the lime. It slacks and swells to twice its orig- 
inal bulk. A man stands on this with his hoe and sees that the water car- 
ries it off evenly. With an irrigating head such as we use, a man will run 
into the ditch four barrels a day, or about three barrels to the acre. We 
have a considerable fall, and the water runs very rapidly; but it takes up 
all the lime, and the water runs white, like milk. ; 
We now leave the orange orchard till spring, when we plow under 
weeds, manure and lime. We thus aim to supply our soil with nitrate of 
lime, potash, and magnesia. Carbonic acid gas is absorbed by the water 
and attacks the inert plant food in the soil; hard-pan is prevented both by 
the mechanical effects of the vegetable matter and the lime. 
The basin method of irrigation, to which allusion is made, 
will be more fully described in the following chapter. 
FERTILIZING MATTERS IN IRRIGATION WATER. 
Water used for irrigation may carry in solution injurious 
substances, as, for example, alkali, as will be noted in the follow- 
ing chapter; or it may carry very valuable fertilizing properties. 
These facts can only be determined by analysis. Professor Hil- 
gard has found that the water of one creek in Alameda County 
carries to the land it irrigates about half a grain of potash in each 
gallon, which means that if twelve inches of such water were 
used on the ground during the season, each acre would receive 
therefrom about twenty pounds of fully available potash. At 
Riverside a crop of oranges requires about forty-two pounds of 
potash per acre, of which the amount of irrigation water gen- 
erally used contains thirty-five pounds besides other matters re- 
quired by plants. These things have a definite cash value in the 
market; and this value the irrigator gets as a free gift in addition 
to the water. Even in the case of the Nile, the sediment is only 
part of the sum of fertility conveyed by the river. 
GREEN MANURING. 
Green manuring consists in plowing under a growth of 
weeds or a sown crop to secure by its decay a contribution of 
