—It is by many considered that irrigation helps to fertilize the soil. The spring and flood water contain great quantities of mud and humus, which when spread over the land will greatly increase its fertility. Even ordinary river water contains salts and other ingredients, which will fertilize the soil to no small degree. Another cause of the increased fertility of subirrigated soils is that the water which constantly evaporates carries with it salts, etc., from the lower strata up towards the surface, and makes them accessible to the roots of the vines. But, on the other hand, if the water or the soils contain alkalies or other destructive substances, these also are deposited on the surface to the great detriment of the vines, and often to such an extent that the vines will die or become sickly. Too abundant flooding may also leach out of the soil its soluble salts, and carry them deeper down in the ground. But if this soil after a while fills up with water and becomes subirrigated, the evaporation of water from the surface will gradually carry these salts back to the surface, when they will increase the fertility of the soil. Where drainage is very perfect, constant irrigation will gradually rob the soil of many of its soluble salts, and carry them to places where they will forever be out of the reach of the vines. To ascertain these facts and conditions, every vineyardist should have the soil analyzed about every five years, and too great care cannot be taken to keep the soil of proper strength.
Another influence of irrigation on the soil may also be mentioned here. Some of the soils in the irrigated districts which were formerly very hard and difficult to work have in course of time changed and become mellow. The water has undoubtedly caused a chemical and mechanical decomposition of the components of the soil, which has caused it to continually improve. Even certain kinds of hardpan have been known to dissolve when irrigated, and to change into useful and mellow soil, in which the vines can find nutriment. Such hardpans are those which are generally found in very dark red soils; those in lighter soils are not so readily dissolved.
THE RAISIN GRAPES.
Introductory Notes.
—The raisin grapes might be divided into two classes,—proper and genuine, such as Muscats, Sultanas and Currants, and irregular or inferior raisin grapes, such as Malagas and Feher Szagos. Now-a-days almost any kind of grapes are dried and sometimes called raisins, but the proper name for them should be dried grapes. With these we need not here busy ourselves, as with a few exceptions they are of little value, and cannot be compared with the regular raisin grapes, either as regards quality, demand or price.
Muscatel or Gordo Blanco.
—This variety is the best type of the raisin grape of Malaga. Its growth is low and spreading, with no upright branches in the center. Its bunches are heavy, and, when perfect, close and shouldered. Its berries are round and large, the greatest circumference being at the center. A crease is often found at the apex of the berry. The color is green, or, when fully ripe, amber green or yellow. As compared with the Muscat of Alexandria, this variety is distinguished, when perfect, by its low, depressed growth, without any upright branches in the center of the vine; by a closer bunch; by rounder berries, and by a thicker and firmer bloom. The berries set better than those of the Muscat of Alexandria, although both varieties suffer from the early stages of oidium or colure. The Gordo Blanco is the choice raisin grape for the San Joaquin valley, and for the interior generally. It is the raisin grape of Malaga in Spain, where it is probable the variety originated. Importations of this variety have been made to California at various times by A. Haraszthy in 1861, and by W. S. Chapman in 1876.
Muscat of Alexandria.
—The growth of this variety is upright in the center. Its clusters, even when perfect, are never close. Its berries are oblong and tapering, the largest circumference being near the apex. The color when fully ripe is amber green or yellowish green. The leaves of both varieties of Muscats are five-pointed, light green, lighter below, and do not differ materially from each other. Both Muscats are remarkable for their second and third growths, and for the large second crop on the laterals.