The Raisin Industry / A practical treatise on the raisin grapes, their history, culture and curing

by Gustavus A. Eisen

Health and Longevity of Irrigated Vines.

—As regards the health of the vines, the old idea in this country that vines would suffer from irrigation is decidedly erroneous. The vines of Denia in Spain have been irrigated for eighty years or more, and are to-day the healthiest vines in Spain. Similarly, the Fresno vines, where the water level, as in Denia, is only from five to ten feet below the surface, show no signs of decay, while many of the raisin-vines in other parts of the State, especially where planted on the hillsides, show diseases which baffle the cultivator. I do not, of course, mean to say that irrigated raisin-vines are entirely free from diseases, but only that, so far, the healthiest and strongest raisin-vines of the world are those which are irrigated, and which have always been irrigated. Of course in this respect the Muscat grapes, as well as the currant vines, differ materially from certain wine grapes, which as a rule have originated on drier soils, and which, if grown with irrigation, deteriorate and yield inferior fruit. The raisin-vines require much moisture, and, if this is not supplied in one way or another, they will suffer and prove unprofitable. The same is observed in soils which rapidly lose their moisture. In such soils the Muscat is not at home, and its health and vigor is seriously impaired.

The Bearing Quality of Irrigated Vines.

—In regard to the bearing quality of the raisin grapes under irrigation, we know with certainty that the irrigated raisin-vines yield by far the most. In Valencia and Denia, the vines yield from five to ten tons to the acre, and so do those of Riverside and Fresno, while the El Cajon unirrigated vines yield only from one to two tons per acre. If the latter place would irrigate judiciously, its Muscat vines would no doubt bear as well as those of any other locality. I am led to this belief from what I have seen of irrigated grapes elsewhere in San Diego county, which were fully as well loaded as the heaviest vines in San Bernardino county or Fresno.

Quality of Irrigated Grapes.

—That the quality of the irrigated raisin grape is increased by judicious irrigation is readily seen in all irrigated districts, where those vines which receive their proper share of water produce the largest bunches and berries. But it is also evident that too much water will cause a deficiency of sugar in the grapes, as well as a lack of flavor, by which the irrigated grapes can always be distinguished from those grown with natural moisture. Grapes too freely irrigated are not alone wanting in sugar, but also in color. Such grapes remain green to the end of the season, and never assume that amber color so valued in grapes, and which always indicates beforehand what raisins they will produce when properly dried. In our interior valleys, where the sun and the wind sometimes produce sunscald of the berries, which again causes them to fall off or dry up long before they are properly ripe, this defect is much more frequent on vines which suffer from want of water than on those which have had enough. When the soil is not subirrigated, it is therefore advisable to irrigate the vines at the end of June, just before the hottest part of the summer arrives. Similarly, irrigation will help to swell out the berries if applied just before they commence to ripen.

In conclusion we might with truth say that the raisin grapes may in many localities be grown without irrigation, but that in California, in Greece and in Spain, the largest and most prosperous districts are those where the raisin-vines are liberally irrigated. The Muscat grape seems especially to love water, and, in the real raisin districts, the healthiest vineyards are those that are best irrigated. The berries and bunches are also increased in size, but not in flavor and aroma, by irrigation. In places where the raisin grapes will not bear without irrigation, the latter, of course, is a necessity. There are always naturally subirrigated parts, in every county or district, where artificial irrigation is not required. But these parts are generally confined to river bottoms or to natural sinks, which, so far, have played no important part in the raisin industry. Considered from a practical standpoint, irrigation of the raisin-vines is necessary in California, and, should it from some reason or other be made impossible, the raisin industry would not prove profitable or even possible, except in a few very limited localities.

Much has been written in regard to the supposed unhealthiness of the irrigated vineyards. The malaria prevalent in some vineyards is no doubt caused by irrigation; but it has been amply proved in Fresno and elsewhere that if the grower would know from the beginning how to so prepare his land that there would be no stagnant pools, no waste water, and no swampy grounds, the so much talked of malaria would be as rare in the irrigated vineyards as anywhere else. It is not the irrigation that causes malaria, but the waste of the water, the carelessness of the irrigator and the faultiness of the badly constructed irrigation works. After the vineyard has been irrigated a few years, the malaria leaves it entirely. This is the experience in Fresno where the vineyards, after years of irrigation, have become perfectly healthy.

Various Methods of Irrigation.

—There are several methods of irrigation now practiced in the irrigated vineyard districts. We may irrigate by flooding the land or by leading the water in furrows between the vines. Both ways, but especially the former, may, if continued long enough, cause subirrigation, the most desirable state of irrigation. The choice of methods of irrigating does not always lie with ourselves, but depends upon the quantity of water at our command, the lay of the land, etc. Sometimes one method will in course of time give room to another, and again, after the lapse of a few years, continued irrigation may not be necessary or desirable.