Scene in a Fresno Raisin Vineyard: Raisin Trays Exposed for Drying.
Chile.
—The Huasco grape grows in the valley of Huasco, on the coast of Chile, in a soil that is very light and red, containing a great quantity of sand. While very light in weight, this soil is said to be very rich in plant food, and yields good crops.
Fresno.
—The Fresno soils are of several kinds, but the three principal varieties are red or chocolate-colored loam, white or gray ashy soil, and a light, very sandy, loam. To this may be added the deeper gray bottom soils or alluvial deposits of the Kings river. Each one of these varieties have different grades more or less suitable to the Muscatel grape. The best grades of each are equally valuable, while again the poorer grades are not to be recommended. The deep chocolate-colored loam is by many preferred, and the largest and most successful raisin vineyards are now located on this soil. But even in the best districts the soil varies to such an extent, that while one twenty-acre field will yield 250 boxes of raisins to the acre, the adjoining field, with only a slight change in the soil, will yield only seventy-five boxes to the acre. The best grades of the white ashy soil are also very good, and almost identical with the gray bottom-land deposits of Kings river. The light sandy soil should be avoided for Muscat grapes, but may do for Malaga and Sultanas, especially if judiciously fertilized.
Other Soils in San Joaquin Valley.
—In Merced the best soil is heavy chocolate-colored loam, in places redder, in others darker, almost blackish. It is generally mixed with some gravel. As a rule, all the red soil in the San Joaquin valley is of the same characteristics, and well suited to the Muscat grape, provided the ground is sufficiently level. In Tulare county the proper soil for the Muscat is found to be the bottom lands of Kings and Kaweah rivers, as well as the deposits of the smaller creeks. This variety of gray alluvial loam is exceedingly fertile, and there is none superior for the Muscat grape. But an admixture of alkali often spoils soils which otherwise would be considered the very best. A similar soil is found in Kern county, especially near Kern Lake, and which must be rated among the best in the State, its color being a deep bluish gray. The vineyards of Yolo and Solano counties are located on a very similar soil, rich in humus, lime and phosphates, but more yellowish or pale chocolate colored.
Orange County.
—A similar rich alluvial deposit is found in Orange county in the fertile district known as Santa Ana valley. The soil around Anaheim, Santa Ana, Orange and Tustin consists of a more or less dark alluvial loam of unsurpassed fertility, and especially adapted to the Muscat grape. It varies as to the percentage of sand and gravel. The sandiest soil in this district, while less rich, brings the earliest grapes, which come to perfect ripeness several weeks before those grown on the heavier soils, but the latter produce the best raisins.
Redlands and Riverside.
—The Redlands soil of the mesa lands is reddish, rather darker than the same quality of soil in Riverside and Fresno. It is mixed with sand and gravel, and partakes strongly of the nature of the red or chocolate-colored loams of the State. The Lugonia bottom soil consists of a very sandy loam, on which the Muscat grape has proved a failure. The best Riverside soil is red or chocolate-colored sandy loam, so often spoken of. Towards Rincon we find alluvial bottom soils producing grapes of superb quality and size. The soil of the San Bernardino district resemble the red Fresno soils, while the white ashy soil is not found there.
El Cajon.
—The El Cajon valley soils are of three or more kinds: Rich red clay mixed with gravel, with the color changing from lighter chocolate to deeper reddish. This is a very desirable soil,—a steel gray or slate gray adobe with much gravel of a coarse nature; a black adobe with some gravel; an alluvial sandy loam consisting of decomposed granite mixed with much vegetable matter and humus. The El Cajon soils, while sandy and gravelly, produce exceedingly sweet and highly flavored grapes but comparatively small crops.
Subsoils.
—The subsoil in a raisin vineyard is of great importance. Properly irrigated soils, if they are sufficiently rich, need not necessarily be very deep, as the raisin grapes, especially the Muscat, seldom extend deeper than eight feet below the surface. Even from four to five feet of rich soil may be considered as enough in irrigated vineyards, where the water is abundant. In poorer soils, or in districts with less irrigation, the roots of the vines penetrate much deeper, and the importance of the subsoil in such cases is apparent. Any rich subsoil will serve our purpose. It is always best to thoroughly investigate the subsoil before the vineyard is planted, and in doing this the following points must be considered: The subsoil should be as rich as possible, and there should, in no instance, be less than four feet of rich top soil. Very sandy soil or pure sand is not a proper subsoil for raisin grapes. Such soil will cause the top soil to dry too quickly after each irrigation, and will cause the top soil to leach out, while it besides gives no nourishment to the vines. Hardpan is not desirable, not even admissible, except in places that are or will become subirrigated. Alkali or salty subsoils will soon spoil the quality of even the best top soil. This especially is the case in irrigated districts, where the salts of the subsoil are carried to the top by the rising waters or by the continued irrigation. Hardpan which readily dissolves when wet is not injurious.
Hardpan Soils.
—While I have alluded to them already, a few more remarks on these soils are here in place. The hardpan consists of a stratum of hard soil or hard rocky substance below the top soil. The depth at which the hardpan is found varies. In places where it is situated eight or ten feet below the top surface it does but very little harm, and may even prove beneficial in localities where water for irrigation is scarce, as it checks too rapid drainage. If the hardpan is situated closer to the top soil, it may seriously interfere with the vines, and if too close, or say within two or three feet from the top, it makes such soils entirely unfit for raisin grapes. If situated somewhat lower down, say from four to six feet, the hardpan does no great harm in subirrigated districts, while, in places where irrigation is not used, it leaves the top soil too shallow and too dry. But allowance must always be made as to the nature of the hardpan. Some varieties of hardpan are so hard that they can best be compared to regular stratified rocks, impenetrable to the roots of the vines, and impervious to water. Other hardpans again are softer, and allow the vine roots to penetrate more or less readily, while some again are so soft that they dissolve in water and make good soil for the vines. If the hardpan is very shallow, it may pay to blast holes through it, in order to allow the roots of the vines to penetrate to lower soils. But if the hardpan is thick and hard, and if there is no immediate prospect of subirrigation, it is better to use such land for some other purpose than for raisin-vines, which will only pay properly if grown under the most favorable circumstances, and on the best and deepest soils.
As to the nature of the hardpan, a few remarks may prove of interest. The hardpan can best be compared to a stalactite formation similar to those found in various caves. It has been formed very much in the same way as they were. In caves the rainwater, that seeps down from the top surface, dissolves various substances, especially carbonates (and silicates even) which again are deposited on the underside of the cave roof. This precipitation of hard material is caused both by evaporation of the water, as well as by attraction and adhesion. Such redeposition of dissolved minerals is seen for instance if solutions of salt in water are passed through tasteless and clean sand. The water will come through sweet and tasteless, the salt having adhered to the surface of the sand grains. Similarly, if a hole is dug near the seashore in the sand, the salt water will seep through, and form a well of more or less tasteless drinking water. In the formation of hardpan, this is exactly what has taken place. The rainwater has dissolved certain elements, such as carbonates of lime, or carbonates of sodium and various other salts, and in its way through the lower strata of the soil these dissolved elements have again been taken up by the sand and cemented it together. Thus it is explained why hardpan upon examination is so often found to resemble sand or sandstone: the lower sandy strata of the soil have been especially effective in causing the lime in the water to adhere to the numerous surfaces of every individual grain of sand. In hog-wallow districts the hardpan is found principally between the individual hog-wallows, but rarely in or under them. The rainwater has here carried the minerals in the soil to the deeper places between the hog-wallows, in which it has accumulated to a greater extent than anywhere else, and thus formed a heavier hardpan. In flooding the hog-wallows, the top of every hog-wallow is seen to settle and fall in, there being no hardpan below it, if the sides of the hog-wallow are steep. Where the hardpan consists principally of lime compounds, its chemical composition is not detrimental to the vines. But where the hardpan is cemented by alkalies more or less soluble in water, these deleterious substances will dissolve and rise to the surface to the great detriment or even to the total destruction of the vineyard.
Comparative Value of Soils.
—The river bottom soils, or soils formed by the deposit of creeks, are with few exceptions rich and deep, and contain in abundance all the elements necessary to produce a superior Muscat grape. Such soils are, however, often injured by subsoils containing mineral deposits, which will injure the vines, or by hardpans, which will cause the soil to dry out. Poor soils will not prove profitable, and rather than plant vines on such soils it would be better to plant no vines at all. The rich soils are not only the heaviest producers, but the vines grown on them are stronger and healthier and in every way better able to resist the attacks of insects and fungi and the ravages of other inexplicable diseases. But regardless of these advantages the various soils leave their effects on the grapes, some of them producing sweet and very keeping raisins, while others cause large berries and bunches, which bring the highest market price. Thus the lighter and drier soils produce richer flavored and sweeter raisins than the wet and rich soils, which again produce the largest and handsomest grapes. On the latter soils the raisins when cured will be found to be dark and covered with a heavy bloom, while the raisins from the sandier or gravelly soils are lighter in color and with less pronounced bloom. The keeping quality of the raisins from gravelly soils is well known. In California the keeping quality of the raisins is seldom inquired into, as our raisins keep remarkably well and are in this respect superior to those grown in Spain. This may be from the effect of our drier climate more than from any certain quality in our soils.
As a rule it may be said that poor soil causes the raisins to mature earlier than the rich, heavy loams, and on this account the latter are to be greatly preferred, as the earliest raisins in any district are never as good as the bulk of the crop, and are in demand rather as a curiosity, and for the purpose of supplying an early market, than through any superior qualities. In some districts there is such a great difference in the time of ripening upon the various soils that the grapes grown on the earliest soils are used only as table grapes fresh. In planting a raisin vineyard, the future profits depend upon the choice of land, and it is far better to pay a high price for the best land than to take the inferior land as a gift. Few of those who now enter upon raisin culture take the proper care in selecting the land, neither do they sufficiently, if at all, realize the advantages of the rich soil, nor the disadvantages of the poor land.
Alkali Soils.
—While nothing but first-class land is to be recommended for raisin vineyards, and alkali lands are of all soils those least suitable for our purpose, still a consideration of these lands will interest many raisin-grape growers. The best lands for raisin purposes in California are often contiguous to alkali lands, or to land containing more or less traces of alkali. A vineyard on the best soil contains often spots charged with alkali, and it may be inconvenient for the grower to allow these spots to lie idle, and he would prefer to fill them up with vines. The first work must then be to get rid of the alkali or reduce it to such an extent that it will not prove injurious. The general alkali lands are classed in three kinds, according to the quality of the alkali.
1st. Alkali salts, such as carbonates and borates. These are greatly detrimental to the vines, and no vines could be expected to do well in such soils, as even the smallest percentage of this alkali is injurious or even ruinous to the crop. In clayey soils these alkalies cause the clay to harden in such a way that no good tilth can be obtained. The land may be plowed ever so much, it will only turn up in chunks and never become properly pulverized. These true alkali salts consist principally of carbonate of sodium (sal-soda) or of carbonate of potassium (saleratus). Remedies: Gypsum, land-plaster or leaching with water.
2d. A second class of alkalies are the sulphates and chlorides, all soluble in water. Such salts are: Magnesium chloride (bittern), magnesium sulphate (Epsom salt), calcium chloride, etc. These salts, when not present in too large quantities, are easily counteracted by lime.
3d. A third class of alkalies is composed of neutral salts, such as chloride of sodium (common salt), sulphate of sodium (Glauber salt), sulphate of potassium, all soluble in water, but not convertible into less injurious substances by lime or gypsum. These salts do not bake the soil, but rather contribute towards keeping it loose and mellow.
The remedies which are practical and not too expensive may be divided into several classes, which, if used in combination, may prove effective, while each one of them used separately would fail.
1st. Leaching with water. All soluble salts may be leached with water. The alkali land should be checked and so ditched that the water from each check can be drained into a waste ditch. But, besides these waste ditches, drain ditches should be made for the purpose of draining off the water, say to a depth of four feet below the surface. The modus operandi consists in first flooding the soil, and while the check is yet full the floodgates are opened and the water drawn off into the waste ditch, when the water will carry off the salts which have been dissolved in it. A second or third flooding should be allowed to settle in the soil and be drained off below into the drain ditches. The drawback to common leaching is that under certain circumstances the water may deposit its alkali in lower strata, especially if they are sandy, and there form hardpan or alkali accumulations. A much better method is under-drainage by means of pipes or gravel drains constructed all through the tract at certain regular distances. This under-drainage, if properly constructed under conditions favorable for its perfect working, is by far the best method of freeing alkali soils from their superfluous salts. To what extent this system is practical depends upon circumstances. To reclaim large districts by this method may not prove economical as long as good land is plentiful and cheap, but where smaller alkali tracts are surrounded by soil, and where it is of importance to get a uniform plantation, under-drainage by pipes or common drains is both the surest and most practical solution of the alkali problem. Under-drainage is strongly recommended by Prof. E. W. Hilgard, who has repeatedly pointed out its value, and who has called the author’s special attention to this as yet little understood remedy.
2d. Deep and constant plowing. Deep and frequent plowing acts in various ways. By being mixed with a larger quantity of soil, the alkali is diluted sufficiently to not cause any serious injury to the crops, the damage generally being done near the surface. Constant plowing also prevents evaporation, which carries the alkali to the surface and deposits it there. This method can only be successful when the alkali salts are limited in quantity, and no one need expect to be able to rid badly charged lands from their alkali by plowing it under.
3d. By plowing under green or dry crops. If grain can be made to grow on the alkali land at all the turning under of it, either green or dry, will in course of time greatly reduce the alkali. The turned-under stubble or straw forms in decaying an acid, which in many instances will combine with and counteract the effects of the alkali. Similarly, straw stacks spread on alkali spots and plowed under will considerably reduce the alkali. But manure containing ammonia and other salts should not be used, as it will, on the contrary, only increase the alkali by adding other or similar salts to those already in the soil.
4th. Cropping. If water, either in the form of sufficient rain or as irrigation can be had, alkali lands can be reclaimed by cropping. It is amply proved that beets and carrots, as well as other plants, such as salt-bush (Chenopodium), take up large quantities of alkali salts, and in the course of a few years render alkali soils available for grain. Wheat also extracts alkalies, and repeated croppings with grain will in the course of time prepare the soil for vines and trees. Bermuda grass will completely remove the alkali from soils to the depth at which the roots can penetrate, and must be recommended for the worst places. Afterwards, cropping with annual crops may be advisable before vines are finally planted on such reclaimed lands. The Australian salt-bushes, or Chenopodium, extract alkalies, and are besides liked by stock. They should be introduced to alkali lands and take the place of the California native salt-bushes, which are not eaten by stock. While being real desert plants, they yet require some moisture in the soil, but they could probably be grown anywhere on the alkali lands in this State where the rainfall is over three or four inches.
5th. By chemicals. The use of chemicals of various kinds in counteracting the alkali is not resorted to by our farmers as it should be. The principle upon which chemicals can be used is that obnoxious or greatly injurious alkalies may be changed into less obnoxious and less injurious salts, or even into fertilizers. The most available of these chemical compounds are gypsum (sulphate of lime) and lime (carbonate of lime). When the alkali consists mainly of carbonates, such as carbonate of sodium (sal-soda) or potassium carbonate (saleratus), in other words of the class which we have designated as class number one, the most dangerous and worst class of alkalies to combat, gypsum may be used as an antidote or rather as a means to convert these alkalies into alkalies of the second class, or the sulphates. The principle upon which this is done is to displace the sulphate in the gypsum and force it to combine with the alkali (sodium carbonate) and form sulphate of sodium (Glauber salt), an alkali belonging to the third class of alkalies, and which is twenty times less injurious to vegetation than is class number one. The change is made on the following principle, and might be thus illustrated: To the alkali in the soil (carbonate of sodium), add sulphate of lime. As soon as the mixture is made with sufficient water, a change will take place, and the substances (carbonate of sodium and sulphate of lime) will form new compounds. Thus we will get, out of those two substances, two new compounds, viz., carbonate of lime and sulphate of sodium. Of these, carbonate of lime is not injurious to vegetable life, and sulphate of sodium (Glauber salt) is only injurious when present in large quantities. The carbonate of lime is not soluble in water, but the sulphate of sodium is, and can consequently be eliminated by underdraining or by flooding, as we have previously described.
To know when gypsum can be used is not necessarily a scientific matter. Mix some of the alkali in a tumbler with water, and allow the mixture to settle. In another tumbler mix some gypsum and water, and allow it to settle. Then mix the two clear liquids, which, if gypsum is an antidote and the proper thing to use, will be turbid or milky through the chemical combinations which take place. If the water remains clear, gypsum will not prove an antidote to the alkali under consideration. The use of lime is based very much on the same principle. If the second class of alkalies are present, and lime is added, the changes that take place may be illustrated as follows: Epsom salt (magnesium sulphate) combined with calcium carbonate, will form two new compounds, viz., gypsum (calcium sulphate) and magnesium carbonate, both of which substances are less injurious to crops. But, as I have already stated, raisin-vines prefer soils which are naturally free from alkali, and should never be planted on soils which cannot readily be reclaimed. Chemical antidotes may do where the alkali occurs in a few spots mixed in among tracts of good soil, but where the whole field must be reclaimed some other crop than vines had better be first attempted. There is too much good and suitable soil in California, and until all this is occupied the alkali soils had better be given up to other crops than vines.
Fertilizing.
—To this date but few grape-growers manure their soil. California has not yet been engaged in the raisin business twenty years, and her vineyards are comparatively virgin. The first raisin vineyards were planted on the deepest and richest soil, the soil which would naturally hold out the longest, but the croppings of a raisin vineyard are enormous, and when from eight to ten tons of green grapes have been taken from the soil year after year, it is but natural that the land should become gradually exhausted. In Spain it is considered that even the richest soils require manuring after ten years of constant cropping with Muscats, and the same experience is likely to become ours in California. So far, I know of not one vineyard which has yielded Muscat grapes for ten continuous years and still keeps yielding as much as formerly. Yearly the crop must become less, and finally will not be large enough to pay. The manuring of the Muscatel vines is fully understood in Spain, where all kinds of manures are used. When home manures fail in supply, the Spaniards use imported fertilizers, such as Mexican phosphates, etc. This fertilizer brings in Spain sixty-five dollars per ton, and is brought there from our very doors,—the Gulf of Lower California. It could be laid down here for, and is actually sold here now at, forty dollars per ton, or twenty-five dollars less than in Spain; still to my knowledge only very few raisin-growers in Fresno use it for their vines. In one year one of these succeeded, with the aid of this phosphate, in raising the crop of an acre of Sultana grapes from a very poor yield to over eight tons. The grapes were grown on a piece of sandy soil of the kind well known to Fresno vine-growers, and which is generally considered as less suited to raisins, lacking in fact in more than one of the necessary qualities of a good raisin soil.
It is certainly a wrong policy to crop the soil until the grape crops begin to fail. The soil will then be so exhausted of several of its ingredients, that it will take the most scientific treatment to bring it back again to what it was formerly, and it is even questionable if this could be done in a way that would prove profitable. Experience in Spain teaches that vineyards which formerly used to yield from eight to ten tons of green grapes to the acre now, after years of neglect, only yield two tons to the acre, and even with expensive manuring can in no way be brought back to their former fertility. On the other hand, we know that vineyards which have been fertilized from the beginning have for fifty years been kept up in apparently as good condition as at first; it is accordingly this method that must be recommended. The manure or fertilizer must be varied occasionally. In rotation, phosphates, bone dust, guano, stable manure, sheep manure, lime and plaster of Paris or gypsum may be used, but it is best to have every variety of soil in the vineyard analyzed, and to apply from year to year that kind of fertilizer which is particularly needed. The phosphates are those which will first give out in our California soils. Phosphates must therefore be considered as the best fertilizers we can use, but the quantity to be used must always be determined by a practical chemist. Of these chemical fertilizers, it is dangerous to use too much, as they might injure the vines, and from fifty to a few hundred pounds to the acre may in some instances suffice and produce better crops than would four or five times as much. But, regardless of chemical fertilizers, the cautious raisin-grower should endeavor to return to the soil as much as he possibly can out of the wastes of his crop. The refuse of stems and berries, which are wasted at the stemmer and in the packing-house, should not be burned, as is generally the case, but returned to the vineyard, and applied one year on one piece of ground, and another year on some other piece. If, however, these wastes must be used as fuel in the dryer, etc., the ashes should be carefully collected and spread over the soil, and kept dry and shaded until thus used.
Another most valuable fertilizer generally wasted is the trimmings. In our careless California farming, these trimmings of the vines are put in piles on the roads, outside of the vineyards, and there burned. Thus the ground loses the most powerful soluble salt, which would greatly increase the yield of grapes and the profits to the farmer. Where the vines are planted far enough apart, the trimmings may be burned between the rows of the vines without injury to them, but, when the vines are set close, there is no other way than to carefully collect the ashes and spread them evenly over the soil. Some vineyardists use large troughs made of galvanized iron and perforated with holes. These vats are drawn through the vineyard by a team, and scatter the ashes evenly over the soil. The vats may be so constructed that the cuttings are burned in them directly as they are being pulled along, thus saving much labor as well as ashes. Such contrivances will probably only prove profitable in large vineyards, where there are long rows and few turnings for the teams. Even the stable manure in our State is not used as it should be. It is hardly possible to understand how vineyardists can be thoughtless enough to haul loads upon loads of stable manure on their roads or in holes and waste places, while their vines adjoining are suffering from the want of sufficient nourishment. In the irrigated districts, this is a very common sight, and the wet places on the road are often deep with manure and strongly smelling of ammonia. If the manure had been placed around the vines, the increase in crops would probably have been sufficient to enable the owner to macadamize or otherwise permanently fix the roads.
IRRIGATION.
Introductory Notes.
—The irrigation of the raisin grapes was, for several years, considered as a practice entirely peculiar to California, but as our knowledge extended it was found that, far from being anything at all new, it had been practiced successfully for centuries in some of the Mediterranean countries. We have already mentioned how irrigation is customary both in the Valencia and Denia districts, as well as in Greece. It is evident that irrigation there is only limited by the supply of water, and that there is no question about its usefulness. As regards the methods of irrigation in these foreign countries, we beg to refer to the chapters treating of these countries. Here our efforts shall be to consider irrigation in its relation to the following points, which are of more general interest to the Californian growers: Necessity of irrigating the raisin-vines; the health of irrigated vines; the bearing quality of irrigated vines; the quality of the irrigated grape; supposed unhealthiness of irrigated vineyards; irrigation by flooding; irrigation by furrowing; subirrigation; seepage; drainage; irrigation and its influence on the soil.
The Necessity of Irrigating the Raisin-vines.
—When the irrigation of raisin grapes was first attempted in Fresno and Riverside, hardly any one was acquainted with or knew that irrigation had ever been used for such a purpose before, and irrigation was considered as a venture which did not promise well for the future. Later on it was found that the raisin grape really would grow and do well in some localities without irrigation, and the latter practice was accordingly condemned. To-day, however, the practical knowledge of irrigation is greater and more generally distributed, and it is now fully understood that irrigation is not only not injurious, but beneficial and necessary in localities where the raisin-vine will not grow or bear sufficiently without it. The questions then arose, When is irrigation necessary, and how much irrigation is required? The first object in raisin-growing is the profit; a secondary object is how to so treat the vines that they will last as long as possible. To attain the first object, we must raise plenty of grapes, and when a larger quantity of good raisin grapes can be grown with irrigation than without it, irrigation is justifiable and necessary. In Spain, especially in the Denia district, irrigation of the raisin grapes is practiced wherever water can be had, and the same is the case in Greece and Italy.
In California the tendency is now to irrigate wherever water can be had, and wherever it is profitable to procure it. In Fresno, Tulare and Kern counties, raisin grapes could not be grown without irrigation. These same conditions are also found in San Bernardino county, while in Los Angeles and Orange counties all the best vineyards are irrigated, and only occasionally do we find the conditions such that irrigation is not absolutely necessary. In Northern California, raisin-vines may be grown without irrigation, but the latter is considered of such advantage that expensive pumping works have been erected in places where no other means were had for irrigating the vines. In San Diego county, especially in El Cajon and Sweetwater valleys, irrigation is not absolutely necessary, in fact it is not practiced there at all, although water could be had, but as a consequence the crops there are not as large. In Smyrna, in Asia Minor, the largest raisin center in the world, the raisin-vines receive no irrigation, but the unusually heavy rainfall of this section makes the want of irrigation less felt. Of course, outside of the raisin districts proper, Muscatels or other raisin-vines may be grown, and are grown to good advantage without irrigation, but the climate in those places is generally unsuited to the drying of the grapes.
Should we inquire into the reasons why raisin grapes may in some localities be grown and actually prove profitable without irrigation; we find the same to depend not alone upon the rainfall of the locality, but principally upon such other circumstances as dew, fog, the nature of the subsoil, and the moisture of the air. In Smyrna the rainfall of the wet season is from twenty-four to thirty-six inches annually, and greater than in any other raisin district. In El Cajon the rainfall is only half that much, and the moisture in this case must be sought partly in the subsoil, which is especially retentive of moisture, as well as in the dew, and the warm fogs from the ocean. The subsoil has the greatest possible influence, as in other valleys near by, where the fog and the dew are the same, but, where the subsoil is different, no raisin grapes can be grown without irrigation. Malaga is in this respect very similar to El Cajon and Sweetwater valleys, but it enjoys more rainfall than the latter places, while probably the dew and fog is about the same. Still in Malaga irrigation is used in a few isolated localities where it can be obtained, the nature of that country being such, that no general irrigation system is possible, and this is probably, more than anything else, the reason why the vines are not more generally irrigated there. In Chile, in the valley of the Huasco, the Muscat vines are grown both with and without irrigation, the conditions there appearing to be very similar to those of El Cajon valley in San Diego county. From the above we might draw a general conclusion, that wherever the raisin-vines cannot grow without irrigation, and wherever water can be had in sufficient quantities, irrigation is practiced in order to increase the crops and to make the business more profitable.
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.
Irrigation by Flooding.
—This method consists of flooding the land either by means of checks and banks, which must have been constructed before the vines were planted, or in simply flooding ground which is naturally level. In either case the land must naturally not be too rough, and the water must be abundant, else this method cannot be used. It will always pay to engage the services of an engineer in preparing such ground for vines. The extra cost will be more than paid for in the first few years, when frequent irrigations of the vineyard are as necessary as they are expensive. The ditch supplying the vineyard should always run on the highest ground, and in no instance should it be run through low ground when high ground can be had, as the low ground may in the future have to be used for drainage, about which we will treat further on. From the main canal, branch ditches should run out at right angles if possible, or if the ground is very uneven they may follow the highest parts. The ground between these ditches should be properly leveled into checks. With checks the irrigator simply measures a piece of ground of any size which is surrounded by a levee or bank. This bank must be high enough to allow the water to cover all of the ground as soon as the check is filled with water from the ditch.
To make the ground level enough, it is generally necessary to level it with scrapers. The more level is the surface the better, cheaper and quicker will be the irrigation, and no small amount of trouble will be avoided if this work is properly done before the vines are planted. Too little of this leveling is done in some places, and I have seen thousands of acres planted in Muscat vines which were so improperly leveled that the profits of the vineyard in after years would be seriously interfered with. To understand how this can be possible, we must remember what takes place when we irrigate and after we have irrigated. The gate in the ditch is opened, the water flows out and runs immediately down to the lowest part of the check. When this part is reached, the check begins to fill up. If the ground is very uneven, it may take days to fill the check, and the lower part will require to be covered several feet with water before it will reach the higher parts, which always need irrigation the most. To back it up so high requires also a correspondingly high levee, which again is more apt to break and cause trouble and expense the higher it is. After the water has reached the highest possible point, the flow is shut off, and the water begins to subside. The highest part of the land becomes dry the first, and quickly, while it may take days or even weeks to dry up the lowest part of the check. When at last the check is all dry it may be found that the lowest vines have been injured or entirely drowned out. When summer irrigation is used, it is absolutely necessary to have the ground level, so that when it is flooded the water will not reach up to the grapes, as they spoil when coming in contact with the water.
The time when flooding should be used must depend upon circumstances. As a rule, flooding is especially adapted to winter irrigation, as, when the vines are entirely dormant, they may be submerged for months without suffering any harm. Young vineyards may also be flooded in summer time, but, when the grapes begin to appear, flooding can only be done in the winter or when the land is absolutely level, but even under the most favorable circumstances many grapes are always lost. Some have so prepared their vineyards that a check, when flooded, can be drained into a lower check or into a ditch. This is a very good arrangement where the land is not entirely level, as it will cause the low places to dry up as quickly as possible. But a better way is to have the ground so level that the water will sink evenly and leave no sinks nor any high and prematurely dry places. There are, however, soils so composed that the water cannot sink through them in any reasonably short time. Such heavy soils must be surface drained after every flooding, or perhaps had best be given up to some other method of irrigation. But such hard or impervious soils are frequently improved by irrigation, and in course of time lose their impervious nature and become subirrigated. If the land is tolerably level by nature, and there are prospects of subirrigation soon appearing, it may be unnecessary to level the land, and flooding with temporary checks may be used with advantage for the first few seasons. Furrowing will generally assist this mode of irrigation.
Irrigation by Furrowing.
—This method of irrigation is practiced where the land is not sufficiently level to be flooded, or when the water is not sufficient to enable the irrigator in a short time to flood the land. The practice of furrowing simply consists in plowing furrows alongside of the vines, and then to lead the water in the furrows. This system is by far the one that is most practiced in Southern California, as it has some advantages over the flooding; it is, however, not so effective and cannot supply the vineyard with as much water as flooding. To use the furrowing system to advantage, the land must have been previously leveled, but not necessarily graded to an absolute level. It is enough to have the surface smooth and on an even grade, in order that the water may run from a higher point to a lower one without spreading or breaking out. Especially all knolls in the vineyard must be leveled off, and care must be taken to fill all hollows or sinks in which the water would otherwise collect.
After the vines are planted, or when irrigation is necessary, one or more furrows are plowed on each side of the vine, and the water is allowed to run in them for several hours, or even days, until the soil is sufficiently soaked. In many places three furrows are made between the rows of vines, and the water is allowed to run in at one end and out through the other in a stream only sufficiently large to cause all the water to sink. Where particular nicety is required, the waste water which runs out at the farther end may be collected in a trough with perforated holes, through which it is conducted to a ditch or lower check. Similarly, a long trough may be used for conducting the water to the land in the first instance, and allow it to run out through a number of small holes, one of which is situated in front of every furrow. When the ground is well prepared, level and with an even slope, this system of irrigation is very perfect, and causes but little expense and trouble in management. In Riverside the vines are irrigated thus every three or five weeks, while in Redlands less irrigation is used on old vines. As a rule, in Southern California the furrowing system is the accepted one as being best adapted to the nature of the country. The water is conducted both in open ditches and in pipes, and when under pressure saves much labor and expense which would otherwise be required for the continued construction and repair of ditches.
The furrowing system has, however, its disadvantages. It requires a longer time to fill the soil sufficiently, and accordingly it takes many more irrigations to accomplish as much as with flooding. As advantages of this system, we might state that it requires no banks or levees to back up the water, and a vineyard irrigated this way can be kept entirely free from weeds by a few cultivations, while a checked vineyard must besides be cleared with hand labor, as the banks and checks are apt to be destroyed by cultivation.
Subirrigation.
—Subirrigation may be either artificial or natural. The artificial subirrigation has, as far as I know, only been used in a few vineyards in Yolo and Solano counties, the report, shortly after it had been established, being very flattering as regards its success. But of late years we have heard nothing about this kind of irrigation, and it is likely that some practical difficulty was encountered which could not be fully overcome. The artificial subirrigation consists in laying larger and smaller cement pipes between the rows of the vines. These pipes are perforated in various places, and, when filled with water under pressure, the water runs through the perforated holes and keeps the ground outside the pipes constantly moist, without causing the surface of the soil to get wet and weedy, and herein consist the principal advantages of the system, as well as in the fact that rolling ground can be irrigated thus without being previously leveled and without being cut up with open ditches. The difficulty of keeping the holes open and of preventing the roots of the vines from entering the pipes is, I understand, very great and probably impossible to overcome. Both irrigation water and liquid manures could by this system be supplied to the roots of the vines directly without any waste, and, in cases of diseases or attacks by underground pests, medicines or insecticides could be brought to the soil with the least possible cost.
The natural subirrigation is caused either by the whole soil filling up with water from the natural and original water level to the very top or to the roots of the vines, or from an impervious hardpan or clay, as subsoil, up towards the surface. As an example of the former we might cite the country around the irrigated plains of the San Joaquin valley, especially around Fresno and in Mussel Slough. Before irrigation was begun there in 1872, the surface water was from sixty to seventy feet from the top east of the railroad, and from forty to fifty feet west of the railroad, lower down in the valley. After five years of irrigation it began to be noticed that the soil required less water. The water in the wells began to rise, and the following year the water stood in many places near or on the top of the surface. Now the whole irrigated district around Fresno has filled up with water to such an extent that drainage ditches have become necessary in some places in order to lower the water in the wet season some four or five feet from the surface. Many more drainage ditches will be required, as in wet winters the surface water in places is not only very near the top, but actually forms ponds or swamps where formerly the ground was entirely dry.
In the old irrigated districts, water can now be found at from six to ten feet in the driest season, while formerly the wells had to be from fifty to seventy feet deep. In the older vineyards, and even in many of the younger ones, no more surface irrigation is used; all that is now required is to allow the water to run in the main ditches, in which the water sinks sufficiently to keep up the supply of the evaporation of the ground outside. Large tracts of land which have never been surface irrigated are now sufficiently moist to grow vines to the greatest perfection, and many of the best vineyards have never been irrigated at all; in fact, nothing but drainage ditches have ever been made on the land. Whenever such subirrigation exists, the water level will be found higher in the winter than in the summer, and drainage should accompany subirrigation in nearly every instance. A subirrigation like the above exists in Denia and other of the Spanish districts. Subirrigation may be also caused by either impervious subsoils, such as hardpan and clay, or by spongy subsoils, which keep the water like a sponge. Such is the case to a limited extent in parts of San Bernardino county. At Redlands, for instance, much less irrigation is now used than when the vines were first planted, and this fact is attributed to a spongy subsoil peculiarly retentive of water. A similar subirrigation exists in the Mussel Slough country, where the water rapidly fills the land and keeps it moist throughout the summer. The phenomenal moisture of the El Cajon land is probably also produced by some kind of subirrigation, either on impervious or through retentive strata; the waste water from the surrounding hills no doubt supplies much of the water appearing in the lower lands of the valley. Other valleys close by do not show this moisture, the underlying strata probably making subirrigation impossible with the present amount of rainfall.
Seepage.
—Seepage is the quality of the soil to attract moisture and retain it. Seepage soils attract the water from a ditch run through the land, the water spreading all through the soil towards all sides instead of sinking only vertically down. There is a distinct difference between such seepage soils and those that do not seep, although there is a gradation in the degree of the seepage, some soils seeping more than others. Thus the Fresno soil, or the soils on the Fresno plains, especially the red and sandy soils, do not seep or percolate. Vines planted on the sides of the ditches, or a foot or two from their banks, will die and dry up if not specially irrigated by bringing water to their very roots. Other soils, especially the river-bottom soils or the alluvial soils, seep or percolate in a great or less degree. They act like a sponge, attract water and give it away slowly, and the soil will be found wet for long distances from the ditch. This seepage capacity of the soil is partly caused by an abundance of humus or vegetable matter. The seepage capacity of the soil greatly increases by admixtures of green vegetable matters through the plowing under of green crops, such as alfalfa, peas, beans, grain, etc. The value of seepage soils is seen especially where some uneven ground is scraped off and the top soil removed to low places. Such ground often becomes useless for years afterwards, especially if the quantity of humus in the lower soils is small. Frequent irrigations will not serve to keep such soils moist, as the water sinks rapidly down, leaving the poor top soil dry. Vines planted in such places never do well, and even heavy manuring will not suffice to bring on a strong, healthy growth. Such humus-wanting soils must be treated with green crops, as stated above, in order to become fertile and moist. Thus seepage and subirrigation are often confounded. The former is caused by the retentive and communicative quality of the soil, while the latter is caused by the natural or artificial distribution of the underground water.
Subirrigation and seepage combined make the most perfect irrigation for a raisin vineyard, with advantages that can in no other way be attained: absence of distribution ditches, which take up valuable land and which cost money to keep clean from weeds; less growth of weeds on the surface of the ground; greater mellowness of the top soil and less work in plowing generally; a greater and more uniform supply of moisture, which, instead of being near the top of the ground, is accumulated deeper down, thus causing the roots to go down instead of spreading near the surface; no expensive irrigation, which will require plowing every time after the water is spread on the surface; a greater coolness of the ground and a lower temperature generally, which shows itself in a more vigorous growth of the vines, a greater supply of grapes and less danger from sunburn. These and many more are the advantages of subirrigation and seepage combined. To attain them in a raisin vineyard, no labor and reasonable cost should be spared.