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.

[Illustration: Raisin-grape Picking at Riverside.]

_Drainage._--Drainage is necessary in all vineyards where large

quantities of water are used for irrigation, and principally at the very

time that subirrigation begins. Thus in Fresno county the best raisin

vineyards are those in which the land is both subirrigated and drained.

When irrigation commences in any certain district, no one thinks of

drainage as a possibility, and great carelessness is shown in locating

ditches and other irrigation works. But in a few years, when the soil is

full of water which finds no outlet, drainage becomes both necessary and

desirable. A very successful and highly necessary drain has been

constructed through a part of the Fresno district, which so filled up

with water during the rainy winter of 1883-84 that much of the ground

could not be plowed until late in the spring. The drain remedied the

evil and drained the soil, and the vineyards grown there are now counted

among the best and most profitable. The water thus drained off lowered

the water level from six to seven feet. In very dry seasons this ditch

is filled with water, and serves then to keep the soil moist through

seepage or subirrigation.

_The Influence of Irrigation on the Soil._--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.