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UNIVERSITY OF CALIFORNIA AGRICULTURAL EXPERIMENT STATION
/.«..-«- ^- .__.*.. .._..__ BENJ. IDE WHEELER, President
COLLEGE OF AGR CULTURE
& VF MVaPI,v ' , -' , - , ur,c - THOMAS FORSYTH H U NT, DEAN AN D DIRECTOR
BERKELEY h. e. van norman, vice-director and dean
University Farm School
CIRCULAR No. 194
INTERCROPPING OF YOUNG
By E. S. VAILE
More California orchards were intercropped during 1917 than ever
before. The desire to produce more actual food during the present
war emergency, and the added desire to share in the prevailing high
prices contributed to this result. An exhaustive survey, made through
the agencies of the various marketing associations, the County Horti-
cultural Commissioners, and Farm Advisors, indicates that where
normally only about 25 per cent of the irrigated orchards under six
years of age are intercropped; this year, 1917, at least 45 per cent
have been so handled. Going more into detail, the percentage of
orchards, three years old and under, intercropped has increased from
33 per cent to 50 per cent, while the percentage of intercropped
orchards from three to six years of age has increased from 20 per cent
to 40 per cent.
The survey indicates that out of some 77,000 orchard acres of
young citrus in southern California 30,000 acres have been planted
to beans, 3000 to grain sorghums, 1000 to corn, 2000 to potatoes., and
one or two thousand to miscellaneous crops. About the same per-
centage holds for the irrigated deciduous orchards of southern Cali-
fornia and very nearly the same ratio of crops used. In the San
Joaquin Valley the amount of intercropping is not so large and grain
sorghums occupy almost an equal place with beans.
This paper is based on a field study of, first, the results obtained
with the increase in intercropping, and second, the possibilities of even
further extension in the future. Young orchards only are considered.
The intercropping of bearing orchards is a practice which has been
dismissed in the past as being both agriculturally unsound and
financially unprofitable, under the ordinary California orchard con-
ditions. The evidence seems conclusive that there is nothing in the
present situation to justify a change in this general attitude.
The intercropping of unirrigated orchards is too hazardous for
consideration, both agriculturally and financially, except in a few
locations where the minimum rainfall is sufficient to insure satis-
faction to both crops.
The man who is intercropping an irrigated orchard has certain
very definite economic advantages over the man who is raising a crop
in an open field ; namely :
1. The orchard pays the land rental charges including interest
and taxes ; the intercrop does not have to meet that expense.
2. The usual practice in irrigated orchards that are not inter-
cropped is to work up the land thoroughly in the spring and keep it
cultivated during the summer; thus the intercrop need not pay the
expense of preparing the land for planting.
3. The arrangement of many irrigation projects provides for the
delivery of sufficient water to support full bearing orchard trees;
there is no saving in cash payments for water in certain cases if less
than the total amount is used ; it takes no more water to care for young
trees and an intercrop than it does for full bearing trees ; therefore,
in these cases the water for irrigating the intercrop is not properly
chargeable to that crop.
4. Very often orchardists have unused time of both themselves
and their teams, which can be turned to good service in the planting
and care of the intercrop ; in which case the entire labor cost is not
properly chargeable to the intercrop.
In other words, the additional expenditures connected with inter-
cropping orchards, are mainly reduced to the cost of seed, a possible
slight charge for cultivation during the growing season, the harvesting
costs and, sometimes, a charge for additional water.
On the other hand, intercropping is by no means a "get rich
quick" scheme. Success with intercropping depends upon how and
under what conditions it is done. No crop, whether an intercrop or
one in the open field, can be better than that allowed by the weakest
of several factors necessary to its production, namely: the farmer;
the soil ; the climate ; the moisture supply. The first requirement,
therefore, is to choose that crop which the farmer himself knows some-
thing about. As a secondary consideration, this crop must be adapted
to the soil and climatic conditions under which he is working ; and an
abundant moisture supply both for the intercrop and the trees must
be assured. An off season may even then result in partial or total
The point which most often leads to failure with intercropping is
the fact that the grower overlooks the necessity of caring for each of
the two crops just as religiously as though it were growing alone. If
this is not done, one or the other crop is sure to suffer.
Certain crops, particularly the cereals, are notably hard in their
effects on soil productivity. When they are used as intercrops, there-
fore, more than the usual amends must be made. With grain hays
the soil is frequently allowed to become excessively dry just at the
time of ripening of the hay. Orchards are very apt to suffer because
of this factor. Grain stubble left standing in the field during the hot
weather of early summer is liable to cause severe sunburning of
orchard trees, apparently through the intense heat reflected, as well
as because of excessive drying out of the soil.
Harvesting of various crops is apt to interfere with orchard work,
both in point of time and by enforced tramping of wet ground.
At present the market will hardly be a limiting factor except in
case of less than car lots of perishables. Non-perishables and car lot
shipments can always be disposed of at better than pre-war prices.
There are three especially important considerations in the inter-
cropping of young orchards; namely:
1. The maintenance of the productive condition of the soil;
2. The financial returns from the crop ;
3. The distribution of labor between the orchard work and the
MAINTENANCE OF THE PRODUCTIVE CONDITION OF THE SOIL
In considering these points it is necessary to keep in mind the fact
that all of our semi-arid irrigated land is confronted by the very
serious problem of maintaining the organic matter of soils. Just at
present, there is a rapid decrease in the available supply of barnyard
manure, and also a growing tendency on the part of bean growers to
utilize bean straw directly on their own land. The value of alfalfa
hay and even cereal straw for feeding purposes is so high now as to
be almost prohibitive for soil improvement purposes. Therefore, it
seems particularly desirable that leguminous green manure crops be
used in all orchards. In other words, intercropping should not inter-
fere with the common practice of raising a winter green manure crop
which ma}' be plowed under in the early spring. Summer green
manure crops may occasionally be substituted in cases where winter
crops such as cabbage are distinctly the most profitable cash crops
which could be grown on the land. Ample water for the summer
green manure crop would need to be assured in such cases.
The organic matter problem immediate^ suggests the possibility
of growing a strip of alfalfa between the young trees for a period of
years, a part of which may be used for soil improvement around the
trees. This is entirely feasible on well drained soils where ample
water is available. Ample water in this conection will usually mean
irrigation once every two weeks through the growing season, with a
total of at least 50 per cent more water than would be used on the
same soil for the trees and an intercrop of beans. Trees growing on
heavy, poorly drained soil have frequently shown injury from the
large applications of water used on the alfalfa and therefore, great
caution must be exercised with this combination planting.
Beans, corn, sorghum, potatoes, and many of the short seasoned
vegetable crops may be raised during the summer without interfering
with winter green manuring.
The immediate effect of intercropping on the growth and appear-
ance of orchard trees may be taken as indicative of the effect on soil
conditions. This effect may appear as an actual improvement in the
trees, showing that the practice need in no way interfere with the
yield or development of the orchard, provided the proper crop and
the proper system of management are undertaken. Out of several
hundred inquiries, no one was found who felt that beans, for instance,
injured young trees when grown as an intercrop. Several felt that
they would not plant beans, particularly in the San Joaquin Valley,
because they felt there was too small a margin of profit in the under-
taking, not because of interference with tree growth. In fact the ex-
perience of years in commercial bean growing in California indicates
that the soil is not noticeably injured for a long period of time, par-
ticularly if the bean straw is returned to the soil and many growers
feel that the land is actually improved by the cultural methods neces-
sary for good bean production.
Numerous instances were found where other crops than beans
showed an immediate effect upon tree appearance and growth. A
study of such cases indicates three principal factors contributing to
this effect ; namely, competition for nitrogen ; competition for moist-
ure ; and puddling of the soil. The evidence seems perfectly clear that
the first two of these factors can be overcome by avoiding planting
too close to the trees and by maintaining an ample moisture supply
in the uncropped strip near the trees. The exact distance at which it
is safe to plant cannot be given. Local experience and the best judg-
ment of the farmer must dictate that. Give the benefit to the tree
rather than to the intercrop, when in doubt. The third factor may be
avoided by not planting crops which require tramping of the ground
when it is wet.
It is impossible to discuss the question of cash returns without
presupposing a definite yield. The yield will vary with the condition
under which the crop is grown. For certain sections of the state,
potatoes will give the largest cash return, while in other cases it will
be beans and in a few cases, corn or grain sorghum. It is even more
difficult to consider the cash returns that might come from vegetable
growing, because in that particular case the skill of the farmer is of
importance out of all proportion to any other factor.
A few illustrations may be taken from this year's experience with
intercropping of young orchards which will indicate the possibilities.
A certain farmer in the Yucaipa Valley who was an experienced potato
grower intercropped a considerable acreage of young apple orchards
with potatoes. He had one-half to three-eighths of the land in
potatoes, thus leaving a considerable strip along the tree rows as a
protection against injury to the trees. He harvested an average of
110 sacks per orchard acre, which he sold at $3.00 a sack. His extra
water cost was $1.00 per acre. His only other extra costs were seeding,
cultivation of the potatoes and the harvesting, which were, of course,
not higher than similar costs would be on open ground. A certain
farmer in the cabbage section in Orange County grew last winter five
tons of winter cabbage to the orchard acre. Following the harvesting
of the cabbage, he planted Black Eye beans in late June and harvested
twelve sacks per orchard acre. His gross returns were approximately
$150 per acre. The owner of a young walnut orchard in Ventura
County has for the past two years raised 3000 pounds of Henderson
bush limas per orchard acre. This year he sold his beans for 12c a
pound, or a gross return of $360 per orchard acre. A walnut grower
in El Monte turned under a green manure crop in February, 1917.
In June, he harvested seventy-five sacks of potatoes and in October he
threshed twelve sacks of Black Eye beans to the orchard acre. Total
gross returns about $260 per acre. In a two-year-old citrus orchard
near Santa Ana, the owner raised sweet potatoes which he sold for $400
per orchard acre yield. These followed a winter green manure crop,
but they were matured early so as to take advantage of high prices.
These are, of course, the results obtained by particularly good farmers
working under favorable conditions.
A summary of the records of yields of intercropped citrus land,
covering several hundred individual instances, shows that one should
expect from an orchard acre of three-year-old trees or younger,
60 per cent of the yield which he would get from an open field acre
under like soil and climatic conditions, and 50 per cent of a normal
open field yield in orchards from four to six years of age, inclusive.
Walnut groves will do better than this because of the great distance
between the slow growing trees. A 50 per cent yield may often be
obtained in a ten-year-old orchard where the trees are sixty feet apart.
Plantings in apricot orchards, on the other hand, will not do so well
as those in citrus. In fact, intercropping probably will not be profit-
able after the apricot trees are four years old.
RESULTS AT CITRUS EXPERIMENT STATION FARM
The following statement of the results with intercropping sixty
acres of the Citrus Experiment Station property at Riverside with
Black Eye beans many be taken as typical of what may be accomplished
even when conditions are below normal to begin with.
The laud in question had been cropped to grain hay for many years. So far
as known, it had never been planted to any other crop prior to this year, nor had
it ever been irrigated. In 1915, one ton of oats per acre was harvested from a
part of the tract, the remainder being untilled that season. Following this crop,
all the land was deeply plowed and nothing was planted during 1916.
The property was planted to citrus trees during the months of May and June,
1917, with the trees placed 20 X 24 feet apart. A narrow strip of land in the tree
row was plowed at the time of planting. The rest of the ground was unworked
until preparation for bean planting was commenced.
For bean growing, the land was double-disced with tractor and 12-inch disc
two ways and harrowed; four and one-half acre inches of water was applied in
furrows fourteen inches apart; the land was double-disced again and seed planted.
The seed was planted with bean planter, rows being thirty-six inches apart, with
six rows between the trees, occupying three-fourths of the ground. The dates of
planting were from June 7 to 26.
Two irrigations were necessary after planting, one, July 23, and one, August
15. Cultivation was done with a modified Planet Jr. cultivator, having two sweeps
to the row and cultivating two rows at a time.
In addition to the beans, a single row of dwarf milo was grown in the tree
rows. The heads have been harvested and the stalks used to tie up the trees as a
prevention of frost injury during the winter. The grain produced will easily pay
for the cost of growing the sorghum and tieing the trees
Cost of EaisinOt Crop of Black Eye Beans at Citrus Experiment Station, 1917
Orchard acre Full
(J of an acre) acre
Double-disced and harrowed two ways (tractor) $ .68 $ .90
18 pounds @ 12V 2 c 2.25 3.00
Two row bean planter .27 .36
4% acre inches — one full acre @ 30c per acre
Labor of irrigating .37
Cost of one irrigation, per acre $1.72
Total of three irrigations, one before and two after
planting 3.87 5.16
Furrowing for irrigations (three), 32c per acre .96 1.26
Cultivations (three) @ 36c 1.08 1.44
One hoeing @ 10c 08 .10
Twelve orchard acres per day, one man, two horses,
$4.00 33 .44
Three men, twelve acres per day, @ $7.50 63 .84
Hauling to stack 80 1.07
Feeding from stack to thresher 31 .41
7% sacks per acre @ 35c per sack 2.63 3.51
New sacks and stencilling, 7% sacks per acre @ 15c
per sack : 1.12 1.50
Cleaning @ lie per 100 lbs. — 595 lbs 65 .87
Orchard acre Full
(^ of an acre) acre
Freight to cleaning house
595 lbs. @ $2.15 per ton 07 .09
Total cost $15.73
Credit, 540 lbs. beans @ 8%c 45.90
19 lbs. split beans @ iy 2 29
Less cost 15.73
Net profit $30.4;i $40.64
The only orchard costs for the period June 7 to September 17, not charged
directly to the bean crop, were as follows:
Water for the trees, 8 acre inches @ 30c * $2.40
Cultivation for trees, including furrowing out, one horse Avork 1.65
Total per acre $4.05
It should be borne in mind that had these beans sold for 4c (a good pre-war
price for Black Eye beans) the gross returns would have been only $21.60, and
tbe net profit $5.87. Even this would have paid all the other orchard costs for the
summer and left $1.87 per orchard acre as a margin of net profit. On the other
hand, the cost of $4.05 per acre, charged against the trees might have been
increased somewhat had the grove been clean cultivated.
ADJUSTMENT OF LABOE REQUIREMENTS
Choice of intercrops should be made with due consideration to the
labor requirements of both the orchard and the intercrop. For in-
stance, the planting of the intercrop should be so planned that the
supply of man and horse power at hand may be turned directly from
the rush of spring orchard work to the preparation of land and plant-
ing. Similarly, the time for harvesting the intercrop should be
planned to avoid the stress of fruit harvest so far as possible. Much
of the work connected with the intercrop may be handled by the
regular labor supply in time which might not otherwise be gainfully
employed, unless such coordination is worked out. Black Eye beans
may be planted, in the interior localities at least, any time from the
middle of May to the first of July, with every reason to expect a satis-
factory harvest. The time of maturing in the interior is about ninety
days on the average. The following table gives the planting and har-
vesting dates of Black Eye beans on the Citrus Experiment Station
farm at Riverside, 1917 season.
Effect of Different Dates of Planting on Growing Days of
Black Eye Beans
Planting Cutting Days E'irst Dates
date date growing irrigation irrigated
May 12-14 Aug. 20 100 Early in July
June 7-8 Sept. 3 88 July 25-28 Aug. 15,16
June 22 Sept. 16 86 July 23-28 4 Aug. 22-24
June 26 Sept. 19 85 July 29 Aug. 27
June 28 Sept. 21 85 Aug. 1-2 Aug. 30-31
July 10 Oct. 2 84 Aug. 10 Sept. 5
July 19 Oct. 9 82 Aug. 3
Average of season's planting, 87 days.
Potatoes, if planted for the spring crop, should be in the ground
before the 10th of March, and may then be harvested by the middle
of June. This means a rush of work following the turning under of
the cover crop. Fall potatoes are apt to compete in point of time with
the proper planting of a winter cover crop following their harvest.
DISCUSSION OF CROPS
As mentioned in the introduction, beans, grain sorghum and pota-
toes have been the principal intercrops used during the past season,
with beans easily the favorite. Some of the advantages and require-
ments of these crops have been mentioned in illustration of various
points relative to intercropping. The reason for the predominance of
beans may be summed up briefly as follows : they are not hard on
the soil and may even be a benefit to the orchard ; the water require-
ments are easily met without interference with orchard irrigation ; the
product is non-perishable, of high food value, and can be shipped
anywhere ; varieties may be found adapted to almost every condition
and the cultural requirements are, in general, well understood.
Spring potatoes follow a winter cover crop admirably, provided the
labor requirements can be adjusted. Usually no extra water is re-
quired for this crop, beyond what would normally be used for the
orchard. As an illustration, American Wonder potatoes were planted
on the Citrus Experiment Station farm at Riverside in late Febru-
ary, following the plowing down of a Melilotus crop. They were irri-
gated twice and harvested in June, yielding 125 sacks per solid acre.
A crop of early amber sorghum followed the potatoes and was har-
vested for hay to make way for another winter crop of Melilotus. Fall
potatoes, on the other hand, require irrigation at least once every two
weeks for the first six weeks after planting.
Grain sorghums give good promise in the interior sections, although
they are not of equal cash value per acre to either beans or potatoes.
The labor requirements are relatively low, but the growing season is
long compared to that for Black Eye beans.
There are certain other crops which are occasionally used as inter-
crops. A few of these will be briefly mentioned.
Tomatoes are desirable if the marketing facilities are good. Fre-
quently, however, unless there is a cannery to absorb the surplus, the
market conditions are such that no profit is realized from this crop.
There is the injurious factor with tomatoes of constantly tramping
the ground during the picking.
Cantaloupes may be raised, but in most cases it is impossible to
compete with the Imperial Valley and the Fresno cantaloupe sections.
Casabas give a fair market return but are \ery frequently ruined
Winter peas if grown for the December trade are always at a
premium price. They have a very high labor requirement at the time
of picking. This, however, comes at a time when orchard labor re-
quirements are relatively low. There is the disadvantage with this
crop of tramping the ground while it is wet during the picking
season. There is the advantage that the vines themselves form the
winter green manure crop following the harvesting of the pods. The
growing of peas for the canneries is not a feasible proposition except
where canneries are equipped for handling peas through the viner
method. Peas are subject to attacks of aphis and damage by mildew.
Sweet potatoes fit in nicety with orchard requirements where the
soil is adapted to sweet potato culture. This is one of the most profit-
able crops in the whole list of annuals in California, but it is adapted
to a comparatively small range of soil conditions. Sweet potatoes are
difficult to keep in storage.
Vegetable growing is a specialized art and only those familiar
with it are apt to succeed. Market conditions are often uncertain
although some things may be sold on contract in advance of growing.
This applies particularly to such crops as spinach, peppers, and
tomatoes for the canners. The opinion of one very practical orchard-
ist on this point of vegetable growing is quoted as follows: "The list
of possible vegetables is produced by the regular gardeners to the
extent of barely remunerative prices. The average man, unskilled in
the growing of these things, working with conditions not the best, I
fear, would discredit the whole thing. Satisfactory crops of vege-
tables as a rule need enriched soil all to themselves. It seems that the
constant going over the land with irrigation and tramping over it
gathering vegetables, does not leave the land in good physical con-
Remember, in intercropping, that two crops are being raised and
that each one needs the same sort of attention as if it were growing
Rely on the most successful general farming practice of the com-
munity for choice of crops and cultural methods. Crops which are not
successful in open field farming in the district will be failures as
Arrange for the upkeep of the organic matter content of the soil
through the use of legumes to be turned under and the use of other
forms of organic matter.
Avoid crops which necessitate tramping of wet ground or which
call for excessive irrigations.
Plant orchards to beans (unless some other crop is definitely better
adapted) wherever there is a reasonable expectation that the crop
wiU pay for the additional expenditures.
STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION
Appendix to Viticultural
1897. Resistant Vines, their Selection, Adaptation, and Grafting.
Report for 1896.
1902. Report of the Agricultural Experiment Station for 1898-1901.
1904. Twenty-second Report of the Agricultural Experiment Station for 1903—04.
1914. Report of the College of Agriculture and the Agricultural Experiment Station.
1915. Report of the College of Agriculture and the Agricultural Experiment Station.
1916. Report of the College of Agriculture and the Agricultural Experiment Station.
1917. Report of the College of Agriculture and the Agricultural Experiment Station.
Etiological Investigations. 271.
Vine Pruning in California, Part I. 272.
Humus in California Soils. 273.
Vine Pruning in California, Part II.
The Economic Value of Pacific Coast 274.
The Loquat. 275.
Utilization of the Nitrogen and Organic
Matter in Septic and Imhoff Tank 2 76.
Deterioration of Lumber. 278.
Irrigation and Soil Conditions in the 2 79.
Sierra Nevada Foothills, California. 280.
The Citricola Scale.
New Dosage Tables. 282.
Melaxuma of the Walnut, "Juglans
Citrus Diseases of Florida and Cuba 284.
Compared with Those> of California. 285.
Size Grades for Ripe Olives. 286.
The Calibration of the Leakage Meter. 288.
Cottony Rot of Lemons in California.
A Spotting of Citrus Fruits Due to the 290.
Action of Oil Liberated from the Rind.
Experiments with Stocks for Citrus. 291.
Growing and Grafting Olive Seedlings.
A Comparison of Annual Cropping, Bi-
ennial Cropping, and Green Manures
on the Yield of Wheat.
Feeding Dairy Calves in California.
Preliminary Report on Kearney Vine-
yard Experimental Drain.
The Common Honey Bee as an Agent
in Prune Pollination.
The Cultivation of Belladonna in Cali-
Irrigation of Rice in California.
Irrigation of Alfalfa in the Sacramento
Trials with California Silage Crops for
The Olive Insects of California.
Irrigation of Alfalfa in Imperial Valley.
The Milch Goat in California.
Potash from Tule and the Fertilizer
Value of Certain Marsh Plants.
The June Drop of Washington Navel
The Common Honey Bee as an Agent
in Prune Pollination. (2nd report.)
Correspondence Courses in Agriculture.
Increasing the Duty of Water.
Grafting Vinifera Vineyards.
Some Things the Prospective Settler
Alfalfa Silage for Fattening Steers.
Spraying for the Grape Leaf Hopper.
The Control of Citrus Insects.
Spraying for Control of Walnut Aphis.
County Farm Adviser.
Official Tests of Dairy Cows.
Wood Decay in Orchard Trees.
The Silo in California Agriculture.
The Generation of Hydrocyanic Acid
Gas in Fumigation by Portable Ma-
The Practical Application of Improved
Methods of Fermentation in Califor-
nia Wineries during 1913 and 1914.
Practical and Inexpensive Poultry Ap-
Control of Grasshoppers in Imperial
Oidium or Powderv Mildew of the Vine.
Tomato Growing in California.
Round Worms in Poultry.
Feeding and Management of Hogs.
Some Observations on the Bulk Hand-
ling of Grain in California.
Announcement of the California State
Dairv Cow Competition, 1916-18.
Irrigation Practice in Growing Small
Fruits in California.
How to Operate an Incubator.
Control of the Pear Scab.
Home and Farm Canning.
Lettuce Growing in California.
Potatoes in California.
White Diarrhoea and Coccidiosis of
Small Fruit Culture in California.
Fundamentals of Sugar Beets under
The County Farm Bureau.
Feeding Stuffs of Minor Importance.
Spraying for the Control of Wild Morn-
ing-Glory within the Fog Belt.
The 1918 Grain Crop.
Fertilizing California Soils for the
Farm Drainage Methods.
Progress Report on the Marketing and
Distribution of Milk.
Hog Cholera Prevention and the
Control of the California Ground
Extending the Area of Irrigated Wheat
in California for 1918.
Infectious Abortion in Cows.
A Flock of Sheep on the Farm.
Beekeeping for the Fruit-Grower and
Small Rancher, or Amateur.
Poultry on the Farm.
Utilizing the Sorghums.
Agriculture Clubs in California.
Pruning the Seedless Grapes.