22 
Citrus and Tropical Fruit Culture 
and later, as the feeding roots reach the center of the 
space between the rows, the entire space should be 
furrowed out and irrigated. Care should be exer- 
cised at all times to see that the water is run a suffi- 
cient length of time to thoroughly wet the sub-soil, 
thus enabling the root system to stay well below the 
surface. In light sandy soils, the water will sub- 
irrigate sufficiently while running through the rows, 
or at least within 30 minutes to one hour after reach- 
ing the ends, but in the heavier soils it requires a 
much smaller stream to each row and the time re- 
quired to thoroughly wet the sub-soil varies from one 
half day to as much as three or four days, the latter 
time only being required on the very heaviest clay 
soils where there is a considerable slope to the land. 
What is known as the basin system is used on 
very light level lands. This method should never be 
applied only where the soil is sufficiently porous, so 
that the water will not stand in the basins but a few- 
minutes after they are filled. In this system, ridges 
Are run both ways, dividing the land off into blocks 
or squares, usually one tree to a square, and a ditch 
or furrow is made between the rows to convey the 
water to the squares. As each square is filled the 
water is shut off and carried to the next, usually be- 
ginning at the lower end of the orchard and working 
up to the head. We do not recommend this system 
excepting where the soil is so loose and level that the 
furrow system is impracticable. 
Citrus trees do not usually require irrigation dur- 
ing the winter months. The rainfall generally is 
sufficient for their winter requirements. However, 
it sometimes happens that through lack of rain they 
require a light irrigation or two during the winter 
or spring. Three to five irrigations during the sum- 
mer months are the average requirements necessary 
to keep a mature orchard in proper condition. 
The proper cultivation of the orchard is equally as 
important as the irrigation and the full value of the 
irrigation cannot be conserved if the cultivation is 
delayed or improperly done. The requirements of 
the different soils vary as to time and manner of 
cultivation. A light sandy soil can be worked in 
about 24 hours after the water is shut off, while the 
heavier clay soils should be allowed to dry from two 
to five days, depending on the weather before culti- 
vating. On soils of this nature it is advisable to fill 
in the furrows with a harrow just as soon as the 
surface shows signs of baking or crusting over. By 
doing this the cultivation can be delayed for two or 
three days or until the soil below is sufficiently dried 
so that it will not stick together or turn up in solid 
masses. Avoid cultivating heavy soil when it is too 
wet, as it not only dries out much faster, but makes 
it more difficult to work in the future. 
The main idea in cultivation is to pulverize the 
surface soil, so as to form a mulch fine enough to 
prevent the sub-soil from drying out. If left loose 
and cloddy much of the good is lost and irrigation 
will be necessary again in a much shorter time. It is 
customary to cultivate the ground from two to eight 
times after each irrigation, going in a different direc- 
tion each time, so as to thoroughly pulverize it on 
all sides of the trees. Each cultivation should be a 
little deeper than the preceding one so that when the 
work is completed there will be a mulch of fine soil 
from 4 to 6 inches deep. By starting shallow and 
going a little deeper each time it tends to pulverize 
the soil better and in heavy land prevents it from 
breaking up in large clods. These cultivations should 
not follow each other closely, but at intervals of 
from two to four days after each two cultivations. 
During the winter months, if it is desired to keep 
the orchard clean, the ground should be cultivated 
after each rain and at this time of year it is not as 
necessary to pulverize the soil ; in fact it is better to 
leave it a little rough so that the rains will have a 
chance to soak in. 
The practice of sowing winter cover crops or of 
leaving the natural vegetation grow during the win- 
ter months, is being quite extensively followed now, 
and as most of our California soils are deficient in 
humus, it gives quite satisfactory results, where prop- 
erly handled in the spring. In following this plan it 
is always advisable to leave the orchard furrowed out 
for irrigation so that in case of a shortage of rain 
during the winter or spring, an irrigation can be 
given the trees whenever necessary. The cover crop 
should be turned under with a plow as early in the 
spring as possible. It is not advisable to plow or cul- 
tivate very deep just before or during blooming time, 
and if the cover crop cannot be plowed in before 
this, it is better to wait until after the fruit is set and 
then work it up with a disc, but in this case it will 
be necessary to keep the ground well watered so that 
the trees will not suffer during the blooming period, 
as at this time the energy of the tree is taxed to the 
limit, and the root system needs all the help possible 
to support the top in its effort to set a crop. 
FERTILIZATION 
The many different soil conditions in California 
makes it impossible to lay down any set rules for this 
most important factor, but it is a matter that should 
have the attention of the planter before the orchard 
begins to show that it is in the need of plant food. 
It is much more difficult and costly to bring an or- 
chard back into condition, once it has suffered from 
the lack of fertilizer, than it is to keep it thrifty by 
adding plant food as the available supply is being 
consumed. 
The three chemicals necessary in the soil to sus- 
tain plant life are nitrogen, phosphoric acid, and 
potash. All our soils contain these ingredients, but 
not always in available forms or sufficient quantities 
to grow trees successfully, and never is the supply 
great enough to last indefinitely, hence sooner or 
later the artificial appliaction of plant food must be 
resorted to. 
It is best to start in while the trees are young and 
