14 BULLETIN 499, U. S. DEPARTMENT OF AGRICULTURE. 
basins to supply mulching material. The basins in this grove were 
small and were separated in the tree row by spaces about 4 feet in 
width. These spaces between the basins were bare and unirrigated, 
the usual practice. The results of the moisture determinations pre- 
sented in Table VIT show no lateral movement of soil moisture from 
the basins into these spaces during irrigation. 
TasLeE VII.—Available soil moisture before and after irrigation in an orange 
grove having alfalfa growing in the furrow rows at Redlands, Cal. 
Available moisture after 
irrigation (per cent). 
Available moisture before 
irrigation (per cent). 
Between Between 
Depth. In| basins in in | basins 
In alfalfa | tree rows, In alfalfa |tree rows, 
basins furrow about 2 basins. furrow | about 2 
TOWS. feet from rows. | feet from 
basins. basins. 
Birst fOObe sae eee ee ee Ao —1.4 0.9 ld: 4.9 —0.7 
BECONGHOO ES os ene eam ee 4.8 .6 1.8 6.4 8 1.1 
MET 1OOb eee ee eo oe ee Oh a 5.1 i al 5.5 1.0 2.4 
HOUTLEMOOL? Sp acne eee te oR cay oa ee 4.3 4 2.9 4.9 1.9 Sot 
AVCTAC Ow eta sucked aera ORE Ree 4.6 — .4 1.9 5.6 2.2 1.5 
SUMMER COVER CROPS IN GRANGE GROVES NOT PRACTICABLE 
WITHOUT AN INCREASED WATER SUPPLY. 
The moisture conditions in the alfalfa furrow rows as shown in 
Table VII are quite typical of conditions found in other orange 
groves with alfalfa growing between the trees. In 1914, soil samples 
were taken in three groves of this kind after irrigation, and the 
moisture had penetrated only from 10 to 30 inches after a two or 
three days’ run of water. The large amount of water removed by 
such crops and the bad effect on the orange trees of the competition 
with the cover crop have already been mentioned in connection with 
the experiments in the Victoria and Vivienda groves. With the 
amount of water usually available for irrigation in these districts 
(1 miner’s inch to 5 acres), no summer cover crop of any kind can 
be grown in citrus groves in the areas studied without causing dete- 
rioration of the trees. Instances were found where summer crops, 
such as buckwheat and sweet clover, were grown quite regularly, 
but in these cases there was plenty of water available for both trees 
and cover crop. 
ORGANIC MULCHES MORE EFFECTIVE THAN SOIL MULCHES IN 
CONSERVING WATER. 
Four cylindrical cans 24 inches high and 18 inches in diameter 
were filled with soil from the Victoria grove on June 25. The soil in 
the different cans was treated as follows: (1) Surface soil kept 
