MULCHED-BASIN SYSTEM OF IRRIGATED CITRUS CULTURE. 13 
FURROW IRRIGATION OFTEN NOT ADEQUATE. 
The furrow system of irrigation often fails to provide the moisture 
necessary for good growing conditions for orange trees in the heavier 
types of soil. This was strikingly shown during the season of 1915, 
many orange groves wilting between irrigations. At one time dur- 
ing the summer a grove adjoining the Victoria grove showed wilt- 
ing for several days before irrigation. Soil samples were taken at the 
time to determine the percentage of moisture present. The results 
are shown in Table VI, the moisture-determination figures represent- 
ing the average moisture content to a depth of 3 feet of soil. 
Taste VI.—WMoisture conditions under wiited orange trees. 
Av rage moisture. 
Moisture | Wilting 
Condition of leaves. equa: coeffi- 
ent. cient. Availa- 
In soil Bias 
| Per cent. | Per cent. 
FAulsleaviesion treeibadilywilltediseea-receee cee eatin coeeiecee cece 15.6 8.5 6.9 —1.6 
Leaves on top third of tree badly wilted, lower two-thirds not 
ROVE G lee Ra RU SN a peat op Ve A i ee Se 8.2 Uoal —.i 
The moisture determinations include the dry surface soil, which 
through surface evaporation dries out to about one-half the wilting 
coefficient, so that the average moisture content of the 3-foot section 
is about nine-tenths that of the soil actually occupied by the tree 
roots. The second tree mentioned in Table VI had been wilted for 
several days preceding the sampling. These observations on heavy 
soil and similar observations on light soil show that the wilting 
coefficient determined indirectly from the moisture equivalent of a 
soil agrees satisfactorily with direct determinations made in the 
groves. 
LATERAL MOVEMENT OF SOIL MOISTURE VERY SLIGHT. 
The lateral movement of moisture in the heavy soils of the Vic- 
toria tract is very slight. After an irrigation considered sufficient 
to last about 28 days, the moisture was found to have penetrated 
laterally only about 18 inches from the irrigation furrow. In other 
words, there is practically no lateral movement of water toward 
the tree, the feeding roots being confined to the soil below the irri- 
gation furrows. 
The lateral movement of water was also found to be very slight in 
a basined grove at Redlands located on the same type of soil as the 
Victoria grove just discussed. Soil samples were taken on May 26, 
before the first spring irrigation, and the day after the grove was 
irrigated samples were again taken within a few inches of the first 
samples. Alfalfa was being grown in the furrows between the 
