94 BULLETIN 499, U. S. DEPARTMENT OF AGRICULTURE. 
yield of mulching material increased. It is not practicable, however, 
to attempt to provide all of the mulch in this way. | 
In groves planted on contours the form and size of the basins will _ 
necessarily be determined by the slope of the land. In such cases 
two smaller basins will usually be required for each tree, one above — 
and one below the tree in the row. Even in straight-row planting 
it will often be found advisable to divide the basin at the tree trunk : 
in order to insure adequate irrigation on both sides of the tree. 
Special precaution should be taken to prevent the soil forming the 
dikes from being banked against the trunk of the tree. Lemons 
appear to be particularly susceptible to bark diseases when through 
low planting or soil washing the moist soil is brought into contact 
with the trunk above the graft. 
COST OF PREPARING AND MAINTAINING THE BASINS AND THE 
MULCH. 
The initial cost of installing a basin system varies with the soil © 
and with the size of the basins. No exact figures can be given for 
all the different soil types and basin sizes, but some specific examples 
can be cited. The cost for labor alone in one grove on a sandy loam 
soil was about $18 per acre. The basins in this grove were circular 
and about 8 feet in diameter, and the grove was close planted. The 
labor cost in other groves on clay-loam soil ranged from $22 to $25 
per acre. 
The cost of the mulching material varies greatly. At the present 
writing, manure in carload lots from Los Angeles costs $2.20 per ton — 
delivered on siding in orange districts 50 miles distant. Allowing — 
15 cubic feet of manure per basin, this would cost approximately — 
50 cents per tree. One hundred and fifty pounds of alfalfa or bean — 
straw will previde a mulch equivalent to that obtained with 15 cubic 
feet of manure, and in the experimental plats has given greater — 
returns. The average yield from one block (Victoria grove) of — 
alfalfa-mulched trees was twice that of the manure-mulched trees, 
while in another block (Eureka grove) the alfalfa-mulched trees 
carried on the average 50 per cent more fruit than the trees mulched 
with manure. Barley straw costs less than either alfalfa or bean 
straw, as a rule, but in the trials here reported it has not proved so 
desirable a material for use as a mulch, and it contains, less nitrogen. 
Any mulch lasts well during the summer season, although the _ 
under portions undergo decomposition soon after being applied. 
During the rainy season, however, all kinds of mulching material 
break up rapidiy, and in the course of a year the mulch practically i 
disappears unless a fairly large quantity is used. In general it ap- 
pears that 150 pounds of alfalfa or its equivalent a year is necessary ~ 
to maintain a mulch in a basin 150 square feet in area. 
