24 BULLETIN 499, U. S. DEPARTMENT OF AGRICULTURE. 



3'ield 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 b} r 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 provide 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 rain}' season, however, all kinds of mulching material 

 break up rapidly, and in the course of a year the mulch practically 

 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. 



