24 BULLETIN 614, U. S. DEPARTMENT OF AGRICULTURE. 
regardless of the crew used, there is an annual charge fee removing 
brush of 11.46 man-hours and 11.35 horse-hours, or an acre cost of 
$4.57. 
SOIL MANAGEMENT. 
Not many years ago the orchardists of the irrigated regions were 
warned not to allow any vegetation to occupy the land between their 
trees, lest the trees be robbed of food and moisture. It was soon 
learned, however, that many of the soils of the arid and semiarid 
regions were well supplied with mineral matter, but lacked one 
element essential to the healthful and profitable development and 
maintenance of tree growth, namely, nitrogen. This lack, often 
made obvious by the condition of the trees themselves, forced many 
of the orchardists of the Northwest to resort to the use of such legumes 
as alfalfa, clover, and vetch to supply the missing element. 
It now appears that the Northwest orchardists have done much in 
solving the problem of the high cost of soil management by the intro- 
duction of these crops. Though the use of legumes is a compara- 
tively recent innovation, nevertheless the method of management of 
orchards under mulch crop now in vogue in the valley will be con- 
sidered in this bulletin. The majority of orchards considered under 
this heading have used some legeume as a mulch crop for the past 
3 to 5 years. tn 
CLEAN CULTIVATION. 
The importance of cultivation in the cost of maintenance in orch- 
ards under clean-tillage methods is shown by the fact that when all 
orchardists using this system are considered the annual cultivation 
charge per acre is $11.26, or 15.92 per cent of the total gross labor cost 
up to harvesting time. The soil of the valley is such that many men 
do not find it necessary to use the plow for breaking the land, but 
depend principally upon the disk. 
Table XVI shows the frequency with which different implements 
are used by orchardists in the Yakima district who practice clean 
cultivation. Table XIX gives the same for the Zillah district. 
TABLE XVI.—Implements and the number of or ads 6 in which each is used in 43 orchards 
under clean-cultural management in the Yakima district. 
+ | Spring- | Spike- | 6-foot . 
When used. Plow. 1 Disk _| tooth tooth culti- Suit. Float. | Crease. 
| 1atTOW) harrow. | harrow. | vator. | “2¥°- 
Before first irrigation: = -=222 52.2 29 12 22 29 26 i 8 43 
Following first irrigation. ...-. Os | ie ae eS 2 15 14 24 6 2 43 
Following second irrigation......)-....--.|...-2--- 13 10 26 5 2 41 
Hollowane Ghir Ging sop] Ones. = vaee ne seem eee ee 10 7 19 CA i ee 32 
Bollowine fourth IETie sho. 222 \eeese oe eee eee Ue Pe ain aw Roe 7 PM hss Rerae Pe ll 
Kollowine iith ann Saglome: see one |eeeeee oe | ere eet eee ete serene | epee an cee wclid oe eee oe ae 
It. is the prime object of each orchardist following this method of 
management so to till the soil that a deep mulch which will conserve 
the moisture is present throughout the growing season. (See fig. 4.) 
