24 



BULLETIN 614, U. S. DEPARTMENT OP AGRICULTURE. 



regardless of the crew used, there is an annual charge for 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 ^nd 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 legume as a mulch crop for the past 

 3 to 5 years. 



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 orchards in which each is used in 43 orchards 

 under clean-cultural management in the Yakima district. 



When used . 



Plow. 



Before first irrigation 



Following first irrigation . . . 

 Following second irrigation . 

 Following third irrigation . . 

 Following fourth irrigation . 

 Following fifth irrigation. . . 



29 



Disk 

 harrow 



Spring- 

 tooth 

 harrow. 



Spike- 

 tooth 

 harrow. 



6-foot 

 culti- 

 vator. 



Culti- 

 vator. 



Float. 



Crease . 



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.) 



