24 BULLETIN" 518, U. S. DEPARTMENT OF AGRICULTURE. 



with spike-tooth harrows. These tools are usually light, the aim be- 

 ing not to cultivate deep, but to keep a mulch on the soil and keep the 

 orchard free from weeds. Each tool is often run " both ways," and 

 frequently is zigzagged to form a " figure eight " about the trees. 



Eilling the orchards for irrigation is discussed under " Irrigation," 

 but is charged to cultivating time. In the case of the orchards, under 

 mulch crop, the crop is sown usually during the surmner and is left 

 down for a varying number of years. It is not necessary to reseed 

 unless the orchard is plowed up and cultivated, thus killing the crop. 

 The practice of turning the mulch crop under annually, common in 

 the East, is not general here. A^Hien these orchards are plowed up 



Fig. 8. — The common type of weeder used in cultivating. The driver rides, his weight 

 helping to force the knives into the soil. The tips of the branches of the young trees 

 are being sprayed for aphis. 



and cultivated, about the same general system is followed as in the 

 case of the orchards which are clean cultivated annually. Orchards 

 in alfalfa usually are disked every spring; sometimes a spring-tooth 

 also is used. 



The average time required for the different operations in cultiva- 

 tion was in each instance more in the case of mulch-crop orchards 

 than in those under the clean-culture system. As will be seen in 

 Table VII, the cost of disking an acre once over is about the same 

 for both types of management, but there is a difference of $0.18 per 

 acre in the case of the spring-tooth, $0.03 per acre for the spike-tooth, 



