10 



BULLETIN 338, U. S. DEPARTMENT OF AGRICULTURE. 



The approximate cost of new spring-tooth harrows of the average 

 sizes shown in Table IV is $17.50. The replacement cost for each 

 time an acre is harrowed with the spring-tooth harrow is $0,023, and 

 the interest charge per acre averages about $0,007. 



The repair charges on spring-tooth harrows are very small per acre 

 covered, being only $0,011 on the average. The total repairs made 

 during the life of the average spring-tooth harrow cost about 47 per 

 cent as much as the harrow itself when new. 



THE SPIKE-TOOTH HARROW. 



The spike-tooth harrow (Table V) is not in such general use in this 

 section as is the spring-tooth harrow. It is a longer-lived implement 

 than the spring-tooth harrow by about 27 per cent in terms of years, 

 but it does about one- third less work in terms of acres. The class of 

 soils on which the spike-tooth harrow can be used is lighter, and the 

 character of work required of it is much less severe. In this section 

 the spike- tooth harrow lasts an average of 14 years, doing 43 days 

 of work and covering 676 acres of land. Like the spring-tooth, har- 

 row and walking plow, it is a low-priced implement, so that the 

 interest charge, as well as the machinery or replacement charge per 

 day and per acre, is relatively low. 



Spike-tooth harrows of the average size given in Table V C ost when 

 new about $10.50. The average cost for harrowing an acre is $0,016 

 for replacement and $0,007 for interest. 



Table V. — Spike-tooth harrows — relation of work done annually to service and cost per 

 acre and per day -used on 824 farms. 



Range of area covered annually .... acres . . 



lto20. 



21 to 40. 



41 to 60. 



61 to 100. 



101 and 

 over. 



Average. 





193 

 15.7 

 18.4 

 288.9 

 24 

 6.3 



301 



33.3 



13.6 



452.9 



37 



7.3 



151 



52.8 



12.9 



681.1 



40 



9.5 



138 



86.4 



12.4 



1,071.4 



64 



10.6 



41 



166.6 



10.0 



1, 666. 



79 



13.8 







48.3 

 14.0 





676.2 





43 



Average width of harrow f eet. . 



8.5 





$7.75 

 2.76 

 4.42 



§9.00 

 4.22 

 3.94 



$12. 00 

 3.35 

 5.29 



$13.00 

 7.32 

 5.21 



$17.00 

 7.70 

 5.60 



$10. 50 





4.76 



Total interest during life at 6 per cent , 



4.76 



Total of depreciation, interest, and 



14.93- 



17.16 



20.64 



25.53 



30.30 



20.02 







Cost of spike-tooth harrow: 



$0. 622 

 .052 



$0. 464 

 .038 



$0. 516 

 .030 



$0,400 

 .024 



$0. 383 

 .018 



$0. 465 





.029 







The spike-tooth harrow is an implement having lower repair 

 charges per acre than does the spring-tooth harrow, the average 

 being only $0,007 per acre. It is not subjected to the severe strains 

 met by the spring-tooth harrow, as the latter is used on much heavier 

 and more stony land where the spike-tooth harrow would not work 



