12 FARMERS ' BULLETIN 826. 



to gravelly loam soil of sufficient depth to permit the use of a mat- 

 tock in grubbing. The cost per acre for eradication on these plots 

 varies in the main with the number of larkspur plants per acre, 

 though not in direct proportion. The work on these first plots 

 was experimental, and the primary object was effective eradication 

 rather than securing a knowledge of comparative costs. Conse- 

 quently, the rate of w r ork was not necessarily the same. The com- 

 parison, however, serves to emphasize the fact that in estimating 

 the cost of any piece of eradication work, the number of plants per 

 acre must be taken into account. 



Plot 4 is in a park area, on a moist, rocky, gravelly loam soil. It 

 was hardly possible to stick a pick into the ground without striking 

 rock. The estimated cost for grubbing is approximately 2J times 

 greater per plant under such conditions than on the deep, sandy 

 to gravelly loam soils of Plots 1, 2, 3 and 3 A. Figured per acre, 

 however, the cost becomes considerably less, for usually there is a 

 much smaller number of plants per acre on rocky soils than on the 

 better sites. 



Plots 2A and 5 are located in willows. On Plot 2A it was neces- 

 sary to cut out about half of the willows, roots and all, before the 

 larkspur could be effectively grubbed. The willows on Plot 5 were 

 dense but straight; consequently, less willow cutting was necessary 

 than on Plot 2A. The cost of eradication in the willows is approxi- 

 mate!^ double the cost per plant on the open areas having a sandy 

 to gravelly loam soil, and approximately one-fifth less than eradi- 

 cation on rocky soil, such as Plot 4. The extra cost for chopping 

 out willows is almost offset, however, by the smaller number of 

 larkspur plants per acre, usually about one-third less than on good 

 soils in the open ; by the character of the soil, usually of a fine tex- 

 ture free from rocks; and by the comparative shallowness of the 

 larkspur roots. 



The costs given in Table 3 are considerably above the average 

 for extensive eradication where experimental data, involving counts 

 of plants and care in following plot lines, are not collected. Fur- 

 ther, experimental plots were selected as more difficult than the 

 average. 



In eradicating the 68 acres of larkspur from the entire range sur- 

 rounding the special plots, the average cost of grubbing in the open 

 was $9.81 per acre, and in willows $10.26 per acre, with a general 

 average of $10.10 per acre. The 68 acres contained approximately 

 one-third less larkspur plants than the experimental plots. 



The cost of extensive grubbing on other National Forests was less 

 than that for the w r ork on the Stanislaus, as shown by Table 4. 

 The work was also slightly less effective. 



