1916] FIELD CROPS. 439 



and spring wheat, giving corn stover a value of $3 per ton and sorghum a 

 value of $4 per ton. 



Alfalfa and brome grass proved unsuccessful, and it is stated that for the 

 conditions under which these crops were grown they should have been seeded 

 in rows and cultivated. The average yearly yield of sorghum for seven years 

 was 3.1 tons per acre. As a single crop and also in rotations corn ranked 

 above any of the small grain crops in the profit per acre where the stover 

 and grain are both used. Spring wheat ranked next and gave the most profit 

 when following corn in a rotation. Barley gave less profit than spring wheat 

 and oats wei-e usually grown at a loss. 



Carrying capacity of grazing ranges in southern Arizona, E. O. Wooton 

 {U. S. Dept. Agr. Bui. 367 (1916), pp. 1^0, pis. 10, figs. 5).— The plans and 

 methods of the studies here reported, as well as earlier results secured in 

 the work, have been previously noted (E. S. R., 23, p. 136). This bulletin 

 summarizes the results thus far obtained including those reported in preceding 

 publications. 



Regarding the rate of recovery of the ranges it is stated that three years 

 of complete protection gave about three-fourths of complete recovery for the 

 area where crowfoot grama was the dominant grass at levels of about 3,500 

 to 4,000 ft. with an annual rainfall of from 15 to 18 in. An inclosed pasture 

 of this type of 794 acres stocked with horses and burros at the average rate 

 of 11 head per section recovered somewhat more slowly than the completely 

 protected area beside it, and at the same level, but after 11 years of protec- 

 tion it was not and had not been for two or three years appreciably different 

 in carrying capacity from the completely protected area. Three other areas 

 of 1,065, 1,695, and 1,889 acres, pastured judiciously with approximately all 

 the cattle they could carry, are reported as showing a better productivity 

 than adjacent unprotected grazing land of the same character, and are believed 

 to have materially increased the carrying capacity under the treatment within 

 a period of 11 years. With complete protection the better part of this range 

 recovered rapidly during the first two or three years and approached com- 

 plete recovery in 10 or 12 years. Heavy stocking with cattle did not prevent 

 but retarded recovery, so that after 11 years the grazed areas were but partially 

 recovered though their carrying capacity had increased at least 30 per cent in 

 that time. 



The results of reseeding operations to introduce new species of forage plants 

 or to increase the relative abundance of particular endemic species beyond 

 their natural importance were practically all negative. Scattering the seeds 

 of the best grasses of a region on the denuded areas is recommended wherever 

 the seeds can be had in any quantity at relatively small expense. 



Records were made for a series of years to work out an expression repre- 

 senting the average carrying capacity of the whole range reserve. From 

 weights of the dry material collected for nine years on small measured repre- 

 sentative areas, the total productivity in povinds of forage per acre was cal- 

 culated. The yearly averages indicated the rate of improvement, and the 

 average of all records showed an average total annual production of about 

 1,160 lbs. per acre. The average amount of hay obtained, as based on records 

 covering five years on a total area of 492.5 acres, was 640 lbs. per acre. Three 

 areas of about one acre each cut four years in succession lost in productivity 

 from one-half to three-fourths of what they produced the first year. From 

 the measurements of the small areas the approximate productivity of different 

 forage plant associations was obtained, and from these figures and the areas 

 of each association, the average production of the whole reserve was calculated 

 61574°— No. 5—16 4 



