Summary 



Perennial shrub species of Atriplex and Kochia originally dominated the arid 

 pastoral areas of southern Australia with a mean annual rainfall of less than 10 

 inches. 



These pastures have been stocked with sheep for approximately a century ; 

 over- grazing, leading to denudation, has been marked. Some undamaged associa- 

 tions of shrubs remain, and some regeneration has occurred, but for the most part re- 

 covery of the pastures has been limited. 



On both relatively undamaged and degraded country there is scope for improved 

 methods of utilization. A study of grazing management within the North- west Pas- 

 toral District of South Australia conducted over a period of 11 years is described. 



The climatic factors, and in particular, the rainfall characteristics of the area, 

 have been analysed in the short and the longer term; and these have been related to 

 the reaction to grazing of Kochia sedifolia and to major trends in the sheep popula- 

 tion. 



Marked improvement in the density and vigour of Kochia sedifolia resulted from 

 intensive stocking during favourable seasons. The reaction of this shrub to grazing 

 is explained in terms of an increased circulation of nutrients from the vegetation to 

 the soil via the grazing animal, and thence back to the plant. A reduction of com- 

 peting herbage, and more effective use of soil moisture by the shrub, as a conse- 

 quence of its pruning by sheep, are contributing factors. 



The general application of the principles discussed in the paper may lead to 

 more effective utilization of the pastures associated with arid and semi- arid regions. 



References 



Cornish, E.A. 1952. Personal communication. 



Crocker, R.L., and Skewes, H.R. 1941. Trans. Roy. Soc. S. Aust. 65, 44. 



Davidson, J. 1938. Trans. Roy. Soc. S. Aust. 62, 141. 



Jessup, R. W. 1951. Trans. Roy. Soc. S. Aust. 74, 189. 



Osborne, T. G.B., Wood, J.G., and Paltridge, T. B. 1932. Proc. Linn. Soc. N.S.'W. 57, 377. 



Prescott, J. A. 1949. J. Soil Sci. 1, 9. 



Prescott, J. A., Collins, Joyce A., and Shirpurkah, G. R. 1952. Geographical Rev. 61, 118. 



Richardson, A. E.V., Trumble, H. C, and Shapter, R.E. 1932. Coun. Sci. Industr. Res. Aust. 

 Bull. No. 66. 



Sears, P. D., and Goodall, V.C. 1948. N. Zealand ]. Sci. Tech. 30, 231. 



Theron, J.J. 1951. /. Agr. Sci. 41, 239. 



Trumble, H.C. 1952. Adv. Agronomy, 4. Academic Press Inc. New York. (In press) 



Trumble, H.C, and Donald, CM. 1938. Coun. Sci. Industr. Res. Bull. No. 116. 



Woodroffe, K. 1941. J. Aust. Inst. Agr. Sci. 7, 117, 



147 



