/NFLUENT/AL fPA/NFALL 



- /A/CHES PEP MONTH AVA/LABl-E FOP TPANSP/RAT/ON 



885 1890 1895 1900 1905 1910 1915 1920 1935 1930 1935 1940 1945 1950 



z 



EFFECTIVE 



INCHES 



PER 



EFFECTIVE 



1885 1890 1895 1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 



Figure 2. 

 Influential Rainfall — inches per month available for transpiration — Yudnapinna. 



of May to August inclusive, and particularly in June. The expected occurrence of 

 monthly rainfall exceeding 4S.D ^'^^ (Table 1.) confirms the greater reliability of 

 favourable soil moisture conditions in winter, (Cornish, 1952). The monthly values 

 for influential rain have been summed to give a seasonal value; the mean influential 

 seasonal rainfall for 67 years is 2.85 inches and the mean number of months with 

 effective precipitation is 3.2 months per annum. Years with a seasonal value of less 

 than 2.0 inches of effective rain have been classified as drought seasons, and those 

 with a value greater than 2,0 inches have been classed as seasons favourable for 

 herbage production. 



The amount of growth that can be made on limited quantities of available mois- 

 ture has been assessed in field and glasshouse studies of transpiration in relation to 

 growth. These indicate an average value for Kochia and Atriplex spp. of 3 cwt. dry 

 material per acre inch of water transpired, and this appears to be capable of suppor- 

 ting a sheep on 20 acres, or 32 sheep to the square mile for a period of 12 months. 



MS.D^-'''^ is equivalent to 0.4E°-^5 (Prescott, et al., 1952). 



131 



