10 Jan., 1916.] Wheat Yield and Winter Rainfall 37 



RELATIONSHIP BETWEEN THE AVERAGE WHEAT 

 YIELD AND THE WINTER RAINFALL. 



Bij A. E. Y. Bichardson, M.xi., B.Sc, Agricultural Superintendent. 



That the Victorian average wheat yield is dependent on the rainfall 

 during the growing period of the crop is a matter of common ohservatiou. 



That there is a definite relationship between the two, and that this 

 relationship may be used to forecast the probable average wheat yield 

 early in November is probably not suspected by the casual observer. 



A comparison of the average wheat yields of Victoria for the past 

 25 years with the composite rainfall over the wheat belt from May 

 to October throughout the same period appears to establish such a 

 relationship. In order to determine the composite winter rainfall of 

 the Victorian wheat belt, ten typical stations were chosen, and the 

 composite average rainfall from these centres expressed in inches of 

 rain was compared with Victoria's yield in bushels per acre. An 

 extraordinary coincidence resulted. During the 25 year period the 

 composite winter rainfall expressed in inches of rain at these centres 

 corresponded almost exactly with Victoria's average yield expressed in 

 bushels per acre. Thus the average rainfall for the period was 9.5 

 inches, and the average yield per acre 9.1 bushels, or for every inch 

 of winter rainfall ap])roximately an average of 1 bushel of wlioat per 

 ijcre was obtained. 



The centres chosen were ten in number, and rejiresented the chief 

 districts in which Avheat is grown. The centres were Mildura, Ultima, 

 and Beulah, representing the Mallee areas; ^SThill, Horsham, and 

 Donald, representing the Wimmera; Shepparton, Echuca, and Bendigo, 

 representing the northern areas; and Rokewood, representing the 

 Western District. 



The Mallee, the Wimmera, and the northern districts produced in 

 normal seasons roughly 30 per cent, each of the wheat yield, Avhilst 

 the western and central districts produced the remaining 10 per cent. 



The composite winter rainfall of these centres may be taken as 

 representative rainfall of tlie cliief wheat-growing areas of the State. 



That wide fluctuations in the rainfall occur Avill be a]i])ar('nt on 

 considering the gra])h, which sunnnarizes the winter rainfall at 

 these ten centres for the ]tast (piarter of a century. The lowest recorded 

 winter rainfall was at Mildura in 1914, when .73 inches of rain fell in 

 six montlis. The highest recorded winter rainfall at these centres was 

 in 1906, at She])parton, when 19.13 inches fell in the six winter months. 



Tlie accompanying gra])li expresses the variations in tlie composite 

 winter rainfall in inclies of rain, and the average yield in bushels per 

 acre for each of tlie past 25 years. A close scrutiny of the grai)h will 

 I'eveiil ;i nuiiibei- of interesting facts. 



Improvement in Victorian Agriculture shown .u:raphically. 



The ontstiiiidiiig realurc of llie gi'iijili is tlie ini])i-ovcnieiit in eiliciiMicv 

 in Vi<'toii;in ulicil growing during the past decade. This is shown 

 not only in the iiii|)i'oved averages reaped jier acre, but more jiarticu- 

 lai'ly ill the nmnher of hiishels per aci-e won from each in<'h of available 



