47 



nitrate of soda by 3.4; and ammonium salts by 2.1. Silicates, 

 although in the absence of phosphate they materially increase the 

 yield, have no apparent effect upon gout fly infestation. 



The data for 1923 were more satisfactory in that the plots 

 this year were homogeneous. The differences in infestation 

 associated with manurial treatment were on the whole similar to 

 those of 1922. Phosphates, potassium, sodium and magnesium 

 salts and rape cake again reduced infestation materially ; silicates 

 were again inoperative, but the small reduction in infestation 

 ascribable in 1922 to nitrogenous mineral manures was absent. 



RAINl-ALL AND WHEAT YIELDS. 



XII. R. A. Fisher. " The Influence of Rainfall on the 

 Yield of Wheat at Rothamsted." Philosophical Trans- 

 actions of the Royal Society of London, B., 1924. Vol. 

 213, pp. 89-142. 



This paper is the report of the methods and results of a 

 large scale statistical reduction of the Rothamsted records of 

 rainfall and wheat yields. The objects of the enquiry were (I) to 

 ascertain the actual effects of varying rainfall as a factor in crop 

 variation ; (II) to discover the differential responses to rainfall of 

 crops grown under different manurial treatments; (III) to lay a 

 foundation both of statistical method and of ascertained fact for 

 the agricultural evaluation of a particular season's weather, as 

 is required for any effective system of agricultural insurance. 



The greater part of the paper is devoted to the solution of 

 mathematical problems, and the development of statistical 

 methods, adequate to handle the type of data which it is required 

 to treat. The procedure which emerges from the solution of these 

 problems consists in making a detailed analysis of the weather 

 sequence in each individual year for which crop records are 

 available, so as to obtain measures of the several meteorological 

 characteristics of each year. The yields are then expressed in 

 terms of these measures in such a way that the average effect 

 of a given weather variation upon the final crop can be calculated 

 for all times of the year. 



This procedure is applied to 65 rainfall sequences, and the 

 average effect at all times of the year of an inch of rainfall is 

 obtained for the 13 plots of Broadbalk wheat field which have 

 been for the whole period under uniform treatment. Plots 

 differently manured show very striking differences in the rainfall 

 response, indicating that the prevailing climate is a considerable 

 factor in determining the suitability of manurial dressings. All 

 plots show that the rainfall of the district is on the average in 

 excess of the requirements of wheat, but several plots indicate 

 that more rain would be advantageous in October. All plots 

 receiving nitrogenous fertilisers, including the 17 and 18 mineral 

 series which receives only residual nitrogen, show a considerable 

 loss of yield due to rain in January, which is apparently due to 

 the loss of nitrates in drainage water. Those plots in which 

 nitrogen deficiency is of rarest occurrence^ such as the dunged 



