420 



THE WHEAT PLANT 



In the season of 1878-9, from the 22nd of October to the first week 

 of December, the weather was cold and wet. The five months ending 

 March 31 were cold with much snow and rain, and from April to July 

 the days were cold and wet with little sunshine. Lawes states that it was 

 the worst season experienced in Great Britain since 1816. 



Examination of the annual yields shows that even on the exhausted 

 plot which has carried wheat for sixty years without manure the impress 

 of a favourable season is very marked by a distinct increment, which in 

 1863 amounted to more than 4 bushels per acre. Perhaps more remark- 

 able is the fact that in the best season, plot 7 gave 53 bushels per acre, 

 while the application of the same amount of manure to this plot in 1879 

 resulted in the production of only 16 bushels. 



Thus it is evident that season is of far greater import than any other 

 factor in determining yield : cultivation and manuring are of little avail 

 when the climatic conditions are unfavourable. 



So far as this country is concerned the average annual temperature is 

 usually too low for the best development of the wheat plant, but reduced 

 yields of the grain are attributable to the high rainfall rather than to the 

 low temperature. 



The relation between the average yields in England during the twenty- 

 one successive years 1884-1904, and the total rainfall for the three 

 autumnal months, October, November, and December, was investigated 

 by Shaw, who found that a close approximation to the actual returns at 

 harvest is given by the formula : 



Yield per acre =39-5 bushels-;; of the rainfall (expressed in inches) 

 of the previous autumn. In years of high yield the autumnal rainfall is 

 considerably below the average, in bad seasons it is excessive. 



The importance of rainfall is seen in the following Rothamsted returns : 



Soil. Although wheat will grow upon almost all kinds of soil from 

 the heaviest clays to the sands and gravels, the highest yields are only 

 obtained upon rich, deep, well-drained loamy clays, the physical character 

 of which is fairly uniform down to a depth of 2 or 3 feet. 



Upon clays, especially if imperfectly drained, the yields are con- 

 stantly smaller, as they are also upon the light sands, gravels, and peaty 



