19 
[; 
shortage of labour and fertilisers, but since the end of the war 
there has been an apparent recovery. But until the effects 
of the war are eliminated from the ten-year averages, that is, 
until figures are available for the period 1921-30, it will not be 
possible to compare at all satisfactorily pre-war and post-war 
yields. 
Although this variation in yields is of interest it appears in 
the main to be due to climatic conditions over which the farmer 
has no control. There is no evidence of a general increase in 
the actual productivity of crops nor the reverse, as one would 
hesitate to attribute the declining average yields of recent years 
to any cause other than the weather and to some extent, war 
conditions. In the case of wheat, beans and mangolds, notwith- 
standing the decline in recent years, the general level is still well 
above that of the early years, a condition which does not, 
however, apply to other crops, particularly barley. 
Table 5 in the Appendix gives the average yield per acre of 
the principal crops in ten-year periods since 1885. 
2. Crop yields and extent of cultivation.—In the case of the 
more important crops information as to acreage and total produc- 
bion is, as already explained, collected annually and the results 
are published in the Annual Agricultural Statistics. It is not, 
therefore, proposed in this Report to discuss in any great detail 
the changes that have occurred in those crops, except to draw 
attention to some points of general interest. In the case of 
certain other crops, however, it is possible to give additional 
information obtained in 1925. Table 3 in the Appendix gives 
the acreage under the principal farm crops in England and Wales 
In five-year periods from 1871-75 to 1921-25, and Tables 4 and 5 
the average production and average yield per acre in 10-year 
Periods, 1886-95 to 1916-25, together with the figures for 1925 in 
each cage. 
(a) Corn Crops. 
The two factors contributing to the total production of cereal 
Crops (as indeed of all crops) are the total acreage and the average 
yield per acre. The former, while differing comparatively slightly 
I Successive years, is yet subject to great changes over an extended 
period. On the other hand, the yield per acre shows substantial 
fluctuations in individual years, but over extended periods the 
Averages show less dissimilarity. Neither factor can be said 
to be the only consideration, but the annual fluctuations in total 
Production are caused chiefly (although not entirely ) by changes 
WN yield per acre for which the weather is mainly responsible ; 
while the changes in the average total production over a period 
of 5 or 10 years are due mainly to alterations in acreage, although 
the average yield per acre is also a factor, the importance of 
which varies according to the length of the periods upon which 
the comparison ig based.