232 The Book of the Rothamsted Experiments. 
wholly in developing its system of roots. Should the weather 
be wet and the soil in a saturated condition the root system 
will be restricted, both because of the deficient aeration and 
because the roots need not extend far in order to obtain the 
water necessary for growth.” A wet winter is therefore almost 
invariably followed by a poor wheat crop at harvest. This is 
fully borne out by the Rothamsted yields, for a comparison 
between the average wheat crop following the ten wettest and 
the ten driest winters shows that with a November to February 
rainfall of 13*01 in. the wheat yield was 26*2 bushels per acre, 
whereas with a rainfall of 5*79 in. the yield was 34*9 bushels 
per acre. The same effects have been recently demonstrated 
statistically from meteorological observations by Dr. Shaw. 1 
Scientific facts like these enable the observant farmer to fore- 
cast to some extent the result of his work and to provide 
accordingly. 
The barley experiments began in 1852. On the land 
continuously cropped the decline in production on the un- 
manured plots has been much more marked than on the wheat 
plot similarly treated, indicating a progressive decline in fertility 
without reaching a point, as in the case of the wheat crop, 
where a constant yield is annually obtained. This is attributed 
to the more limited root range of the barley plant, though there 
is also evidence of a run of less favourable seasons than in the 
case of wheat. The effect of nitrogenous and mineral manures 
upon this crop is discussed and illustrated graphically. The 
experiments bring out the great importance to the barley crop 
of phosphoric acid ; and the practical deduction is that 3 cwt. 
of superphosphate per acre may be profitably used on most 
soils. Even with barley after roots superphosphate is valuable, 
hastening the ripening and making the sample more uniform. 
At the same time the crop requires a fair amount of nitrogen, 
as without it the yield will be low and the berry small. Excess 
of nitrogen, however, results in “ coarseness and an excessive 
proportion of nitrogen in the grain, deteriorating the quality.” 
Passing over the oat experiments which lasted from 1869 to 
1878 and were abandoned because the land became unworkable 
through excessive wet, we come to the experiments upon root 
crops — mangels, turnips, potatoes, and sugar beet. It will be 
a sufficient indication of the importance of the experiments 
with mangels to state that these show the effects of nitrogenous 
and mineral manures ; the value of farmyard manure ; the 
proportion of root to leaf ; and the composition of the roots as 
affected by the manures applied. The experiments prove 
the great value of farmyard manure, which forms the best 
1 Journal of the Royal Statistical Society, Vol. LXV1II., Part II., 1905, 
pp. 285-287. 
