Experimental Crops at Rothamsted. 
127 
Rothamsted, with the records of the conditions of heat and 
moisture under which the crops have been grown, brings clearly 
to view — namely, that, as compared with the hay crop, the corn 
crops arc not only less dependent on the amounts of rain falling 
during the period of active vegetation, but more on a relatively 
high degree of temperature during that period. This is more 
strikingly the case when wheat is grown by means of readily 
soluble mineral and nitrogenous manures, than when it is grown 
■without manure, or with farmyard manure. Without manure 
the produce is comparatively more dependent on the amount of 
certain constituents brought down by the rain, or rendered 
available by its means from the stores of the soil itself; and it 
would seem that where farmyard manure is employed, a con- 
siderable amount of rain is required during the early growing 
period to aid its decomposition, and so to set free, distribute, and 
render available, its fertilising constituents. In the case of the 
artificial manures, on the other hand, some of the most active 
fertilising constituents are supplied in a much more soluble form, 
and require a less amount and continuity of rain for their solu- 
tion and distribution throughout the pores of the soil within a 
given range. 
It is seen, then, that several reasons concur to render corn 
crops less dependent on the fluctuations in the amount of rain 
falling during the period of active vegetation and accumulation 
of substance than is the hay crop growing under otherwise 
parallel conditions as to soil and manure. It is quite intelligible, 
too, that the autumn-sown wheat, with its much longer time for 
the formation and distribution of root, and its tendency to 
develop proportionally more in the lower and proportionally 
less in the upper layers of the soil, than the spring-sown barley, 
should be less adversely affected than the latter by a deficiency 
of rain during the period of active above-ground growth. 
Table XII. brings together at one view the percentage amounts 
of water retained by the soils and subsoils of the different fields, 
under the various conditions as to season, cropping, &c. The 
results so summarised relate to samples collected as under : — 
1. From the experimental wheat field, just before harvest, 
1868 ; mean of three plots differently manured. 
2. From the experimental wheat field, in January, 1869, when 
the land was supposed to be saturated ; mean of the same three 
plots differently manured. 
3. From uncropped land, near the end of June, 1870. 
4. From land cropped with barley, closely adjoining the un- 
cropped land ; samples collected at the same date, end of June, 
1870. 
