94 Drought of 1870 and 
assume, however, for the purpose of illustration, that in the 
growth of hay, as in that of the grain-crops, about 300 parts of 
water will be exhaled for 1 part of dry substance assimilated ; 
and since one of the experimental plots of meadow land at 
Rothamsted has given an average, over fifteen years, of 3 tons of 
hay, or about 2^ tons of dry substance per acre per annum, its 
growth would again represent an exhalation of about 750 tons of 
water per acre per annum — but extending in this case not later 
than to the middle or end of June. 
We will now adduce some special cases illustrating the 
amount of water exhaled by different crops, and their dependence 
on the rainfall of the period of active growth, or on the supplies 
of moisture previously accumulated within the soil. 
Results kelating to the Growth of the Hay-crop. 
The following Table (I.) shows the amount of hay obtained 
per acre each year for fifteen years in succession (1856-1870) : — 
1. Without manure. 
2. With mixed mineral manure and 400 lbs. ammonia-salts 
per acre per annum. 
3. With mixed mineral manure and 550 lbs. nitrate of soda 
per acre per annum (thirteen years only, 1858-1870). 
The Table also shows, side by side with the records of produce, 
the amount of rain, in inches, which fell at Rothamsted each year 
Table I. 
Years. 
Hay pee Acue. 
Without 
Manure. 
Mineral 
Manure and 
Ammonia- 
salts. 
Mineral 
Manure and 
Nitrate of 
Soda. 
Mean. 
Rain at Rothamsted. 
April. ' May. June. 
Total. 
1856 
1857 
1858 
1859 
1860 
1861 
1862 
1863 
1864 
18G5 
1866 
1867 
1868 
1869 
1870 
Cwts. 
22J 
25| 
22 
*--« 
241 
25i 
27i 
20i 
24 
lU 
23^ 
29i 
171 
38 
Average 22f 
Cwts. 
56f 
57i 
64 
551 
501 
56^ 
57J 
53f 
50i 
341 
441 
48 
59! 
68^ 
291 
52? 
Cwts. 
5U,« 
541 
52g' 
51 
h8\ 
60^ 
471 
58f 
64J 
69 
761 
561 
57i 
Cwts. 
39i 
41^ 
451 
44 
411 
44f 
45J 
44J 
45 
31J 
421 
47i 
48i 
61 
301 
43* 
Inches. 
2-61 
2-16 
58 
70 
94 
28 
84 
2 
2 
1 
1 
2 
0- 96 
1- 25 
0- 47 
1- 95 
2- 82 
2-19 
2-13 
0-46 
Inches. 
1- 04 
2- 91 
1 -01 
1-88 
3- 05 
1-24 
3-35 
0- 73 
3-23 
1- 35 
Indies. 
1- 91 
2- 21 
0- 96 
2-72 
6-26 
2- 98 
3- 41 
4- 60 
1- 79 
0- 68 
4-51 
1 - 06 
0- 37 
1- 07 
0-98 
1-89 2-30 ! 2-37 
Inches. 
9-22 
5- 47 
6- 09 
7- 51 
12-50 
5 • 30 
9-16 
6- 57 
4-92 
4-20 
7- 70 
7-23 
3-29 
6-43 
2-79 
6-56 
