44 
INVESTIGATIONS ON ROTHAMSTKD SOILS. 
sodium and magnesium salts), with only 4-3 pounds of nitrogen as 
ammonium salts. This crop has given more produce than that receiv- 
ing twice the quantity of ammonium salts without minerals, viz, 
3,842 pounds. Its nitrogen is over 0.11 per cent (with carbon about 
1.02 per cent). 
Then follows a series of plats all getting 86 pounds of nitrogen as 
ammonium salts (or sodium nitrate), and all well supplied witli phos- 
phates, with or without additions of alkaline salts. Plat 11 gets, 
with 80 pounds of nitrogen as ammonium salts, phosphates only. It 
shows 146 pounds more of annual. produce per acre than plat 6, the 
next above it, and the nitrogen is increased to 0.113 per cent (with 
carbon nearly 1.11 per cent). Plat 16 now receives 86 pounds only of 
nitrogen as sodium nitrate, with full minerals. Its average yield, 
however, is low, because this average includes nineteen years in which 
the plat was not manured. Previously to this period it was heavily 
dressed with ammonium salts, and in 1865 was the richest in nitrogen 
among the chemically manured plats; but during the long interval 
between 1865 and the next sampling in 1881, its nitrogen became again 
reduced nearly to the level of that of plat 3. Since 1884, however, it 
has received nearly 5 hundredweight of nitrate of soda, containing 
86 pounds of nitrogen, per annum; and, after ten years of this treat- 
ment, we find that, in 1893, although it does not take quite the lead- 
ing place, it resumes its rank among the plats comparatively rich in 
nitrogen, for the nitrogen has risen to nearly 0.118 per cent (the car- 
bon being 1.06 per cent). Notwithstanding the period of starvation, 
the average annual produce all through has been 4,824 pounds, or 836 
pounds higher than that of plat 11, which has been continuously sup- 
plied with ammonium salts and phosphates. This difference has, no 
doubt, been due largely to the full supply of minerals, for it has 
received a full supply of alkaline salts as well as of phosphates. 
Next comes a series of seven plats averaging about 5,600 pounds of 
annual produce, and averaging rather more than 0.12 per cent of 
nil pogeu (with carbon over 1.14 per cent). In this series the percen- 
tages of nitrogen are not all in the order of the crop produce. But, in 
the whole of the sixteen plats in our list, only four break the sequence 
to which 1 have already alluded, viz, that the greater the annual 
yield of crops, the greater is the percentage of nitrogen found in the 
surface soil. The plats which individually break this rule or sequence 
are plats L3, 7, i)a, and 8. These plats have all given large yields, 
mainly owing to the influence of potassium salts. They have yielded 
in their crops a considerably larger quantity of nitrogen than any of 
the others; but they do not show more nitrogen in the surface soil. 
One is tempted to ask whether the crops well supplied with phos- 
phates and nitrogen have, under the influence of potassium salts (with, 
in many cases, sodium and magnesium salts as well), had less difficulty 
in feeding themselves than those of the plats Prom which potassium 
