Clover as a Preparatory Crop for Wheat. 417 
preceding sample ; it contains a good deal of potash and phos- 
phoric acid, and may be presumed to be well suited to the 
growth of clover. It contains more carbonate of lime, and is 
somewhat lighter than the sample from the part of the field twice 
mown for hay, and may be termed heavy calcareous clay. 
An acre of this land, 18 inches deep, weighed when very 
nearly dry : — ■ 
Surface, G inches 2,407,900 
Next „ 2,444,200 
3rd „ 2,480,500 
Or in round numbers every 6 inches of soil weighed per acre 
2J millions of pounds, which agrees tolerably well with the 
actual weight per acre of the preceding soil. 
The amount of phosphoric acid and nitrogen in each 6-inch 
layer was determined separately as before, when the following 
results were obtained : — 
In Dried SoU. 
1st, 6 inches. 2nd, 6 inches. 3rd, 6 inches. 
Pcrceutcage of pliosphoric acid .. '159 .... "166 .... '140 
Phosphoric acid -189 .... -134 .... '089 
Equal to ammonia -229 .... '162 .... -108 
An acre, according to these determinations, contains in the 
three separate sections : — 
1st, 6 inches. 2nd, 6 inches. 3rd, 6 inches, 
lbs. lbs. lbs. 
Phosphoric acid 3975 .... 4150 .... 3500 
Nitros;en 4725 .... 3350 .... 2225 
Equai to ammonia 5725 .... 4050 .... 2700 
Here again, as might naturally be expected, the proportion of 
nitrogen is largest in the surface where all the decaying leaves 
dropped during the growth of the clover for seed are found, and 
wherein root-fibres are more abundant than in the lower strata. 
The first 6 inches of soil, it will be seen, contained in round 
numbers 2^ tons of nitrogen per acre, that is, considerably more 
than was found in the same section of the soil where the clover 
was mown twice for hay ; showing plainly that during the ripen- 
ing of the clover-seed the surface is much enriched by the nitro- 
genous matter in the dropping leaves of the clover-plant. 
Clover-roots. — The roots from 1 square foot of this soil, freed 
as much as possible from adhering soil, were dried at 212°, and 
when weighed and reduced to a fine powder, gave on analysis 
the following results : — 
*Organic matter 64-76 
fMineral matter 35-24 
100-00 
* Containing nitrogen 1-702 
Equal to ammonia 2 '066 
t Including clay and sand (insoluble siliceous matter) 26-04 
