390 Experiments with different Top-dressings upon Wlieat. 
ingly accurate results. The proportion of phosphoric acid found 
("12) is but small ; nor does this soil contain much sulphuric acid 
or available alkalies. On the other hand, it is rich in lime and 
clay, and would, no doubt, be much more productive if the field 
were deeper. Being rather shallow, the agricultural capabilities 
of the experimental field are naturally below the average. 
In shallow, stiff, and retentive soils organic matter accumulates 
rapidly. Most of the nitrogen indicated in the above analysis is 
present in' the shape of organic matters : i. e., the roots, leaves, 
and other remains of the preceding crop. A small portion only 
of nitrogen occurs in this soil in the state of ready-formed 
ammonia. 
Before stating the yield of each experimental plot, I shall 
notice briefly the appearance of the crop at different times, and 
give the analysis of the manures employed in the experiments. 
Plot I. — Top-dressed, March 22nd, with Peruvian guano, at 
the rate of 2^ cwts. per acre, cost, 1/. 12s. Gd. per acre. 
On the eighth day after the application of the guano the 
effects of this fertilizer became slightly visible, on the tenth day 
they were a little more marked, and, after a fortnight, plainly 
observable even to a superficial observer. Compared with the 
unmanured wheat, the colour of the wheat on Plot I., though not 
so dark-green as on the portion dressed. with nitrate of soda, was 
deeper, and the plants looked altogether more luxuriant than on 
the unmanured plot. The darker green colour was perceptible 
for more than six weeks, and then gradually disappeared. At 
the same time the wheat-plants grew more vigorously, and at 
harvest time were a good deal higher than the wheat in the 
surrounding field. On analysis the Peruvian guano gave the 
following results :— 
Moisture 17-12 
'Organic matter and ammoniacal salts .. .. 51'31 
Phosphates of lime and magnesia (bone-earth) 22\55 
Alkaline salts 7'94 
Insoluble siliceous matter (sand) 1'08 
100-00 
*Con(aining nitrogen 14-64 
Equal to ammonia 17-77 
These numbers express the composition of a genuine good 
Peruvian guano. 
Plot II. — Top-dressed, March 22nd, with nitrate of soda, at 
the rate of 1| cwt. per acre, cost 1/. 12*. 6d. per acre. 
Already, the fourth day after application, the efifecls of nitrate 
of soda became slightly visible, and in the course of a week the 
