THE HKiiADHALK WHEAT SOILS. 
Ill 
the very highly phosphated plats on the other, though the descent by 
drainage may <>f course have become greater in later years, as phos- 
phates have accumulated. 
Unfortunately, Dr. Voeleker made no determinations of the phos- 
phoric acid existing in the drainage water from the dunged plat 2b. As 
lias been menl ioncd elsewhere, t he absorpt i ve character of the soil of 
this plat is such that it is very retentive of moisture, and the drain- 
pipes very seldom run except in very wet weather, and Dr. Voeleker 
was unable to obtain samples of the drainage water from this plat 
when the oiher samples were collected. 
( t KN 1 . liA I . ( 'ONCLCSIONS AS T<> PlIospUoRIC ACID. 
The genera] conclusions derived from the phosphoric-acid results, 
as summed up in the paper recently laid before the Royal Society, 1 
arc to i he effect that by far t he greater proportioE of t he unconsumed 
phosphoric acid in the manure i> accumulated in the surface soil, 
although for the most part originally Soluble in water. In the case 
of dung there is a considerable descent into the second and third 
depths of '.» inches, and there is also evidence Of considerable descent 
into 1 he second and even into the third depths in t hose cases in which 
superphosphate lias been accompanied by constant dressings of potas- 
sium sodium, and magnesium salts. The greater part of the calcu- 
lated accumulation, however, is found by analysis in t he surface soil, 
and a large proportion Of it is found in a condition in which it dis- 
solves in a weak solution of citric acid. 
While the differences between the total percentages of phosphoric 
acid in the surface soil correspond fairly with the history of the plats, 
they would not suffice, in the absence of a knowledge of such history, 
to give any adequate indication of the profound differences in phos- 
bhatic condition which we know to exist . I Jut the relative proport ions 
of cit ric-acid-soluble phosphoric acid appear to afford a striking index 
to the relative phosphatic fertility of the soils. In the case of the 
subsoil samples the irregularities and variations in the natural or 
Original phosphoric acid of the subsoils themselves are such that the 
total percentages tell us, as a rule, nothing, while the citric-acid 
results frequently show striking and consistent differences, and are 
also of considerable interest in connection with the problems of root 
range and subsoil feeding. 
The influence of akaline salts on the retention of phosphoric acid 
in a less fixed and presumably more available condition is interest- 
ing, corresponding as it does with the increase of saline applications. 
The superabundance of phosphoric acid estimated to have been 
supplied in dung oxer fifty years is less satisfactorily accounted for 
than is the case with the phosphoric acid in the chemically manured 
1 Philosophical Transactions of the Royal Society [England], 1901, series B, vol. 
194, pp. 235-290. 
