AGRICULTURAL UTILIZATION OF ACID LANDS. 5 
TABLE II].—Acidity of green-nanure crops to the acre, in terms of lime require- 
ment per acre. 
Crop. Acidity. | Crop. Acidity. 
OPS Tons. 
ANT Te Tea ets ir ets oe Mann GB Scr Rees | 11B39| RR Che ae a too e Saat A Saee epeeaaae 11 
TRCGRCION ELE es eae oe eae Sas eee OBER TOOMESE Cem emer sree sia en 11 
COM PCA osm se eee seo 8s See ee Se 10 | 
The excessive acidity of these green manures at the time they are 
first plowed under may be more clearly appreciated when one consid- 
ers that the application of 2 to 3 tons of ground limestone per acre 
usually satisfies the requirements of an ordinary acid soil. The 
initial acidity of these green manures is thus shown to be several 
times that of an equal bulk of ordinary acid soil. in the process of 
decomposition, however, green manures, like the leaves already de- 
scribed, tend to pass from an acid to an alkaline state, but at rates 
which have net yet been determined. 
The limé requirement of green manures as given in Table III 
must not be understood as the amount of lime actually required to 
neutralize the acidity of a crop of these plants when plowed under. 
A compact 6-inch layer of green manure would never be used in actual 
practice, but a much smaller amount, as estimated in Table IV. This 
table gives the estimated weight of the dry crop per acre, roots as well 
as tops; the amount of lime in the crop, expressed in terms of ground 
limestone; and the acidity, in terms of the additional amount. of 
ground limestone required to neutralize the initial acidity. 
TABLE [V.— Weight, lime content, and acidity of green manures to the acre. 
Acidity, expressed 
Crop. Weight. Lime content. as lime require- 
ment. 
Tons. Pounds. Pounds. 
PACA leseeme remcmee epee eG Cee | 25 39 267 
IVE CEC LOV.C Tate sett oe meee Sts et er ee a ee 2 131 142 
GOAN; OYE Se Si ee eee era 23 92 200 
POV. =e 2 ok Se Pee eee 2 11 178 
ETO OLMESC LOC Bearers ease fete = a 1 A 89 
INJURIOUS EFFECTS OF ACIDITY. 
Although science can not be said to have demonstrated the full 
details of the various ways in which ordinary crops are injured by 
soil acidity, there is known to be one important chemical process 
which is suspended under acid conditions, namely, the transforma- 
tion of “unavailable” nitrogen into the form of nitrates. The 
nitrifying bacteria do not thrive in acid media. In consequence, 
those crops that require their nitrogen in the form of nitrates suffer 
