EFFECT OF MOISTURE CONTENT OF A SANDY SOIL ON 
ITS NITROGEN FIXING POWER 
Cr -. LirPwaAN AND -L: To SHARP 
Since attention to the well being of the beneficial soil bacteria 
is admittedly a vital factor in the maintenance of soil fertility, it 
becomes as important a question to determine the relation of a 
soil’s moisture content to its bacterial activity as to ascertain the 
relation thereof to the growth of the plant itself. Relatively little 
work has thus far been carried out along such lines, and such data 
as we have bear, so far as we are aware, almost wholly on the rela- 
tion of the soil’s water content to ammonification, nitrification, 
and dentrification. Nothing but the one investigation below 
named, which is possessed of any cogency, has thus far come to 
our notice which deals with the aspects of the same question with 
regard to nitrogen fixation. The writers therefore present in this 
paper a series of interesting results bearing on the subject in ques- 
tion which were obtained in the course of some of their studies on 
the natural nitrogen fixing flora of soils. 
The history of the general subject of the relation of soil mois- 
ture content to bacterial activity, as above intimated, records but 
few investigations. Those possessed of any cogency here are those 
of ENGBERDING,’ Lipman and Brown,? CoLEMAN,} DEHERAIN,* 
and Krainsky.s The first named investigator found that the 
number of bacteria increased with the water content of the soil 
until the latter reached 80 per cent of saturation, and that it de- 
creased when moisture was supplied in greater quantities. LIPMAN 
and Brown found in a neglected clay loam soil that ammonifi- 
cation increased with the increase in water content even up (0 
* Cited from Exp. Sta. Record 21: 1909, p. 620. 
?.N.J. Exp. Sta. Rpt. 1908, p. 105. 
3 Cent. Bakt. 207: 1907-1908, pp. 401 and 484. 
4 Compt. Rend. 125§:1897, p. 282. 
’ Cent. Bakt. 207: 1907-1908, p. 732. 
_Botanical Gazette, vol. 59] [402 © 
