1918] SOILS FERTILIZEKS. 21 



a lime requirement equivalent to 10,814 lbs. of calcium carbonate and nitric 

 nitrogen equivalent to 21.46 parts per million. Three of the plats showed the 

 existence of an acid subsoil to a depth of 3 ft. and nitric nitrogen was found 

 at this depth on each of the plats. Leaching the acid soils with water and with 

 alcohol did not decrease the lime requirement. 



In soil treated with ammonium sulphate at the rate of 10 tons per acre, the 

 nitric nitrogen remained fairly constant, but the lime requirement greatly in- 

 creased. It is suggested that in this case ammonium sulphate remained as such 

 in the soil and reacted with limewater as follows; 



(NH4)2S04+Ca(OH),=CaS04+2Na+2H,0 



Soils stored in closed jars for two years showed no change in lime requirement. 



Nitrification was observed in a soil having a lime requirement equivalent to 

 6,000 lbs. of calcium carbonate, under different treatments as follows : Without 

 lime, check soil 15.78 parts per million, ammonium sulphate 11.5, dried blood 

 24.72, and cottonseed meal 23.23 ; and with lime, check soil 43.54, ammonium 

 sulphate 64.4, dried blood 85.8, and cottonseed meal 66.01. When applied at 

 rates supplying the same amount of nitrogen the following increased lime re- 

 quirement was noted : Ammonium sulphate 2,008, dried blood 610, and cottonseed 

 meal 305 lbs. calcium carbonate. These results confirm the field observation 

 that nitrification is possible on a very acid soil. 



In all the soils studied of which the lime requirement was greater than 3,600 

 lbs. calcium carbonate, more so-called "free" humus (soluble in 4 per cent 

 ammonia) was recovered than "total." "The alkali-soluble humus in a soil 

 of high lime requirement is largely in an uncombined state and represents a 

 condition similar to that brought about by washing a soil with a dilute mineral 

 acid whereby the combined basic material is removed. In a soil well supplied 

 with basic material tJae humus is in a combination insoluble in dilute ammonia. 

 About 25 per cent of the humus extracted with ammonia is precipitated with 

 hydrochloric acid." 



The influence of fineness of division of pulverized limestone on crop yield 

 as well as the chemical and bacteriological factors in soil fertility, N. 

 KoPELOFF {Soil Sci., 4 (1917), No. 1, pp. 19-69, figs. 5). — Experiments conducted 

 at Rutgers College are reported on the influence of fineness of division of 

 pulverized limestone upon crop yields on Carrington silt loam, Wooster silt 

 loam, Cumberland silt loam, Norfolk sandy loam, Sierra sandy loam, and Ports- 

 mouth acid muck. 



It was found that " an increase in flneness of division of pulverized lime- 

 stone from 20 to 40, 60 to 80, 100 to 200, to finer than 200-mesh is responsible 

 for a proportional increase in the yield and total nitrogen content of crimson 

 clover . . , and a corresponding decrease in lime requirement. From the above 

 standpoint there was little choice between burnt lime and 200-mesh limestone. 



" Employing an apparatus devised for measuring the rate of neutralization 

 of soU acidity by different grades of pulverized limestone, it was found that 

 in three different soils the limestone finer than 60-mesh required about three 

 weeks, while 20-mesh limestone required more than seven weeks to effect 

 neutralization. An increase in the quantity of limestone required for neu- 

 tralization was proportional to an increase in fineness of division of pulverized 

 limestone for any given period of time. An increase in fineness of division of 

 pulverized limestone is responsible for an increase in the activity of the bacterio- 

 logical processes of ammonification, nitrification, and nitrogen fixation (within 

 certain limitations) as measured in soil and solution. This holds true regardless 

 of whether the amount of limestone applied is less or somewhat more than the 

 37450'— 18 3 



