KOLJRXH DAY. 



MONDAY MORNING SESSION. 



The a>s(M-iatioji convened at 9 o'clock for the reading of special 

 papers in accordance with the resolution adopted in 1907. Mr. 

 Toll nan, as chairman of Section C, presided. 



METHODS RELATING TO THE RATE OF DECOMPOSITION 

 OF ORGANIC MATTER IN THE SOIL. 



By JACOB G. LIPMAN. 



< 'hemi- -ally con-ideretl, humus is a comparatively inert substance; biologically con- 

 -idere.l. n i0 readily Buaceptible to a wide range of modification. The host of bacteria, 

 fun-i. aii-1 yeasta that inhabit it find no difficulty in inducing its transformation, which, 

 in t urn, reacts mi the growth <if crops. In so far as the bacteria and other microorgan- 

 i-m~ 'i ih- - il titnl suitable conditions of moisture, temperature, aeration, and chem- 

 ical -Mil.-! inn ii in, tin- humus will decay rapidly. In so far as these conditions are 

 unsuitable, the decomposition will he slow; and the supply of available nitrogen, and 

 prohahh >i' phosphorus and potassium also, will be but meager. This fact was well 

 appreciated even bef,,r- the function of bacteria in the soil was recognized, as may be 

 seen, for instance, from some experiments by Boussingault and Loewy published in 



Tin- recognition of humus OH an important factor in crop production & has led logically 

 to tin- analytical study of its decomjxwition products and their quantitative deter- 

 minatioii. Carbon dioxid. anunonia, and nitrates seemed important among these de- 

 < <mi{>ositio!i products not merely because of their indirect or direct action as sources of 

 plant I'M id. but because of their value as indicatorsof quantitative reactions. Students 

 :1- tried t" establish a possible relation between the productive power of soils and 

 their content <>f carbon dioxid, ammonia, or nitrates. We need only mention here in 

 passing the investigations ..f Iloiissingault and Loewy,c and of von Fodor,<i as bearing 

 on the pr. .irbon dioxid in soil air; the rather careful work of Baumann f on 



the determination ami presence of ammonia in soils; and the examination by Bous- 

 singault ' of various soils for their content of nitrates. 



oMemoire sur la Composition do 1'Air Confine dans la Terre Vegetale, Ann. chimie 

 physique. 1853 (3), 50:3. 



tebig, I Me < 'hemie iii ihrer Anwendung auf Agricultur und Physiologic, 9th ed., 

 Kraunschwei-. |s7ii, p. _;. 



cLoc. cit. 



<l Deutsche Vierteljahrschrift offentl. Gesundheitspflege, 1875, 7:205-237. 



' Ueber die Bestimmung des im Boden enthaltenen Ammoniak-Stickstoffes und 

 iiber die Menge des assimilierbaren Stickstoffes im unbearbeiteten Boden, Habilita- 

 tions-Schrift. Berlin, 1886. 



/ Agronomic, chimie agricole et physiologic, 3d ed., 2 :40. 



(191) 



