818 EXPERIMENT STATION RECORD, 



a correctiA'e foi* acidity, the quest of nitrogen, tlie release of soil nitrogen, nitri- 

 fication, reclaiming lost nitrogen, soil inoculation, draining tlie land, soil water — 

 how it is lost and how it may be held, dry farming — a problem in water con- 

 servation, tillage tools, the cultivation of crops — the tools and purpose, stable 

 manure — its composition and its preservation, handling manure on the farm, 

 buying plant food for the soil, using chemical manure intelligently, mixing 

 fertilizers at home, dairying — an example in soil building, rotation of crops, 

 and the old worn-out soils — what we may do for them. 



Chem^ical analysis of soils, W. P. Brooks (Elassachusetts Sta. Circ. 11, pp. 

 2). — This is a brief statement regarding the probable value of soil analyses as 

 means of determining fertilizer requirements and of the conditions under which 

 the station will undertake such analyses for private parties. 



Moisture content and physical condition of soils, F. K. Cameron and F. E. 

 Gallagher (U. (S'. Dept. Agr., Bur. tioils Bui. 50, pp. 70, figs. 33). — This bulletin 

 gives the results of an investigation on the relation of physical condition tu 

 moisture content. 



In these investigations the soils were put into different states with varying 

 amounts of water and then subjected to various quantitative physical tests. 

 Account was also taken of the judgment of experienced greenhouse men as to 

 the general i)hysical condition of the soils before and after the measurements 

 were made. The physical factors studied were penetration and cohesion, ap- 

 parent specific gravity or volume as related to moisture content and successive 

 wetting and drying, rate of evaporation, and moisture distribution. The previ- 

 ous investigations on each of these phases of the subject are reviewed and the 

 sjjecial apparatus and methods employed in the investigations here reported are 

 described in detail. 



The conclusions in general are that the physical condition of the soil is most 

 intimately connected with its Avater content, as shown not only by the general 

 behavior and ai)pearance of the soil but also by the systematic quantitative 

 measurements of the physical factors named. The investigations are further 

 held to show a marked accentuation in the physical properties at a critical 

 water content and that this critical content is identical with the optimum v^^ater 

 content. This critical moisture content was found to agree quite closely with 

 the moisture equivalent as detei'mined in 8 soils by the Briggs and McLane 

 method (E. S. R., 11), p. 416). 



" The moisture-penetration curve shows a minimum force required for pene- 

 tration at the oi)timum water content; the moisture-apparent specific gravity 

 curve shows a minimum i)oint at the optimum water content: the curves 

 for evaporation show a marked difference in the rate of evaporation above 

 and below the optinunn water content. It is apparent, therefore, tliat the 

 true significance of oi)timum water content is that particular content at 

 which the soil can be put into the best possible condition for plant growth. 

 The plant can then best draw its needed water from the soil because all 

 the other factors making for good growth are also at their best. Moreover, 

 an increase in water content in excess of the optimum generally produces a 

 greater detrimental effect on the plant than a decrease below the optimum." 



The conclusion is therefore drawn tliat as a rule the physical optimum as 

 determined by the soil properties is also the physiological optimum as deter- 

 mined l)y the plant. "The available evidence seems to be conclusive that the 

 l)roblem of water supply and optimum water content is fundamentally a soil 

 problem and incidentally a plant problem." The data reported in support of this 

 conclusion regarding the physiological optimum include deterrpinations accord- 

 ing to Heinrich's method (E. S. R., 7, p. 481) of the moisture content at which 1!) 

 different kinds of plants began to wilt in a calcareous soil and in a peaty soil. 



