620 EXPERIMENT STATION RECORD. 



per gram. The amoebai do not ordinarily occur in numbers nearly as great as 

 do the flagellates. Certain forms of the soil protozoa are active under normal, 

 and oven subnormal, conditions of moisture. The active protozoan inhabitants 

 of most soils are probably restricted to the flagellates. C. cucuUus is ijrobably 

 active whenever the moisture content is much above normal, but does not appear 

 to be so ordinarily." 



Methods of soil sterilization for plant beds and greenhouses, A. D. Selby 

 and J. G. Humbert (Ohio Sta. Circ. 151 {1915), pp. 65-7/f, figs. 2).— This circu- 

 lar describes the jierforated pipe and inverted pan methods of steam steriliza- 

 tion and the formalin method of sterilization for plant beds and greenhouse 

 soils, gives cost data for the different methods, and notes reports on practice in 

 sterilizing soils. The estimate of costs of oi>eration by the different methods is 

 $15.40, $12.20, and $21, respectively, to treat a house 3,000 sq. ft. in area. 



As regards soil sterilization, it is stated that " in general, a sandy soil will 

 require less time to be thoroughly heated to the desired depth than will a silt- 

 loam soil or one of heavier clay. ... A dry soil, and particularly one contain- 

 ing a high percentage of humus, will be very apt to suffer some injury, especially 

 in that portion next to the steam pipes. Light soils, and those rich in humu.s, 

 would better be steam treated with the iian method. ... In practice soil should 

 be wetted to the extent of a little less than good growing conditions when steamed 

 either by pipes or by the pan method ; this condition will generally be found 

 satisfactory in using the formaldehyde drench. . . . Great caution must be 

 observed that a recently steamed soil is not overwatered, thus giving it the 

 water-logged structure which prohibits or greatly retards growth of plants. 

 . . . Beds treated with formaldehye (3 pints to 50 gal. of water or stronger) 

 should be stirred every few days to rid the soil of fumes poisonous to young 

 plants, and such beds should not be seeded or planted for a period of ten days 

 after the drench is applied." 



The present position of the science of manuring- in Germany, ;M. Hoffmann 

 {Internat. Inst. Agr. [Rome^, Mo. Bui. Agr. Intel, and Plant Diseases, 5 (1914), 

 No. 8, pp. 976-984)- — It is stated that while "the weightiest problem of the 

 science of manuring, namely, how to find out, rapidly and surely, the manurial 

 requirements of a given iiiece of land before a crop is put into it," has not yet 

 been solved, considerable progress in this direction has been made possible by 

 the work of Konig on the treatment of soil by steam under pressure, by 

 Mitscherlich on the use of solutions of carbon dioxid, and by Gerlach on the 

 use of 2 per cent citric acid as means of determining the available plant food 

 of soil, and by the work of Wagner and Pfeiffer on plant analysis. It is stated 

 that AVagner's conclusion that meadows, the air-dried hay of which contains 

 less than 2 per cent of potash, 0.7 per cent of phosphoric acid, and 1 per cent 

 of lime, need applications of these substances has been repeatedly confirmed, 

 and attempts are being made to establish similar standards for cereals. Gen- 

 erally, however, field and pot experiments are still to be considered the best 

 means of determining the fertilizer requirements of soils and crops. 



In default of such experiments " soil statics," or keeping account of income 

 and outgo of soil fertility, is recommended as a useful guide in fertilizing. 

 Another guide is furnished by the fact that in normal plants, with the possible 

 exception of Leguminosie, the relative proportions of plant food constituents 

 are approximatelj' nitrogen 100, phosphoric acid 50, potash, 150, and lime SO. 

 "The farmer who reckons out his stock of the principal plant foods per acre 

 for each piece of arable land on the basis of an up-to-date and complete soil 

 analysis, and from this subtracts the quantity of plant foods contained in the 

 forthcoming crop at harvest (allowing about 1 per cent for wastage) on the 



