SOILS — FERTILIZERS. 721 



constituted 1.1 per cent of the total number of samples taken and their total 

 nitrate content was approximately 10 per cent of the total nitrate as contained 

 in all samples," 



Studies on the influence of cultivation on nitrate development in 11 tenth- 

 acre plats of silt loam soil showed that the highest nitrate content was found 

 in early spring. Two months later there was only a small amount left, but it 

 was in the same proportion as in April and at harvest time there was still less. 

 In November, two and one-half months after harvest there was a slight increase 

 but not until the fall rains came was there a very material development. The 

 following spring there was a marked increase in those plats which were fall 

 plowed. 



Duty of water experiments at the Grandview substation on corn and potatoes 

 during a season with a rainfall of 7.35 in. gave results showing that the yield 

 of corn per acre was greatest with an 8-in. application of water, followed in 

 order by 4, 12, 20, and 16 in. applications. The yield per acre-inch of water 

 applied, however, decreased steadily as the size of application increased. The 

 yield of potatoes per acre increased as the application increased from 4 to 21 

 in., while the yield per acre-inch decreased as the application increased. 



A study of the percolation of water in coarse sand, medium sandy loam, and 

 fine sandy loam showed that the absorptive power of the soil gradually decreases 

 " as the time increases with the application of water." 



The water- supplying power of the soil as indicated by osmometers, H. E. 

 Pulling and B. E. Livingston (Carnegie Inst. WasJilngton Pub. 204 {1915), pp. 

 49-84, figs. 2). — Preliminary experiments on the power of an artificial soil 

 mixture, consisting of 3 parts of sand and 1 part of dry loam, to supply water 

 to the roots of plants, as indicated by osmometers prepared from ordinary 

 thistle tubes with the large opening closed by a collodion membrane, are 

 reported. Cane sugar solution was used in these osmotic cells. The osmom- 

 eters were tested both in water and in the soil mixture. The collodion mem- 

 branes were found to be suitable for the making of osmotic cells for such 

 experiments. 



Packing of the soil was found to be of prime importance in determining its 

 water-supplying power. "The lack of suitable methods for obtaining strictly 

 comparable packing of a number of soil samples is one of the main obstacles to 

 a rapid investigation of the field thus opened." 



In this connection it is also considered evident that " it is the percentage of 

 contained soil moisture on the basis of actual soil volume, and not this percent- 

 age calculated on dry weight of the soil, which plays an important part in 

 determining the efficiency of the soil as a source of water supply to growing 

 plants. . . . The influence of temperature upon the water-supplying power of 

 the soil, or at least upon its measurement, appears to be of great importance." 



It was further found that the osmotic solution used (5-weight molecular cane 

 sugar) was too concentrated to permit the measurement of the water-supplying 

 power of the soil mixtures with the water content much above their critical 

 optimum. Below the critical moisture content the tests gave quite satisfactory 

 results. " Of fundamental interest is the fact that the critical point in soil- 

 moisture content appears to be approximately the same as that emphasized as 

 the critical optimum w^ater content by workers in other lines of soil physics." 



The freezing' point m.etliod as a new means of measuring th.e concentra- 

 tion of the soil solution directly in the soil, G. J. Bouyoucos and M. M. Mc- 

 CooL (Michigau Sfa. Tech Bid. 2/, {1915), pp. 44, fi9»- 2).— This bulletin reports 

 the details of experiments previously noted (E. S. R., 34, p. 419). In addition 

 to the results noted in the previous report it was found that, at the low moisture 



