Feb. II, 1918 Effect of Season and Crop Growth on Soil Extract 317 



Bogue (j) has published a brief investigation in which he leached 

 four soils with water and also studied their absorptive capacity for 

 potassium and phosphates. From his work he agreed with Whitney 

 and Cameron that the composition of the soil moisture is not influenced 

 by the chemical composition of the soil, but instead is dependent on the 

 mechanical texture of the individual soil. 



Jensen {32) reported a series of observations on eight sugar-beet plots 

 at Rocky Ford, Colo. The methods of investigation employed were 

 those of the U. S. Bureau of Soils {50). The plots receiving composted 

 manure showed nearly twice as much water-soluble potash in the surface 

 foot as did any of the other plots. The seasonal averages of this element 

 were not appreciably influenced by any other fertilizer treatment. There 

 was a decrease noted in the quantity of water-soluble potash from the 

 middle of May till the middle of July. After that time the quantity 

 increased to approximately the amount that had been found earlier in 

 the season. None of the treatments resulted in a marked increase of 

 soluble phosphates, and the variation in this compound was less than 

 in any other element measured. 



Jordan {33) has recently published the results of an investigation in 

 which nine soils were analyzed by complete analysis, acid extraction 

 with hydrochloric acid of 1.115 specific gravity, 10 days' leaching with 

 water, N/200 and A^/25 hydrochloric acid, and five hours' extraction 

 with the last three solutions. Vegetation experiments were conducted 

 with the soils in the greenhouse during two years. At the close of this 

 time it was impossible to establish any relationship between any of the 

 elements determined and the crop-producing capacity. There appeared 

 to be a slight relationship between the total soluble matter in the soil 

 and crop production, but it was not consistent in all cases. The final 

 conclusion was that no method had been developed by which the fer- 

 tility of a soil could be measured through laboratory investigation. 



Harris and Butt (24), working in Utah, have studied the effect of 

 varying amounts of irrigation water upon the development of nitrates 

 and soluble salts in cropped and fallow soils. They found notable 

 differences between the cropped soil and the fallow duplicate, but did 

 not find that these differences were related to variation in the crop yield. 



SCOPE OF THE INVESTIGATION 



The foregoing discussion indicates the contradictory nature of the 

 results already obtained. Two of these moot points especially open to 

 further study are : 



1. The relationship between the soluble soil nutrients in cropped and 

 uncropped soils. 



2. The relationship between the soil extract and the crop produced 

 thereon. 



These questions are the subject of the present study. 



