Feb. II, i9i8{ Effect of Season and Crop Growth on Soil Extract 313 



rium of the solution quickly readjusted itself, at least as quickly as the 

 plant disturbed it by withdrawing nutrients. 



It was therefore believed that the controlling factors in fertility were 

 moisture and the physical condition of the soil, and not fertilizers or 

 plant nutrients. 



This was an entirely new viewpoint in soil investigations and has 

 proved extremely stimulating to other workers, though it should be 

 stated that Cameron {10-12) has somewhat modified his conclusions in 

 his later writings. 



The first portion of the work of King {34), which had been carried on 

 concurrently with that of Whitney and Cameron (<5i) in the Bureau of 

 Soils, appeared a year later. It consisted of three papers, which were 

 published privately by the author, while the remaining three were issued 

 from the Bureau of Soils {35). 



This work constitutes the most extensive investigation so far carried 

 out on the water extracts of soils. The methods employed were the 

 same as those used in the previous investigation of Whitney and Cam- 

 eron {61). The analyses in the preliminary work were performed on the 

 fresh samples of field soil, but later in the investigation, despite the large 

 error involved, oven-dried samples were employed. 



The work of the first season was largely of a preliminary nature and 

 was principally carried out at Goldsboro, N. C. Additional samples 

 were taken in Georgia, Virginia, Maryland, New Jersey, Pennsylvania, 

 and Wisconsin. In the second season the work was more intensive and 

 consisted of a study of eight soil types in the four States of North Caro- 

 lina, Maryland, Pennsylvania, and Wisconsin. The crops used were 

 cotton, peas, beans, corn, and oats. 



Applications of fertilizer consisting of 5, 10, and 15 tons of manure 

 and 300 pounds of guano were made to two crops, com and potatoes. 

 Analyses of the water extracts of the soils from these varied crops were 

 made from three to six times during the season, as well as numerous 

 extracts of the plant saps. 



In general, the results and conclusions drawn were diametrically 

 opposed to those of Whitney and Cameron. Relatively large amounts 

 of nutrients were found to be either actually in solution or in such form 

 that they entered into solution when diluted with distilled water. It 

 was also shown that the application of fertilizers materially increased 

 the amounts of salts recovered from the soils. The largest amounts of 

 salts were, as a whole, found where the yields were largest, and the same 

 results were obtained from the examination of the plant sap. 



The influence of farm manures was found to increase not only the crop 

 but also the amounts of soluble salts which could be recovered from the 

 soil. 



27809°— 18 2 



