Department of Soil Technology xci 



which different combinations of moisture content and fertilization were 

 used. The results show that any increase of moisture in the soil beyond 

 the quantity required to fill the capillary spaces is not attended by any 

 notable change in the solubility of the plant nutrients aside from the 

 nitrogen, the form and consequent solubility of which constituent is 

 greatly influenced by satunation. The absorption of nutrients by plants 

 is, on the other hand, greatly influenced by the moisture content of the 

 soil above capillary capacity. The influence of moisture content below 

 capillary capacity is now being studied. 



2. A study of the composition and concentration of the imter-soluble 

 material of soils under different methods of treatment. — The main 

 problem has been a study of the formation of nitrates and other water- 

 soluble matter in soils as affected by the growth of certain of the higher 

 plants. The influence of some other conditions have of necessity been 

 studied, in order to eliminate them from the experimental results. The 

 experiments deal with the efl:ect of plant growth on the soil in distinction 

 from the effect of the soil on the plant. The conclusions previously 

 drawn, that certain plants during their early stages of growth exercise a 

 stimulating influence on the formation of nitrates and during the later 

 stages a depressing influence, has been confirmed. Some plants depress 

 nitrification during almost all of their growing period. This is the case 

 with timothy. The nature of the plant, has, moreover, been found to 

 affect the formation of nitrates in the summer following that in which 

 the plants were grown. These findings may have ,a practical bearing on 

 the use of cover crops in orchards and in a study of crop rotations. 



3. Examination of certain properties of an unproductive soil. — This 

 was instigated by the occurrence of a number of poor spots in a piece of 

 soil on the experiment field. These spots do not dift'er in color, com- 

 position, and texture from the more productive parts of the field, but in 

 structure and certain other properties there are differences. The bacterial 

 flora is also different. The correlation of the qualities that distinguish 

 the unproductive spots — as, for example, the deflocculated condition of 

 the particles, the increased absorption, the higher nitrate content, and the 

 greater number of bacteria — ■ gives a basis for studying a combination of 

 properties, one consequent on the other, and for ascertaining whether 

 the amelioration of one condition will lead to a correction of others. 

 With this knowledge it may be possible to avoid more expensive soil 

 treatments by indirect treatments that are inexpensive. 



4. The conditions under which calcium is removed from soils, and the 

 changes that accompany its removal. — The tendency of soils in a humid 

 region to lose their basic constituents may be more or less controllable. 

 The effect of different crops, cultivation, fertilizers, and the like on the 



