EXPERIMENT STATION REPORTS. 295 



nutrient or standard solutions are well taken. It is likely that this so- 

 lution will supplant the four, live, or six salt solutions, since it 

 contains every one of the elements said to be absolutely essential, 

 and simplifies the routine work necessary for a study of salt ratios. 

 There has been considerable criticism of water culture methods in gen- 

 eral, and some of these have been well founded. Most of the work al- 

 ready published on the matter consists of but little more than growing 

 plants in different solutions and recording the differences in height and 

 judging a plant from a few other merely qualitative criteria. The work 

 should be more scientific and an attempt be made to analyze the results 

 produced on plants such as the effect on the physiological processes, etc. 

 Sand, soil, and field studies should be made and a practical applica- 

 tion brought to the front. The lack of control methods becomes more 

 apparent as field studies are approached and this is where but little work 

 of a quantitative nature has been done. 



In regard to salt ratios or physiological balance, it is true that some 

 ratios in a single series cause better growth than others, and one can be 

 found better than any other but no two or more series of cultures seem 

 to agree on any one set of the ratios. However, it can be said that they 

 are located near each other in the same restricted area. Variations in 

 individual plants, difference in vigor, susceptibility, and different en- 

 vironmental conditions might account for this lack of identical agree- 

 ment. The problem is open for further study. 



In regard to solute absorption in distilled water nutrient solution, 

 this much may be said. Cryoscopic and conductivity determinations 

 have shown that where the ratios are such as give the best yields in 

 wheat the concentration of the solution has been reduced the most and 

 when the ratios have given the poorest yields the concentration has 

 changed but little, all of which leads to the belief that the optimum 

 ratio or physiological balance tends towards a more efficient absorp- 

 tion. 



From the work with distilled water, the next logical advance would 

 be studies with the soil solution. The soil solution was supplied by the 

 Bacteriological Department, through the courtesy of Mr. Morgan, who 

 cooperated in this investigation. The subject matter has been brought 

 together and is ready to be passed on for publication under the title, 

 ''Physiological Balance in the Soil Solution." 



The soils, one fertile and one infertile, were extracted. These two 

 different solutions formed the basis of three experiments. The solution 

 from the poor soil possessed a low initial concentration and was treated 

 with all possible ratios of three salts varying in increments of 10 per- 

 cent. This study showed what ratio of salts in this particular soil so- 

 lution gave the best growth and greatest yield, and when compared with 

 the best ratio in a distilled water culture showed that an excess of potas-' 

 slum and phosphoric acid was beneficial. When acid potassium phosphate 

 in the dried form was added to a sample of soil similar to that from which 

 the solution was extracted it gave a yield of wheat considerably above the 

 control. This seems to show that a study of the soil solution indicates the 

 chemical needs of the soil from wliich the solution was extracted. 



Next the good soil solution was treated in the same manner. Its 

 initial concentration was high. A different ratio of salts proved to give 

 the highest yield. When compared with the ratio in distilled water cul- 



