' EXPERIMENT STATION REPORTS. 275 



3-4 (SKH.PO^— 3Ca(N0.),— 4MgSOJ. This shows that there is a best 

 or optimum proportion of salts, and not as formerly believed that the 

 proportion could vary widely without apparent detriment to the plant. 

 Still another feature of importance is the total concentration of the 

 solution. Some may have a total concentration too weak to support 

 life and some too strong. A certain concentration is essential, and 

 this concentration determines the proportion of salts best suited for the 

 idant under study. 



In applying these findings to soil culture it is readily seen that there 

 will be many conditions less easy to control than in the case of water 

 cultures. Studies have been made and are being continued to determine 

 if possible what total concentration of the three salts and what propor- 

 tion of salts will give the best growth in pure quartz sand, ordinary 

 sand and soil cultures and what influence adsorption, soil grain size, the 

 presence of chemicals, organic substance and other factors have on 

 this concentration and proportion. 



As far as can be learned no other station is carrying on such a prob- 

 lem. Its practical application and its universal value should make this 

 investigation one of importance. The work has so developed, has opened 

 up so many lines of study, besides showing the need of a restudy of 

 certain phases, and has become so large that the need of technical as- 

 sistance has been felt for the past two years, and especially so the past 

 year. It is suggested therefore, that two half-time graduate assistant- 

 ships or one full-time assistantship be established, these students or this 

 assistant to devote the time to the study of some phase of the general 

 problem. 



Preliminary studies have been made and more extended ones are be- 

 ing instituted to determine if i^ossible what salts and what proportion 

 of salts are needed to improve the soil solution for plant growth. The 

 soil solution is obtained by the pressure method. This Avork is done in 

 cooperation with Mr. ]\rorgan of the Soil Bacteriological division of 

 the Bacteriological department who is to supply the soil solution. 

 These studies should indicate what to do with "sick" soils from which 

 the soil solution has been pressed. 



Other problems are pressing, such as (1) Physiological studies of the 

 effects of poisons on plants with reference to their use in the eradication 

 of Canada thistle, wild mustard, etc., from fields, (2) Nutrition as relat- 

 ed to physiological diseases, and (3) the water requirement of plants 

 with special reference to the period of growth in which the most water 

 is necessary, the effect of nutrients on Avater requirement and the power 

 of the soil to supply moisture to the plant. In regard to this latter 

 l)hase a simple and efficient method has been devised to study this rela- 

 lion between the soil moisture and the growth of plants in the field. 

 This work was done under my direction by O. E. Harrington as a minor 

 requirement for the M. S. degree. The paper Avill soon appear in 

 Physiological Researches under the title '^Depression of the freezing- 

 point in triturated plant tissues and the magnitude of this depression 

 as related to soil moisture." 



The effect of a nutrient solution lacking one element on photosynthesis 

 in corn and cucundjer plants has been studied with the result that 

 many interesting facts have been obtained and new lines of investigation 



