BUREAU OF PLANT INDUSTRY. 167 



I\es;carcli Council, with a view to utilizing economically such mate- 

 rials in fertilizer practice. 



The investigation has already shown that trinitrotoluene is poi- 

 sonous to plants and can not be directly used in fertilizers ; that the 

 nitrated celluloses, while not poisonous to plants, are, on the other 

 hand, so insoluble as to leave the nitrogen unavailable to plants, and 

 that aiunionification or nitrification of this material in the soil pro- 

 ceeds with extreme slowness, if at all, under normal conditions. 

 Chemical treatment of this material is therefore being resorted to, 

 and already some very promising results have been obtained, which 

 make the nitrogen of such materials available and would apj)ear to 

 be the basis for the possible utilization of such material in fertilizers. 



FERTILIZER TESTS ON TOBACCO. 



In Maryland a series of fertilizer tests with tobacco which has 

 been in progress for several years was completed, and the results 

 have been published in popular form. It has been found that on the 

 average soil nitrogen is the fertilizer element most needed by the to- 

 bacco crop. Phosphoric acid has not increased the yield, but may 

 improve the ciualit}^ of the tobacco. Under systems of heavy or con- 

 tinuous cropping the tobacco has shown a decided need of potash. 

 Under average conditions a fertilizer suppljang 25 to 30 pounds each 

 of nitrogen and potash and about oO poimds of phosphoric acid per 

 acre will give very profitable i*eturns. The commercial fertilizers 

 commonly used by tobacco growers do not furnish enough nitrogen 

 for the best results. Field tests dealing with the fertilizer require- 

 ments of the principal types of tobacco were continued in the States 

 of New YorK, Pennsylvania, West Virginia, Virginia, and the 

 Carolinas. 



Substantial progress has been made in an investigation of the role 

 of potash in the nutrition of the tobacco plant, including the com- 

 parative effects of the muriate and sulphate on the growth and dc- 

 A'elopment of the plant. It has been established that there are ma- 

 terial differences in the action of these two forms of potash when 

 applied as a fertilizer to tobacco on certain types of soil. 



PLANT-NUTRITION INVESTIGATIONS. 



In the field experunents dealing with the specific effects of crop 

 plants on the yields of crops immediately following, many data have 

 been secured tending to show that under strictly comparable condi- 

 tions corn, tobacco, and potatoes affect very differently the yields of 

 succeeding crops of wheat, oats, and rye. These effects are mani- 

 fested under different fertilizer treatments, but in varying degrees. 

 The crops of corn, tobacco, and potatoes also show similar results 

 when each crop is grown after itself and in rotation Avith the other 

 two. 



In connection with further investigations on the relation of the 

 environmental conditions to the formation of oil in the seeds of plants 

 it has been discovered that, contrary to general belief, sunlight, 

 rather than temperature relations, is the important factor in deter- 

 mining the seasonal development or maturation of plants. This dis- 

 covery of a comparatively simple connection between sunlight and 

 the vegetative and reproductive phases of plant development un- 



