151. MASS. EXPERIMENT STATION Bl'LLETIN 277 



The nitrogen ai)i)lie{l to the yi.iper ])ots, even after the plants were 

 clieeked in gTOwtli, was sufricient to bring the plants to a lieiglit practically 

 ecpial to that of the plants in clay pots. That there was sufficient nitrogen in 

 the soil uhen the seedling tomatoes were potted is shown by the fact that the 

 clay pots receiving the animoniuni sulfate solution produced no better plants 

 than were obtained in clay pots to which no nitrogen had been added. 



In practically every case the loss of green color by the foliage of the 

 plants in pajjer pots was preceded by a softening of the pot, indicating that 

 decomposition of the pot had started. Heavier coatings of paraffin prolonged 

 the stiffness of the pot, thereby insviring good gro\\th of the plants for a 

 longer period than was possible in the paper pots protected with a light 

 coating of paraffin. That the decomposition of the paper fibers is indirectly 

 the cause of the nitrogen deficiency is substantiated by the results of many 

 investigators who have studied the effect of decomposing cellulose on plane 

 growth. This investigation, in its latter phase, indicates that when the paper 

 fibers are so well protected that decomposition is impossible, no nitrogen 

 deficiency will occur. The direct cause of the shortage of available nitrogen 

 is the superior ability of the soil micro-organisms, producing the decomposi- 

 tion, to assimilate the nitrogen of the soil in competition with the plant. 



In this case, the mass of soil was practically surrounded by decomposable 

 cellulose. The literature on the effect of decomjiosing cellulose on plant 

 growth is concerned with cellulose incorporated in the soil. However, as the 

 paper soon becomes water-soaked and eva])orates water from its outside sur- 

 face, the cellulose truly becomes a constituent of the soil, and it is not im- 

 probable that the same or similar processes of cellulose decomposition are 

 involved. It must also be kept in mind that when decomposition of the pot 

 has reached the point where the yiot becomes water-soaked, this area acts as 

 an evaporating surface and there would be a movement of the soil solution 

 to this area. Furthermore, the feeding roots are close to the inside surface 

 of the pot, the very region where microbial activity is the highest and where 

 there would be the greatest competition for nutrients of the soil. 



The recent work of Collison and Conn (2) confirms the explanation of 

 earlier investigators, i. e., "that the presence of highly carbonaceous material 

 stimulates the activities of micro-organisms which compete with the plants 

 for the available nitrogen and in that way cause a nitrogen shortage in the 

 medium." Of these investigators may be mentioned Kriiger and Schneide- 

 wind (10) (11) who first proposed the theory. Pfeiffer and Lemmermann 

 (13) decided tliat the micro-organisms used the nitrogen as a necessary food 

 for their existence. Kellerman and Wright (8) came to a similar conclusion. 

 \\hen they created a state of malnutrition in citrous seedlings by addition of 

 cellulose to the soil. Hill (6) studied the Icngtii of time that cellulose de- 

 pressed the nitrate content of a soil. Doryland (4) and Rahn (14) concluded 

 that the supply of soil nitrogen may be utilized by the micro-organi.sms to 

 the extent that it may become a limiting factor to their activities. Allison (1) 

 makes an application of the nitrogen-carbon ratio wliicli lias the a])])roximate 

 constant of 1:10 in humid regions. When this ratio is widened by the intro- 

 duction of a highly carbonaceous substance there is an increased activity of 

 micro-organisms to narrow the new ratio in the process of which the relative- 

 ly small amount of nitrogen is tied up in the protein substance of the or- 

 ganisms. This nitrogen may be utilized over and over again by these organ- 



