FLOWER POT COMPOSITION 155 



isms and is not available for plants until the ratio approaches the 1:10 

 constant. 



The work of N'iljoen and Fred (15) in which wood and wood pnip cellu- 

 lose were used sho\\ s a harmful efl'ect on plants. These investigators agree 

 that the harmful effect was due to the need for nitrogen liy the organisms 

 decomposing the cellulose. As the paper pots are of tiiis form of cellulose, 

 there is no doubt that the same processes were taking place. 



Knott and Jeft'ries (9)^ also working with paper flower pots nuide actual 

 determinations of nitrate j^resent in the soil. Their data sho>y that in th«? 

 process of decomposing the cellulose, the nitrate nitrogen of the soil had been 

 reduced six-sevenths. Their recommendation that the effect of nitrate defi- 

 ciency may be overcome by periodic applications of a nitrate solution is in 

 agreement with the data of Table 4 in this paper. 



Knott and Jeffries (9) recommend the treating of paper bands or pots 

 with wax, asphalt, or other chemicals. The rate of decomposition will then 

 be reduced and there will be less danger of nitrate starvation. 



The effect of a nitrogen deficiency can be overcome by applications of 

 available nitrogen. It was the purpose of the writer, however, not to remedy 

 the effect, but to remove the cause. It was reasoned that a paper pot in 

 which the fibers are so well protected that decomposition can not occur should 

 grow as good plants as those grown in glass containers. 



Many different materials were used\ some of which gave a partial degree 

 of protection. Substances, which usually jirotect wood and are subjected to 

 wide fluctuations of temperature and moisture, could not withstand the in- 

 roads of the weathering processes taking place in the humid atmosphere of 

 the soil, a soil with a slight acid reaction, and replete with biochemical proc- 

 esses set up by the micro-organisms of the soil. 



Inasmuch as any water-proofing material would decrease the porosity 

 of the paper pot, the trend of pot comjiosition would be to approach a 

 structure that resembled glass. Hence, in all tests, glass containers as well 

 as clay flower pots were used as checks. If glass produced poorer plants 

 than those grown in clay pots, the practicability of the residts would be 

 doubtful. 



The materials used for water-jaroofing were gi\en careful consideration. 

 Combinations of treatments were made, including inside and outside surfaces 

 and treatments before and after the pots were formed. Special grades of 

 paraiffn, sodium silicate, lacquer, varnish, Bakelite varnish, cellophane, and 

 asphalt were used. Pots were provided with plant nutrients and also chem- 

 icals toxic to organisms (mercuric chloride and copper sulfate) incorporated 

 in the paper before the coatings were applied. 



Tomato and calendula seedlings were used as indicator plants as they 

 grow fairly rapidly and the leaves quickly turn yellow when a nitrogen de- 

 ficiency exists. As the testing progressed and many of the treatments to the 

 pajier were eliminated, the final test was carried out with geranium plants in 

 four-inch pots. The geranium grows slowly and did not become pot-bound 



' The program of testing paper pots with various water-proofing materials was 

 well advanced before the publication of the good work done by Knott and Jeffries. 



■* The writer is indebted to :Mr. E. L. Connolly of Bird & Son for the treated 

 paper pots and to the Bakelite Corporation for furnishing this laboratory with three 

 Bakelite varnishes. 



