in the old barks than in fresh sawdust and shavings. If they had been com- 

 pared directly with composted sawdust in this respect, the story might 

 have been different ( 1 ) . 



Effects of Old Bark-Soil Mixtures 

 Without Fertilizer on Bean Yields 



Old hardwood and old softwood bark were mixed each with soil in the 

 proportion of % bark to % soil and Tiny wax beans grown in them in 

 comparison to soil only as control. Fertilizer was omitted in order to de- 

 termine something of the effects of the bark alone on plant growth. The 

 plants were grown in ten-inch pots, with two plants per pot and twenty 

 pots per treatment. The results in yield of seed appear in Table 4. The 

 better yield of the plants grown in soil alone further strengthens the case 



Table 4. Yields of Seeds of Wax Beans Grown !n Soil-Bark Mixtures, No Fertilizer 



* Significantly greater than other yields at the 5 percent level. 



that most of these organic soil supplements will not support or promote 

 good plant growth without liberal amounts of fertilizer. This is still further 

 emphasized and supported by the results on tomatoes given in the following 

 section. 



Effects on Tomato Yields of Pure Old Bark 

 Compared to Soil With Added Fertilizer 



This was an experiment to determine something about the influence of bark 

 alone (not mixed with soil) on plant growth. The two old barks were 

 studied in comparison with pure peat, and with soil only as control. The 

 materials were each placed in 10 glazed crocks of 2-gal. capacity. Before 

 planting, 20 grams of 5-10-10 fertilizer was mixed with the contents of 

 each crock. Young tomato plants of the New Hampshire Victor variety were 

 transplanted, one to each container. Early in the course of this experiment 

 all of the plants in pure peat died, evidently because of the low pH. There- 

 fore, no yield data is available for the plants in this material. After the 

 other plants had been growing for nearly two months 5 grams of ammonium 

 nitrate were added to each crock as supplementary nutrient. 



As the plants matured, records were kept of the yields of fresh ripe 

 fruit from each plant. The yields are given in Table 5, as well as the aver- 

 age weight of the individual fruits from each material. The average yields 

 for both bark treatments were considerably greater than for the soil con- 



