514 EXPERIMENT STATION RECORD. fVol. t3 



field demonstration with oats and tlio one with corn Indicated that its addi- 

 tion is not ossontial to get niuxinmm results. The response from the addition 

 of phosphorus is explained in two ways, namely, that the extreme acidity of 

 the soil caused the loss of the original phosphorus through leaching, and that 

 the original phosphorus is still present in the soil, but is combined with other 

 elements to form compounds in which it is unavailable. The increase in 

 growth from the treatment with a nitrogen fertilizer is explained by the fact 

 that a soil which remains barren of vegetation for a number of years loses 

 its nitrogen through leaching. The effect of lime alone in recreation of the 

 soil was much more noticeable with oats than with corn. 



The preliminary field tests showed that alsike clover becomes more readily 

 establishefl than red clover. Jar culture tests indicated that the soil can not 

 be reclaimed by deep tillage. Field observations during the sunuuer of 1919 

 indicated that not all of the damage to growing crops occurs after the con- 

 tamination of the soil, but is due to poisonous gases when they come in con- 

 tact with the green tissues of the plants. Of the common crops, barley is the 

 most sensitive. 



The effect of nitrogen-fixing organisms and nucleic acid derivatives on 

 plant growth, W. B. Bottomley {Pmc. Roy. Soc. [London], Scr. B, 91 {1920), 

 No. B 636, pp. 83-95; abs. in Jour. Soc. Chcm. Indus., 39 (1920), No. 5, p. 

 200A). — Continuing experiments previously noted (E. S. R., 33, p. 124; 37, p. 

 719) on the influence of a water extract of bacterized peat on plants in water 

 cultures, experiments are reported on the influence of the individual constitu- 

 ents of the bacterized peat extract on the growth of Lemna minor. 



A pure growth of Azotohacter chroococcum was sterilized in the autoclave 

 in the presence of water and adde<l in small known amounts to the L. minor 

 plants in nutritive solution. There was an increase in rate of growth and in 

 dry weight of the crop in six weeks over unti"eated plants. Similar results 

 were obtained with Bacillus radicicola. An extract of the crude nucleic acid 

 derivatives and of the adenin-uracil fraction from raw i>eat also stimulatetl 

 growth. 



When the extract of the crude nucleic acid deri\'atives was added along with 

 the growth of A. chroococcum to the same plants the inci"ease in growth exceeded 

 that of the total produced by the two substances added separately. " It 

 would therefore appear that the growth-promoting substances in these two 

 liquids are dis.similar in their action upon the plant, and that they are in some 

 manner complementary to one another." 



It was further found that " the ash of the nucleic acid derivatives and the 

 Azotobacter had evidently not the slightest effect on the growth of L. minor, 

 and the benefical results following the addition of these materials can only be 

 attributed to their organic constituents." 



The influence of nitrates on the growtli of Azotobacter, T. L. Hills 

 {Pennsylvania Sta. Rpt. 1916, pp. 811-317). — Soil and liquid cultures contain- 

 ing small amounts of potassium, sodium, and calcium nitrates were found to 

 cause an increase in numbers of Azotobacter in pure culture over control 

 cultures containing no nitrate. 



It was found that an increasing concentnition of the nitrates continued to 

 favor Azotobacter growth up to a certain limit, viz, 1 per cent in the case of 

 potassium nitrate and 0.5 per cent in the case of sodium nitrate and calcium 

 nitrate. Higher concentrations than these retanled the growth, and a limit 

 was reached at which Azotobacter growth ceased altogether. Calcium nitrate 

 was apparently the most toxic. 



These results are thought to have a bearing on the niter spot theories ad- 

 vanced by the Colorado and Utah Experiment Stations. " That these ' niter 



