204 SOIL SCIENCE [Bot. Absts., Vol. VI, 



and unlimed plats was practically equal. 3. The addition of 320 pounds of nitrate of soda per 

 acre to the plats receiving 16 tons of manure per acre increased the crop yields indicating 

 that nitrogen was a limiting factor. The authors conclude "The results of these experiments 

 would seem to show beyond a doubt, that for the lighter coastal plain soils, lime has very 

 little place in rotations which entirely omit legumes."— H. N. Vinall. 



INFLUENCE OF BIOLOGICAL AGENTS 



1374. Albrecht, William Albert. Symbiotic nitrogen fixation as influenced by the nitro- 

 gen in the soil. Soil Sci. 9: 275-327. 4 pi., 3 fig. 1920.— Soybeans and cowpeas were grown 

 in pots in a soil low in nitrogen and organic matter to which varying amounts of sodium nitrate 

 or clover tops were added. Nitrogen fixation was determined by analyzing for the total nitro- 

 gen before and after growth. Nitrates up to 1500 pounds of sodium nitrate per acre did not 

 prove injurious to nitrogen fixation and did not affect the nodule production appreciably. 

 In some cases the decaying organic matter caused heavy losses in nitrogen but after the loss 

 ceased, large nitrogen fixation occurred. The organic matter added increased the nitrogen 

 fixed by cowpeas. The maximum average fixation for duplicate pots of 5 cowpea plants was 

 1295 mgm.— W. J. Robbins. 



1375. Headden, W. P. Some soil studies. Proc. Soc. Promotion Agric. Sci. 39: 22-38. 

 1919. — The accumulation of excess amounts of nitric nitrogen in the soil is given as the cause 

 of low yields and poor quality in both the sugar beet and wheat crops of Colorado. An increase 

 of 40 parts per million of nitric nitrogen in the surface foot of soil, depressed the sugar con- 

 tent of beets from 15.4 to 11.9 per cent and produced other unfavorable results. It was found 

 that a certain soil which had a maximum of 20.5 parts per million on March 4 showed a steady 

 increase of nitric nitrogen during the summer. On August 25 the minimum was 47 parts per 

 million and the maximum 333 parts per million of nitric nitrogen. The author believes that 

 certain Colorado soils have the power to fix atmospheric nitrogen converting it into protein 

 nitrogen through the agency of their bacterial flora, the Azotobacter. In experiments with 

 soil taken from the fields he found a maximum nitrogen fixation of 124 parts per million in 

 48 days. This rate of fixation would add 1.5 tons of protein matter to the acre foot of soil in 

 48 days.— H. N. Vinall. 



1376. Lipman, J. C, and A. W. Blair. Field experiments on the availability of nitrogenous 

 fertilizers, 1908-1917. Soil Sci. 9: 371-392. 1920.— A report is made of the second 5 year per- 

 iod of a study of the availability and nitrogen losses of various nitrogenous materials under a 

 rotation of corn, oats, wheat and two years timothy on forty 1 /20 acre plots in limed and un- 

 limed condition. The average yields of dry matter and the percentage of nitrogen recovered 

 were greater with mineral than organic materials. From 1913-17, an average loss of 66 per 

 cent of the applied nitrogen occurred. The limed plots during 10 years lost 250 pounds more 

 nitrogen than the unlimed. The supply of nitrogen and carbon was best maintained on the 

 plots receiving farm manure. The work emphasizes the difficulty of maintaining the nitrogen 

 supply of the soil at a high level under continuous cropping to non-leguminous crops, even 

 when commercial fertilizers are supplied. — W. J. Robbins. 



1377. McCall, A. C, and A. M. Smith. Effect of manure-sulphur composts upon the 

 availability of the potassium of green sand. Jour. Agric. Res. 19: 239-256. 1 fig. 1920.— Two 

 green sands, one containing 5.88 per cent of potassium, the other 1.42 per cent were used to 

 study the effect of sulphofication upon the solubility of the potassium. In composts con- 

 sisting of green sand, manure and soil in different proportions, an appreciable amount of the 

 potassium was made water-soluble through sulphofication. The compost containing the 

 largest proportion of manure developed the highest degree of acidity, oxidized the greatest 

 amount of sulphur, and produced the largest quantity of water-soluble potassium, while the 

 composts in which soil was substituted for a part of the manure developed less acidity, oxi- 

 dized less sulphur and produced a smaller amount of soluble potassium. When all the manure 

 was replaced by soil the rate of sulphofication was so slow that at the end of 23 weeks only a 



