54 CONTROL SERIES No. 51 



Outline of the Experiment 



Each pot received 38 pounds of soil mixture (one part loam from nitrogen 

 deficient soil, Plot 9, North Soil Test, West End, and three parts of sifted sand). 

 The fertihzers were mixed with the entire amount of soil in each pot, the amount of 

 each material used being as follows: 14 grams of fine ground limestone, 5 grams 

 each of muriate of potash and potash-magnesium sulfate, 23^ grams of high-grade 

 sulfate of potash, 18 grams each of 16% superphosphate (acid phosphate) and 

 basic slag phosphate. The nitrogen containing materials were applied in unit 

 quantity sufficient to supply .42 grams of nitrogen. 



The experiment was run in two series to show (1) the availability of the total 

 nitrogen and (2) the availabihty of the water insoluble nitrogen. Necessary checks 

 were run mth double the amount of nitrogen from dried red blood, the standard 

 nitrogen source, in order to prove that in the minimum nitrogen applications the 

 full effect of the nitrogen would be secured. Checks were also run by using 

 increased amounts of the basic fertilizer appUcation (phosphoric acid and potash) . 



Water was supplied by both sub-irrigation and surface appUcation in amounts 

 representing 50 per cent of the water holding capacity of the soil mixture until hot 

 weather when it was increased to 60 per cent. 



Japanese millet was the crop grown. All pots had ten plants when harvested 

 with the following exceptions, aU of which had only nine plants per pot : 17, 26, 56, 

 62, 65, 76, 83, 96. In early August the lower leaves of all of the plants turned 

 yellow. This did not prevent the further growth of the main stallc and upper 

 leaves, but may have resulted in less dry matter yield and nitrogen recovery. As 

 this condition appeared to be uniform on all pots, however, it probably would not 

 interfere in making relative comparisons of both the dry matter yields and the 

 nitrogen recovered. 



With the exceptions noted above, the experiment was conducted the same 

 as described on pages 11 and 12, Control Bulletin 25. 



In the preparation of the soil, fertilizer appUcation, and general care of the 

 experiment, including the harvesting of the crop, credit should be given to George 

 J. Larsinos, a graduate student in the Department of Agronomy of the Massa- 

 chusetts Agricultural College. 



The following table shows the yield of dry matter and the nitrogen recovered in 

 the above-ground parts of the plant; the nitrogen availability of each product, 

 from the standpoint of both total and water insoluble nitrogen and on the basis of 

 yield of dry matter and nitrogen recovered from dried red blood being placed at 

 80. The activity of the total and water insoluble nitrogen in each product as 

 shown by the two laboratory methods is also given. 



