46 CONTROL SERIES No. 54 



VEGETATION POT EXPERIMENT TO STUDY NITROGEN 

 AVAILABILITY. 



This is a report of results of a vegetation pot experiment to study the availa- 

 bility of the nitrogen in certain processed low-grade organic materials, garbage 

 tankage and other fertilizing materials valued chiefly for their content of organic 

 nitrogen. Some of these results terminate three years' experiments in which 

 new samples have been secured through trade channels each year. This method 

 was adopted in order to give credit for any improvement in the quality of product 

 due to improved methods of manufacture. Certain seeds of plants containing 

 varying amounts of nitrogen were included this season ujion request of members 

 of the fertilizer industry. These oil-extracted seed products are used largely 

 as the organic portion of the nitrogen content of tobacco fertilizers used in grow- 

 ing cigar wrapper and binder types of leaf. 



The following table gives the average composition of the products under 

 experiment from a fertilizer standj^oint. 



Outline of the Experiment. 



The experiment was planned to show in Series I the availability of the total 

 nitrogen in each product tested, and in Series II the availability of the water in- 

 soluble nitrogen in those products which contained aj)] reciable quantities of 

 nitrogen in this form, each product being washed with successive portions of 

 water until practically free from water soluble nitrogen. 



Each i:)ot received 38 pounds of soil mixtvire made up of one part loam and 

 two parts sifted sand. The loam was taken from the west end of Plot 9, North 

 Soil Test, and showed the presence of .09 per cent nitrogen. No nitrogen ferti- 

 lizer or animal manure has been applied to this soil since 1890, the annual ferti- 

 lizer api)lication during this period consisting of 320 pounds of superphosphate 

 and 160 pounds of muriate of potash per acre. 



The fertilizer was mixed with the entire amount of soil in each pot, the amount 

 of each material used being as follows: 24.4 grams of fine ground limestone, 

 16.33 grams of muriate of potash, 15 grams of potash-magnesium sulfate, 8.2 

 grams of high grade sulfate of potash, and 25 grams each of 16% superphosphate 

 and basic slag phosphate. In case of the Peruvian Guano and the two Distillery 

 Waste Fertilizers, the applications of potash and phosphoric acid were governed 

 by the analyses of the products so as to insure the same amount of plan': food. 

 The nitrogen-con':aining materials were applied in unit quantity to supply .42 

 grams of nitrogen per pot, the same as in previous experiments. 



Water was supplied to the growing plants through subirrigation and surface 

 application when nece.ssary. Until hot weather the moisture was held at 50 

 per cent of the water-holding capacity of the soil; during hot summer weather 

 it was increased to 60 per cent. The pots were weighed twice each week to main- 

 tain this constant, a measured amount of water being applied at other times as 

 the need became apparent. 



Japanese millet was the croj) grown, seven seeds per hill, five hills per pot, 

 later thinned to two plants per hill or ten ])lants per pot. The crop was harvested 

 when in milk and all jjots had a full stand of plants. 



In the preparation of the soil, fertilizer application, and general care of the ex- 

 periment through harvesting and drying, credit is given to George J. Larsinos. 

 H. Robert DeRose and Albert F. Spelman assisted in the chemical analysis of 

 the fertilizing materials, and H. Robert DeRose assisted in the dry matter and 

 nitrogen tests on the crop harvested. 



