310 EXPERIMENT STATION RECORD. 



might range from 0.4 to 6 per cent, according to the percentage in the 

 soil, Heinrich uned the oat plant in his expeiiments and analyzed the 

 roots of the crop grown. When he found in the dry roots of oats 

 from 0.08 to 0.1 per cent or less of potash or phosphoric acid and 0.35 

 or less of lime, he concluded that the soil was deficient in these mate- 

 rials and that the necessity of fertilizing with them was indicated.^ 



Dikow^ confirmed Heinrich's results in general, although he em- 

 ployed barle}' and hxed the minimum for phosphoric acid in the roots 

 at 0.13 per cent. 



Atterberg ^ made a long series of investigations, among others with 

 the oat plant. He did not analyze the roots, but the straw and the 

 grain. In his sand cultures, in which he applied the phosphoric acid 

 in the form of a phosphate solution containing all the way from 1 to 7 

 per cent of phosphoric acid, the phosphoric acid in the resulting straw 

 rose proportionately from 0.0:^0 to 0.792 per cent and in the grain 

 from 0.4-4 to 0,95 per cent. At the same time the total yield increased, 

 but the percentage of nitrogen in the straw diminished. He laid 

 special stress on the determination of the ratio between the nitrogen 

 and phosphoric acid and also the potash. He concluded that in the 

 oat grains the ratio of nitrogen to phosphoric acid should approach as 

 nearly as possil^le 100 : 55, and in the oat straw the ratio of nitrogen to 

 potash, lOO : lOO; that is, the percentage of nitrogen should equal that 

 of potash. 



Joulie* presented some general deductions to the effect that from 

 plant analyses (wheat) the fertility and fertilizer needs of the soil 

 could be determined upon; and some of Maercker's researches indi- 

 cate the same conclusion. 



Helmkampf" made a thorough study of Heinrich's method. He 

 did not deny that the method had value, but considered spring wheat 

 a Ijetter plant for experimental work of this kind than the oat plant. 

 He advised, furthermore, that the part of the plant above ground, 

 harvested during the period of bloom, be used for analysis instead of 

 the roots. He did not give any mininuim values for the individual 

 elements, although he stated that when there was an increase in the 

 percentage of potash, phosphoric acid, and nitrogen in the dry matter 

 of the crop as a result of the application of these materials to the plat, 

 the need of these materials was indicated. 



In a more recent article by Atterberg'"' the minima for oats are 

 given as follows: 



^ He made the same application in case of nitrogen as in the ash constituents. 



- Jour. Landw. , 39 (1891 ), p. 134. 



3 Landw. Jahrb., 15 (1886), p. 415; 16 (1887), p. 757; Jour. Landw., 49 (1901), p. 97. 



*Jour. Agr. [Paris], 1889, I, Xo. 1058, p. 89. 



Mour. Landw., 40 (1892), p. 168. 



"Ibid., 49 (1901), pp. 165, 172. 



