Food for absent. On the other hand, when the nitrogen was omitted 

 Plants from the dressings, there was practically a complete failure 

 166 o f crO p. The experiments show that these soils require 

 before everything that nitrogen shall be supplied, then phos- 

 phoric acid and potash. In the first experiment, the yield 

 without nitrogen fell from 99 grams of the grain to 1 1 grams 

 of grain, and that when the phosphoric acid and potash were 

 omitted the yield fell only about 17 to 19 per cent. 



In the second experiment, the results are very similar 

 to those of the first. The soil not being poor in phosphoric 

 acid and potash, but extremely poor in nitrogen; in this soil, 

 also, if before everything the dressing is not rich in nitrogen, 

 no increase is to be obtained on the field without nitrogenous 

 fertilizer. 



In the third experiment, where potash and phosphate 

 fertilizers without nitrogen were applied, the plants suffered 

 so badly from nitrogen hunger that only 5 grams of grain 

 have been harvested from the pot. With the addition of ni- 

 trogen in the form of Nitrate of Soda in the complete dress- 

 ing, the produce was no less than 88 grams of grain. 



In the fourth experiment, there are also distinct indica- 

 tions of hunger for nitrogen, besides hunger for phosphoric 

 acid, and though less striking, a clearly perceptible hunger 

 for potash. 



A review of the four experiments shows very clearly 

 the plant-food deficiencies of the several soils. The results 

 of these experiments would be still more attractive and inter- 

 esting if the living plants could be observed as they showed 

 indications of the hunger of the plants for nitrogen, and like- 

 wise if it exists in a high degree, their hunger for phosphoric 

 acid and potash are to be recognized. Plants hungering for 

 nitrogen are of a yellowish-green color; if very greatly hun- 

 gering, they are of a greenish-yellow. Hunger for phosphoric 

 acid makes itself observable by characteristic brown stripes 

 on the leaves, and hunger for potash is to be recognized by 

 yellow spots, gradually becoming brown, on the leaves, and 

 by the flaccid appearance of thf plants. 



A further evidence of the need for nitrogen is given by 

 the yields of grain obtained from vegetation experiments on 

 II other soils. 



