758 EXPERIMENT STATION EECORD. 



aiifl alumina and to those containing no phosphate were also added 10 gm. calcium 

 snlphate. . . . 



"The experiments were continued through 3 periods. In the lirst period the bar. 

 ley matured its heads and many of the pea pods were well iilled. The second period 

 extended through the shortest days of the winter, when the lack of sun and the lower 

 temperature were unfavorable to the best development of the corn and tomatoes. 

 The third period was made shorter than the others, and none of the plants reached 

 their lull development." 



The data, whicli are given iu tables and diagrams, are thus sum- 

 marized : 



"(1) All the plants receiving the phosphate of irou and alumina show a gain over 

 those receiving no phosphate. This effect was most marked with the corn, the yield 

 being 3 times as great as where no phosphate was used. The weight of the tomato 

 plants was doubled. The turuips and ruta-bagas responded vigorously, the crop of 

 roots being doubled. On tlie other hand, the peas and potatoes gained luit little. 



" (2) All the plants receiving the insoluble Florida rock show a gain over those to 

 which no phosjiate was given, the crops of clover, ruta-bagas, corn, tomatoes, and 

 ruta-baga roots being more than doubled. The barley, potatoes, and especially the 

 potato tubers, gained but little. All the plants showed a gain over those receiving 

 the phosphate of iron and alumina except in the case of the barley, corn, turnip 

 roots, and potato tul)ers. 



"(3) AH the plants were benefited by the addition of the acid rock. The barley 

 and corn show the most marked increase, the yield being double that from the crude 

 rock. Tlie ruta-bagas and the turnips derived nearly as much benefit from the crude 

 rock as from the acid roclv. 



"The effect of the acid rock was very marked with all the plants grown, those 

 receiving it in nearly all cases at once taking the lead and keeping it to the end. 

 The plants were darker green in color, and the tubercles, which were developed on 

 the roots of nearly all the leguminous plants, were larger and much more numerous. 

 It was noticeable, however, that in some cases, especially with the clover, turnips, 

 and rutabagas, the good eft'ects of the acid rock were more marked during the first 

 few weeks of growth than at a later stage, when the roots had become more fully 

 developed and had begun to forage for themselves. It would ai)pear that the young 

 plants feed but little upon the insoluble phosphates; but that the organic acids 

 present in the sap of the roots exert a solvent action upon the insoluble phosphates 

 in the soil, gradually converting them into available forms." 



The results indicate that although the soluble phosphoric acid was 

 the most available the iusolu))le forms were used to a considerable 

 though varying extent by the different plants. The solubility in ammo- 

 nium citrate was not a true measure of the availability of the phos- 

 phoric acid to the i)lants. "The ability to appropriate water-insoluble 

 phosphoric acid appeared with some species of plants to greatly 

 increase as the plants developed." 



The fertilizing eflFect of the nitrogen of different green manuring 

 plants, M. Maercker {Jahrh. agr. ehem. Vers. Stat. HaUe, 1895, pp. 

 40, 41). — Equal amounts (1.5 gm.) of nitrogen in the form of nitrate of 

 soda, Lathyrus sylvestris icagneri, alfalfa, red clover, and esparcet were 

 applied to white mustard grown in pots on sandy soil. The effective- 

 ness of the green manures was in the order given above and appeared 



