708 



EXPERIMENT STATION RECORD. 



reported, illustrating especially the difference in the relation of legumi- 

 nous plants and cereals toward nitrogen. It appears from these experi- 

 ments that potash and phosphoric acid were without effect on oats 

 except when used in connection with nitrogen. On the other hand, 

 they exerted their full effect on the peas and vetches without the addi- 

 tion of nitrogen. The yields on the pots under different methods of 

 fertilizing were as follows: 



Yields of oats, peas, and retches with different fertilizers. 



The oats grown on the unfertilized soil and on the soil fertilized only 

 with potash and phosphoric acid contained on the average 0.23 gm. of 

 nitrogen per pot; while the peas grown on the unfertilized pot contained 

 2.02 gm. of nitrogen, and on the pot fertilized with potash and phos- 

 phoric acid 6.11 gm. of nitrogen. The results plainly show that potash 

 and phosphoric acid were without effect on cereals except when a su])- 

 ply of soluble nitrogen was present in the soil or was furnished in the 

 fertihzer, but that they were effective on leguminous plants when the 

 nitrogen was deficient, because these plants assimilate the nitrogen of 

 the air. 



From these experiments it appears that for each 100 kg. of phosphoric 

 acid which the soil or the fertilizer furnishes to vetches 400 kg. of 

 atmospheric nitrogen is collected and stored up in the plant tissue; 

 while for each' 100 kg. of phosphoric acid furnished to oats 250 kg. of 

 nitrogen is drawn from the soil or the fertilizer applied. 



In order that leguminous plants may collect the maximum amount 

 of nitrogen from the air they must be liberally fertilized with jihos- 

 phoric acid (and, where necessary, with potash). This should be applied 

 when the stabble is turned down and the leguminous crop seeded, or 

 if the latter is seeded among the grain sufiBcient phospate should be 

 applied to supply the needs of both crops. In no case should the legu- 

 minous crop be allowed to hunger for phosphoric acid. The quicker 

 its needs in this respect are supplied the sooner and more rapidly it 

 will collect nitrogen from the air. 



The results of investigations of the cause of failures of alfalfa in cer- 

 tain fields of Laubenheim, on the Rhine, are cited as indicating that 

 decline in thriftiness of leguminous plants on soils on which they have 

 been grown continuously for several years may be due to exhaustion 

 of the soil in available phosphoric acid. 



