210 



THE FARM:ER'S magazine. 



ON THE ACTION OF SALTPETRE EMPLOYED AS A MANURE. 



[translated from the FRENCH OF THE " JOURNAL d'AGRICULTURE PRATIQUE."] 



In a series of iavestigations, the results of which I 

 have presented to the Academy, I have shown what is 

 the influence of nitrates associated with phosphates upon 

 the development of vegetable organization, and, con« 

 sequently, upon the assimilation of carbon by the 

 leaves. In every case, helianthuses, on reaching efflor- 

 escence, have weigned just so much more in proportion 

 as the saltpetre put into the soil has been stronger. 



The precision with which I have been enabled to dose 

 the nitric acid, by means of the tincture of indigo, de- 

 cided me to extend my observations, in order to deter- 

 mine more strictly than I had done, the nitrate absorbed 

 by the plant, and that retained by the soil, whether 

 naturally or modified. 



The helianthuses were cultivated in a white quartzose 

 sand with small round grains, with which, in order to 

 favour the access of air, we had besides mixed large 

 fragments of quartz. The soil, and the earthen pot 

 which contained it, were washed with abundance of 

 water, to remove entirely the saline substances, and 

 then calcined to a red heat. 



The grains gathered and analyzed in 1857 contained 

 2.87 per cent, of azote. First experiment, helianthus 

 under the influence of gr. 0.08 of nitrate of potash. 

 The soil was formed of— 



Grammes. 

 Quartzose sand ., .. .. 400.00 



Fragments of quartz . . .. .. 100.00 



Phosphate of Hme .. .. .. 1.00 



Nitrate 08 



The pot weighed 214.00 



Total 



715.08 



The vegetation was conducted in the open air, but shel- 

 tered from the rain. The soil was watered with distilled 

 water, exempt from ammonia, and containing about 

 one-third of its volume of carbonic acid gas. 



On the 22ud of June we planted two grains, weighing 

 together gr. 0.116, before containing 0.0033 of azote. 



On the 15th July the helianthuses had each four leaves 

 formed and two buds. The cotyledons were withered. 



The 10th of August: The plants have followed the ordi- 

 nary development ; the oldest leaves have faded as the 

 new ones appeared. We have never counted more than 

 four leaves intact. 



The 20th of September : The two helianthuses bear 

 twenty-three leaves : those at the base of the plants 

 are faded. Each plant has a flower, of a fine yellow, 

 the corolla of which does not exceed a centimetre in 

 diameter. The thickness of the stalks is three milli- 

 metres ; the heights twenty-six and thirty- three centi- 

 metres. 



The roots were perfectly healthy, and were easily 

 taken up. The plants dried in a stove weighed gr. 1.168. 

 Analyzed by a single operation, they yielded gr. 0.0102 

 of azote, 



DOSE OF NITRATE REMAINING IN THE SOIL. 



The water in which the sand and the pot reduced to 

 powder were put in digestion remained colourless. In 

 this water we put a dose of 0,0107 of nitric acid, equi- 

 valent in azote to 0.0028. 



THE EXPERIMENT CONTINUED. 

 Gr. 



In the grains, azote 0.0033 



la O.OS of nitrate 0.0111 



Gr. 



Azote introduced 



0.0144 0.0144 



la the plants, azote 0.0102 



la.the soil in the state of nitrate 0.0028 



Azote found 0.0130 



Difference. . . . 



0.0130 

 0.0014 



KITRATE ABSORBED BY THE PLANTS, AND NITRATE 

 REMAINING IN THE SOIL. 



The 0.0107 of nitric acid found in the soil represents 



Nitrate of potash 0.0204 



Nitrate of potash introduced ... 0,0800 



Difference 0.0596 



Of which the equivalent ia azote is 0.0083 



If the nitrate expressed by the difference 0.0596 had 

 been absorbed, the helianthuses would have fixed the 

 0.0083 of azote belonging to that salt ; but this has not 

 been the case. In fact, 



Gr. 



The plants contained azote 0.0102 



Deducting the azote of the grains 0.0033 



There remains 0.0069 



for the azote acquired by the helianthuses attributable 

 to the nitrate absorbed, and not 0.0083. 



The soil, therefore, ought to have had in it the ni- 

 trate not assimilated by the plants, but which was not 

 found in it. It is very probably the nitrate trans- 

 formed into carbonate ot potash, the azote of which has 

 not been fixed definitively by the plants. We have 

 stated plainly that the water in which the soil was put in 

 digestion was weakly alkaline. 



DOSAGE OF POTASH IN THE SOIL. 



We have found in the water into which the soil and 

 the pulverized flower-pot were put in digestion, 0.007 

 of potash, which could have no other origin than the 

 nitrate of potash, because of the washing to which all 

 the earthy matters were subjected. 0.007 of alkali 

 would take 0.0080 of nitric acid to constitute 0.0150 of 

 nitrate, which belonging to the soil, ought to be added 

 to the salt directly dosed. 



NITRATE OF POTASH ABSORBED BY THE PLANTS. 



Gr. 

 Nitrate corresponding with the potash found \ 



in the soil J 



Nitrate found in the soil 0.0200 



0.0150 



The uitrate of potash non-absorbed 0.0350 



Nitrate introduced into the soil 0.0800 



Nitrate absorbed by the plants 0.0450 



The equivalent of which in azote is 



The azote fixed by the helianthus attributable \ 

 to the nitrate being J 



It will be seen that these two numbers differ only to 

 the extent of 7-lOths of milligramme. 



