6o 



IRISH GARDENING 



la Ihr .•>v|.i-lillU-Mt li-f.TIV(l U. hf IlliUlr U). a soil 



(i>m|.(>sed (if plant asln-s and sand wliitli had 

 hi'i-n washed iit-rfcttly tU>an. IManl- ashi->. it 

 nHKlit 111' statfd. iU'i- fn-c fruni (•(imiMnnuls ut 

 iiitro^'iMi. hut aiv othfi'w isc rich in the niim ral 

 tixxl ic(|uiri"(l Ity jdants. Jlavinii niaclc n]i lu-' 

 |i..tluls of tht," ndxtuif he stiwcd a knuwii 

 weight of sonii- ]iart inilar seed (Sunlloucr 

 lor fxami.li-) in .arh. To on.. |M.t ii.' iuhU-d 

 IM.tassinni nitrate, and to tlie otiu-r iiotassiuiu 

 earhonate. lie also niaih- up a contnd ]»<d with 

 sand alone, and tlnallv compared tlie drv weiirht 

 of the crop in the three pots with the weight of 

 tiir seed in each ease. 



The result for Sunflower is seen in tlie lal.l.^ 

 the weight of seed, lieing regarded as unity, the 

 minihers repretiunt the weiglit of the erop : 



I'ure S.tnd 



:i.o 



4.ti 



Sand + Ash 

 + Potassiui 

 Niti-ate 



198.0 



Oats, barley. gra.sses. peas, heans. ciovei'. \r., 

 were experimented with in the same way. .iiid 

 (•((ually striking results were ohtainid. iu ever_\ 

 case wit hout exception. 



The experiment showed clearly that once the 

 sl.ire of nitrogen in the seed is consumed, a jdaiit 

 jnakes no further growth in th.- jihsence of coin- 

 hined nitrogen in the soil. Air. with its SO j)er 

 cent, of free nitrogen, is of no avail. As a result 

 of his researches extending over several years. 

 Houssingault was led. to tlio conclusion that 

 jilants obtained their nitrogen from the s<jil alone, 

 and. only in the forn\ of nitrates. 



Tlu- jtresence of ni- 

 trates in the soil, there- 

 lore, as well as the mode 

 of their formation and. 

 the agencies at work 

 tending to re])air their 

 loss, became a matter 

 of the greatest im])ort- 

 a nc e, and to t h i s 

 (juestion Bou.ssingault 

 next turned liis atten- 

 tion. It had been 

 shown })y Cavendisli 

 a b o u t a e e n t u r > 

 jireviously that nitric 

 acid is formed wlien 

 the air is electrically 

 sparked, the oxygeii 

 and nitrogen being 

 thereby united, to form 

 t h e acid- in the 

 lightning we see; the 

 electric spark re])ro- 

 duced. in th<- grand 

 scale. Boussingault 



set himself to lind out 

 if the lightning also 

 forms nitric acid, and 

 for this purpose he 

 tested the rain-water 

 which fell during 

 thunderstorms. His 

 tests revealed the 

 presence of nitric acid , 



An Ixgeniovs Device for Firming I^ekdlixg Trees 

 (sec page (32). 



showing that ow^rn ;ind nitrogen are combined 

 in the lightning track : the acid being carried by 

 the lain to the soil, aiul there coming in contact 

 with lime, i.otash. .ind, such minerals, the all- 



import.mt niti-ates arc ton I. Here anf 



natural j.iocess. ;it .iiin t.ite. was I'evealed. 

 wln'r.'b\ the nidou'en .it t h.^ air i^ .■.uubined 

 .111,1, 111., slock of nitrali.s in tli-' ^..il .•i.l.,l,.'d. to 

 Ir.iiii lini.' 1.1 tim.'. 



Liebig's work with [■.■-ai-.l, t,. .arb.m assimila- 

 tion has been refen.-.l. \i< \'i previ lus article. 

 .Vs might lie expected,, t 111- i|ii.slion of nit I'ogen 

 assimilation also enuage.i his attention, though 

 h.. di.l n.d investigate the matter as thoroughlv 

 as Houssiiirault. whose researches were of a 

 .somewhat later dat.^. l.iebiu: .ipproached tli.- 

 subj.-ct bv studying the linal pioducts of decav 

 .if v.'getable and. .iiiim.il matter, (iiven time 

 ami. pl.'uty of air. a plant <in decaying (lisap- 

 p.'ars ;is completelv as if consumed bv lire. 

 th.' ;ish ..r min.-ral n"ia1t:-r onlv r.'mainimz." -Non.' 

 ..!■ th.' nitr..g.'n r.Miiains in tlie .■ish when ;i ].l;in1 

 is biiMil. iH'itii.'i- (l.oi'S an\ r.'main w ln'ii a plan! 

 decays in tlu' ojieu ail', iu the latter ca.sc it 

 passes away into the air in the form of am- 

 monia, ,iust as the cai-bon passes away in the 

 carl)onic acid, gas. Conversely. Liebig held. 

 a iilant obtains its nitrogen froni ammonia ami, 

 11. i1 li-..m th.' free nitrog<-n of the air. Ittli.' 

 ammonia is present in the air the plant mav 

 abs..rb it by means of its leaves : but bir the 

 m.ist part the jilant obtains the ammonia, from 

 th.- soil, as the gas. owing to its .s.dubility. is 

 .piickly washed, out of the air. When oi-ganic 

 matt:-!-, such as fai'mvard, manure. (U'cav.s, 

 incorp. , rated, in th.> s.iil. tli.' -ras in that cas.- 

 d.M's not .'s.-ap.' into th.' air. but b.rms c.'rtain 

 jimmonia com|)ound,s in the soil which .serve 

 till' ])lant equally well. 



Liebig and Boussingault were both, therefore, 

 o])posed, to the theory 

 1 liat plants were able 

 t.i assimilate the free 

 nitrogen of the aii-. 

 It was incom])atible 

 with the ]iractice of 

 am-icult ui'c. It was 

 ..mti'ary to the results 

 of laboratory exjieri- 

 nu'nts, and was in fact 

 unsui)])orted as far as 

 they knew by any 

 direct evidence. Never- 

 theless, the whole con- 

 troversy was renewed 

 lalei' .m in an acute 

 form. If the theory 

 was to be abandoned < 

 there were certain facts 

 that called aloucl for 

 explanation. How, for 

 instance, could the im- 

 portance of clover in a 

 rotation be explaiiu-d. 

 an im[)orlance long re- 

 • ognised by the jiracti- 

 .al agri<!ulturist. not 

 lor the feeding value of 

 1 he croii ijalone, but 

 for the renuirkable way 

 in which it enriched the 

 ground for the suc- 

 leeding grain crop. 

 {To be continued.) 



