MAGNESIA I.MPRKGXATK]) SOILS. 178 



Culture exi)eriuipnts with rye, maize and kidney beans 

 were reported by lieruardiiii and Corso* in 19()8. The nutiient 

 solution contained the ratios of lime to magnesia (magnesia 

 as 1), 8, 2, 1, ^ and J. Eye gave tlie best results in the solution 

 in whicdi the relation of lime to magnesia equalled 1 and better 

 results with the higher proportion than the lower; maize gave 

 the best results with the proportion of lime to magnesia equal 

 to 2 and better wifli the higher than the lower, showing that 

 an excess of lime does less harm than an excess of magnesia. 



From the results of experiments with oats, beans, rice 

 and millet, Asot in 1909 confirmed the obserTation thai a. 

 certain favourable ratio of lime to magnesia exists for })hnit 

 growth. 



This review of the work which has been done Avith reg;u(l 

 to the mflueivce of the lijne-magnesia ratio upon plant growth 

 is admittedly incomplete, but sufficient data have been given 

 to show tliat the best development of a plant dejiends, other 

 things being equal, u]jon a certain ratio of tlie amounts of 

 lime and magnesia available for absorption, by plants. For 

 cultivated ])lants, the oi)timum ratio varies between one i)art 

 of lime (CaU) to one part of magnesia (MgO) and seven parts 

 of lime to one part of mag)iesia, according to the variety of 

 plant; in general, tlie lime must exceed the n)agnesia in 

 amount. 



In the soil, the relations of the lime and magnesia to i)lant 

 growth are not so simple, because it is impossibh^ to determine 

 the actual quantities of lime and magnesia available for 

 absorption by the plant, oAving mainly to the absor])tive 

 l)roperties of the soil by Avhich they remove the b;ises from 

 solution and hold them in a someAvhat difficultly soluble form. 



h^or the determination of the available amounts of lime 

 and magnesia in the soil, KatayamaJ in 1902 (daimed ihat the 

 extraction of the fine earth < 025 mm. Avith 10 per cent, 

 hydiocdiloric; acid afforded reliable information as to the 

 relatiA^e amounts of lime and magnesia available for absorption 

 by plants. This method has only recently come to my notice, 

 and Ave have not had an opportunity of testing its accuracy in 

 the case of the soils of the Great D^-ke. 



In an endeavour to obtain a measure of the amounts of 

 lime and magnesia Avhich are available for a])sorption by 

 plants in the Dyke soils, I ado])ted Dyer's method tised for 

 the determination of available ])hosphoiic oxide and potash 

 in soils, Anz., extraction of the fine earth < 3 mm. Avith 

 1 per cent, citric acid solution at tlie ordinary tem])erature for 

 one week. 



* Bernardini ;uul Corso : "Concerning the influence ol' various 

 relations between h'me and map;ne.sia on the development of plants." 

 Staz. Sper. A^r. Ital.. 41, 191-208. 



t Aso : " On the influence of the ratio of lime to magnesia upon the 

 yield in sand culture." Tokyo Imp Univ., Agric. Col. Journ., 1, 175-180. 



+ Katayama : "On the determination of the available amounts of 

 lime and magnesia in the soil." Bui.. Agric. Col. Univ. of Tokyo, vol. vi. 



