Scientific Agriculture. 



340 



[April 1908. 



goes little change from the mixing. Evi- 

 dently the reaction between the slaked 

 lime from the cyanamide and the soluble 

 phosphate gives rise to di-calcium phos- 

 phate, the usual precipitated or 

 " reverted " phosphate which is com- 

 pletely soluble in citric acid solution. 

 Very little change to tricalcium phos- 

 phate is brought about either by lime 

 or the heating. 



From the fertiliser point of view, then, 

 the mixture of cyanamide with super- 

 phosphate occasions no loss of nitrogen, 

 but more or less of the phosphoric acid 

 ceases to be water soluble, remaining, 

 however, as the readily available di- 

 calcium phosphate. While the precipi- 

 tated phosphate cannot be regarded as 

 of quite the same value as water soluble 

 phosphate, the falling-off in fertilising 

 value is slight. 



Various attempts were made to ascer- 

 tain how much of the nitrogen of the 

 original cyanamide had been converted 

 into ammonium salts in the mixed 

 manures ; the results were, however, 

 unsatisfactory owing to the fact that 

 the unchanged cyanamide is itself con- 

 tinuously decomposed when distilled 

 with magnesia. They indicated, how- 

 ever, that little formation of ammonium 

 salts had taken place. 



Some experiments were also made to 

 see if any quantity of the dicyano- 

 damide, which is said to be poisonous to 

 plants, had been produced in the mix- 

 ture. Six pots were made up, each con- 

 taining about 3 kilos, of sand, and, in 

 addition to potassium sulphate and other 

 nutrient salts, 0"3,3 and 6 grams respect- 

 ively of mixture No. 3 were added to the 

 pots with an appropriate amount of 

 water, and young barley plants were 

 planted in each pot. The experiment 

 was started too late in the year to be 

 pushed to a conclusion, but in all cases 

 the barley grew, though not very freely 

 where 6 grams (=0*2 per cent- of the 

 whole contents of the pot) had been 

 added. However, such an amount is 

 excessive in a sand culture, and the mere 

 fact that the barley grew for three 

 months in contact with so large a pro- 

 portion is evidence that nothing that 

 would be poisonous to plant life in prac- 

 tice had been formed in the mixture. 



From our experience in making up 

 these mixtures I should be strongly 

 inclined to recommend farmers using 

 cyanamide to mix it before sowing ; it 

 will mostly require to be used with a 

 phosphate, and it is much less trouble to 

 mix cyanamide with superphosphate in 

 a manure shed than to deal with it in 

 the open. It would be practically im- 

 possible to sow cyanamide by hand, and 

 even a machine would result in great 

 waste and unpleasantness to the men 

 except on the stillest of days ; but after 

 the first spreading of the cyanamide on 

 the floor is over, mixing with superphos- 

 phate presents no further inconveni- 

 ences, and the resulting mixture is easy 

 to handle and can be dealt with like any 

 other artificial manure without even the 

 waiting period before seeding that is 

 recommended when cyanamide is sown 

 alone. 



The net conclusions from the above 

 experiments are that calcium cyanamide 

 as now manufactured can be stored for 

 a reasonale time under ordinary condi- 

 tions without danger or sensible loss 

 of its fertilising properties ; cyanamide 

 can also be mixed without difficulty or 

 loss with superphosphate, the resulting 

 mixture being as easily handled as any 

 other artificial manure. — Journal of the 

 Board oj Agriculture, Vol. XIV, No. 11, 

 February, 1908. 



[Experiments wibh this new fertiliser, 

 which is already stocked by at least two 

 firms in Ceylon, are now in progress. —Ed,] 



SOIL CHEMISTRY. 



A good deal of improvement work is 

 being done in tnis line in America. Re- 

 cent investigations by Osterhout and 

 others (of Bot. Gazette, 45, February, 

 1908, p. 117) go to show that "magnesium 

 salts and potassium salts, used separ- 

 ately, are poisonous to plants, but when 

 mixed together (in suitable proportions) 

 the poisonous effects more or less com- 

 pletely disappear." It is to be noted 

 that these poisonous effects only show 

 markedly when the solutions are com- 

 paratively concentrated, and that both 

 potassium and magnesium are essential 

 constituents of the food of plants, 



