686 



TEE AOEiOULTURAL JOURNAL. 



ordinary manure heap ; when thoroughly 

 rotten there is a considerable formation 

 of saltpetre, which is one of ihe most 

 valuable constituents of such manures. 



Nitrate op Soda. 



Owing to its use in the manufacture of 

 gunpowder, nitrate of potash h'ss a some- 

 what artificial value, and its place as a 

 manure is taken by nitrate of soda, which 

 is found naturally existing in South 

 America, whence it derives the name of 

 Chili saltpetre. It is excessively soluble, 

 and apt to absorb moisture if left in a 

 damp place, and being in a state ready for 

 assimilation by plants, it is perhaps the 

 quickest acting of all manures. It may 

 be applied to all crops which need nitro- 

 genous manuring, but its effect is, as it 

 were, to stimulate the appetite of the 

 plant, and unless there is a supply of 

 other forms of plant food available, the 

 hungry plant is rather damaged than 

 assisted. It should, therefore, only be 

 used in conjunction with other fertilisei-p, 

 at any rate with ].hospliates, and is best 

 put on after the crop is np, as it is so easily 

 washed beyond the reach of the roots. In 

 fact, the safest plan is to apply the amount 

 to be used in two or three light dressings 

 with an interval between, or, as we say, 

 in fractional top-dressings. It must not 

 be mixed with superphosphate or any 

 manure having superphosphate for a basis, 

 as there will be a loss of nitrogen through 

 the action of the acid in these manures. 

 As a general rule, a good sample should 

 contain about 15| per cent, of nitrogen, 

 the usual standard being 15-65 per cent, 

 corresponding to a purity of 95 per cent. 



Nitrogenous Manures. 



The farmer has often to ask himself 

 whether a given crop should receive a 

 dressing of nitrogenous manure or not ; 

 all that can be done here is to indicate the 

 principles that should guide his decision. 

 In the hrst place he must conbider his 

 crop, secondly his laud, and thirdly the 

 kind of manure to use. As to the crop, 

 all cereals require a good supply of nitro- 

 gen, root crops pcrha])s rather less, while 

 leguminous plants, which will be spoken 

 of farther on, can practically do without 

 any artificial aid in this direction. Pota- 

 toes, which are gross feeders, should 

 always receive a dressing. But some soils 



are better supplied with nitrogen natur- 

 ally than others ; rich vegetable soils and 

 loams containing a good proportion of de- 

 caying vegetable matter can often supply 

 sufficient for the needs of a crop, while 

 sandy soils often need it badly. Further- 

 more, it is plain that as animal or vege- 

 table substances have first to decay with 

 the formation of ammonia, and this has 

 to be changed into nitrates, while am- 

 monium salts have but one conversion to 

 undergo and nitrates none at all, nitro- 

 genous manures do not all act with the 

 same rapidity. Such manures as sewage, 

 blood, etc., act only gradually, giving a 

 slow supply of plant food for a consider- 

 able period ; while, on the other hand, it 

 is quite possible for the effect of a dress- 

 ino- of nitrate of soda to be visible a day 

 01° two after application Of the purely 

 chemical fertilisers, sulphate of ammonia 

 and nitrate of soda, the former would be 

 preferred in a wet season, the latter in a 

 dry one, for obvious reasons. There 

 seems, on the whole, little difference be- 

 tween their actual manurial effect on the 



crop. „ 



In this connection, the system ot green 

 manuring with leguminous plants may bfi 

 noticed. The legumes are an order of 

 plants of which beans, peas, the clovers, 

 lucerne, and vetches may be taken as 

 examples ; and their roots form the home 

 of a species of microbe which has the con- 

 venient power of absorbing nitrogen from 

 the air and supplying it to the plant. If 

 then a crop of one of tbese varieties be 

 grown, it will contain a store of nitrogen 

 which has cost the farmer nothing ; and 

 if the crop be ploughed under, it will 

 enrich the soil to a far greater extent than 

 if some other kind of plant had been used, 

 and the usual loss of nitrogen will be 

 made up in the cheapest manner. It 

 sometimes happens that the soil is free 

 from the germs of these bacteria ; in this 

 case the absorption of nitrogen does not 

 take place, but it has been found possible 

 to inoculate the soil, so to speak, with the 

 proper germs, and then the process goes 

 on in full force. 



Questions. 



1. Sliow that chemical compounds often 

 differ greatly from the elements that com- 

 pose them. 



2. Give instances where microbes are 

 useful to the farmer. 



