GARDEN 3IANUEES. 



468 



they bring about in the physical state of the soil — the state just indicated 

 as being so desirable. The plant food contained in these organic manures 

 is, for the most part, unavailable, although m time it becomes available. 

 The immense importance of the physical properties of farmyard manure 

 and similar substances is such that we cannot fairly compare them with 

 chemical fertilisers. 



Another substance which largely alters the texture of soil, and which 

 there is a tendency in the present day to neglect, is lime. This sub- 

 stance, whether used as quicklime, slaked, or the more common, because 

 naturally occurring, carbonate, as chalk or limestone, is most essential. 

 A continual leaking away of this as soluble bicarbonate and as 

 nitrate has ever occurred, but never to such an extent as now, when so 

 many chemical manures are used. By way of illustration we may note 

 that every particle of ammonium- sulphate requires a particle of lime to 

 combine with the contained acid, and yet another to unite with the nitric 

 acid which is formed. Most of the unused nitrate formed by the de- 

 composition of organic matter (humus) in the soil also passes away as 

 nitrate of lime. Similarly, superphosphate requires a great deal of lime. 

 That the acidity of soil, due to lack of carbonate of lime, is frequently 

 the cause of many failures in pot cuUitrc and borders, there is abundant 

 evidence to show. Nor is this to be wondered at if we reflect that old rotten 

 turves and other ingredients of potting earth, admirable though they be 

 otherwise, are commonly deficient in carbonate of lime. Lime in some 

 form, preferably a small quantity of quicklime, intermixed thoroughly 

 with potting earth some time before using, often works wonders. Basic 

 slag usually answers the same purpose, and generally is better, because 

 of the phosphate which it contains. 



It is not proposed to discuss, or even enumerate, the various chemical 

 fertilisers available. Particulars are readily accessible to all interested. 

 The merits of the various mixtures must be judged by each individual. 

 Let the cultivator understand that although about ten chemical elements 

 in suitable forms are essential for all plants it is seldom necessary to 

 trouble about more than three or four of them, because the others are 

 practically ahvays present in sufficient quantities. Given a soil which is 

 in fau^ condition, it is usually not necessary to trouble about special 

 fertilisers other than those containing suitable nitrogenous, phosphatic, 

 and occasionally potassic compounds. Of these, phosphates and potass 

 are retained by nearly all soils, the only danger being the changes to very 

 inert forms. But the nitrogenous will be largely changed from one form 

 to another, in natural sequence, until the nitrate form is reached, when it 

 is available for plants, but very liable to loss in drainage. It has been 

 said that he will be the most successful cultivator, all other things being 

 equal, who always has sufficient nitrate for his plants and 7W)ie to spare. 

 This condition can be largely obtained by observing the colour of foliage,, 

 abnormally dark green denoting abundant, and a light green deficient, 

 available nitrate. Of course, other things often cause the latter appeai*ance. 

 In houses the matter is much more under control than in garden or field, 

 because we may very profitably use the valuable (horticulturally and 

 commercially) nitrate of potash (saltpetre) in small quantities. This 

 might with great advantage be used much more frequently, especially for 



