IRISH GARDENING. 



(C 



IRISH GARDENING. 



an illustrated monthly. 

 Offices-53 Upper Sackville Street. Dublin. 



Subscription. — 3/- per annum, post Irce. 



Editorial.— All Editorial CnmmunicationB, copy, and pholoeraplif 

 should be a.klressed to "The Editor." 



Business Communications. — All letters regarding Subscriptions, 

 Ad\ertisenients. and oiher business matters must be addressed Icj 

 -The Manager." 



Soil Hygiene 



LAST month, when writing upon the subject 

 of artificial manures for garden soils, we 

 referred to certain possible ill results 

 arising from the excessive use of farmyard 

 manure. Let us briefly review some of the facts 

 bearing upon this matter. We all know that 

 farmyard manure when fresh is not only useless 

 as a food for cultivated plants, but that to the 

 roots of many it acts harmfully, even to the 

 extent of being actually poisonous. Before the 

 dung is safe to use and fit to absorb it must 

 become " ripe " — that is, reduced to a well-rotted 

 condition. What is the meaning of this change ? 

 .\ mass of farmyard manure is made up of a 

 mixture of fermentable organic matter, the 

 various constituents of which are of too complex 

 a nature to be directly used by plants. Indeed 

 they represent for the most part substances 

 manufactured by plants themselves, and before 

 they can be re-used by fresh crops the}- must be 

 broken down to the simpler compounds out of 

 which they were originally built up. Now, this 

 importfuit work is invariably carried out in 

 nature by different kinds of bacteria, a class of 

 fungi representing the very smallest forms of 

 life known to science. It is these bacteria that 

 feeding, growing, and multiplying in the 

 manure cause it to ferment, and the heat that is 

 generated and the changes that take place 

 during the process are simply the outward and 

 manifest signs of the vital activities operating 

 within the heap. 



During the process of fermentation much of 

 the insoluble organic matter becomes soluble, 

 and various kinds of acids and gases are formed 

 that would be detrimental to the roots of many 

 garden plants if the process took place in the 

 soil. As the fermentation proceeds the soluble 

 organic matter is destroyed, and the acids 

 neutralised, and until this stage is reached or 

 nearly so it is scarcely safe for gardeners to 



use the manure unless for the grosser-feeding 

 crops. When the rapid fermentation is over 

 and the manure gradually passes into a milder 

 and safer condition, it still contains a consider- 

 able amount of fermentable organic material, 

 but the fermentation proceeds at a very much 

 slower pace. When applied to the soil it adds 

 to the stock of humus already present there, 

 while its fermentation is now carried on by the 

 vast bacterial population that inhabits the 

 whole depth of surface soil even to its minutest 

 particle. This humus contains rich stores of 

 food, but stores that are unavailable to crops 

 until the bacteria break up the compounds and 

 reduce them to simpler bodies — an operation 

 often taking long years for its completion. How 

 much of this valuable food material during any 

 particular season's growing can be released for 

 the use of crops, or whether they can get any 

 of it at all, depends entirely upon the activity of 

 these particular races of bacteria. They regulate 

 this source of soil fertility absolutely. This 

 being so we can easily understand how import- 

 ant it is for a gardener to clearly understand 

 the main factors that help or hinder the activity 

 of these beneficial germs in the soil. 



One of the most helpful thing in this con- 

 nection is air, as the change produced in the 

 manure is essentially a process of oxidation 

 carried on by living bacteria ; therefore drainage 

 and thorough cultivation, so as to admit abund- 

 ance of air to the soil, are of first importance. 

 But as we have already seen, certain acids are 

 included among the first products of decom- 

 position, and these are alike hurtful to delicate 

 roots and to the bacteria themselves. If they 

 are allowed to accumulate the soil gets sour, the 

 useful fermentations are checked, and the crop 

 fails to reach its highest yield. 



To prevent acidity in such cases lime should 

 be freely applied ; this will neutralise the acids 

 and render the soil sweet and wholesome. 

 By freeing the bacteria of their harmful excreta it 

 will promote further and more rapid fermentation 

 of the humus, and therefore a quicker liberation 

 of plant food. Soil acidily is undesirable for 

 other reasons, one of which is that the club-root 

 fungus that attacks Brassica with such disastrous 

 results is much encouraged by an acid condition 

 of soil and considerably checked by a neutral 

 or a slightly alkaline one. Heavih- manured 

 garden soils lacking in lime are particularly 

 liable to invasion by this pest. The only effective 



