IRISH GARDENING 



VOLUME V. 

 No. 52 



A MONTHLY JOURNAL DEVOTED TO THE 



ADVANCEMENT OF HORTICULTURE AND 



ARBORICULTURE IN IRELAND 



JUNE 

 igio 



Bacteria in Relation to Crops 



I. AMMONIFICATION 



,OIL is the original 

 source from which our 

 crops obtain most of 

 their food. With the 

 exception of carbon, 

 which is extracted by 

 the leaves from the 

 carbonic acid g-as of 

 the air, everything- 

 else is absorbed by the 

 roots from the soil. 

 It is well understood 

 by all practical g^ardeners that the fertility of 

 the soil almost wholly depends upon the stock 

 of suitable nitrog-en, phosphorus, or potassic 

 compounds that are present in the soil. But it 

 is not merely necessary that these substances 

 should be there, as that alone may mean very 

 little to the wants of the crop. The food stuflfs 

 must be there in a form in which the roots can 

 absorb them. The needful compounds must be 

 soluble in water. But soluble compounds are 

 difficult to retain in the soil ; they are very liable 

 to escape in the drainage water. The most 

 difficult of all to retain are the nitrates, and there- 

 fore the fertility of a soil often depends upon 

 the amount of its available nitrog^en. To make 

 our points clear to non-chemical readers let us 

 dig-ress for a moment in order to explain that 

 Tiiirogcn in a free or uncombined state exists in 

 the air to the extent of three-quarters of its 

 volume. But in this free or uncombined condition 

 it is useless to crops. Nitrog^en forms one of 

 the necessary constituents of ammonia, and 

 ammonia readily unites with acids to form salts 



ot ammonia. Another compound of nitrogen is 

 nitrate — such as nitrate of soda, nitrate of 

 potash, or nitrate of lime. Salts of ammonia 

 and nitrates can be used by crops as suppliers 

 of nitrogen. The highest or most complex 

 nitrogen compound is albiim.en or protein, but 

 this can only be produced within the body 

 of a plant, and under the influence of life, 

 and it is to enable plants to manufacture this 

 most essential of all foods that they require 

 to be supplied with either nitrates or salts of 

 ammonia. 



To return to our main subject. The sources 

 of nitrogen loss to the soil are mainly but not 

 entirely due to the nitrogen in the form ^c^i. albu- 

 men, &c., removed in the crops, and to nitrates 

 lost by drainage. What are the sources of the 

 soil's gain in nitrogen ? The residues of crops, 

 farmyard manure, or artificial manures contain- 

 ing nitrogen— such as nitrate of soda or sul- 

 phate of ammonia. The two latter com- 

 pounds, being readily soluble in water, can be 

 taken up by the roots immediately they are 

 applied to the soil. It is exactly because these 

 fertilisers are so soluble that they should be 

 added in relatively small quantities, as other- 

 wise they form too strong solutions for the 

 delicate root-hairs. But what about the residue 

 of crops and farmyard manure, the nitrogen of 

 which is in the form of protein ? Protein as it 

 exists is useless to the crop ; the roots cannot 

 take it in. Before they can do so the protein 

 must be broken down into simpler compounds, 

 and it is a well ascertained fact that they are so 

 broken down in the soil, and one of the decay 



