1 Aprrn, 1902.] QUEENSLAND AGRICULTURAL JOURNAL. 235 
As regards the loss of the important and expensive fertilising constituent, 
nitrogen, however, the case is very different. The soil appears to have very 
little affinity for the forms of this element so extensively used in fertilisers— 
nitrate of soda and sulphate of ammonia—and if they are not quickly taken 
up by the cro» they are likely to be lost in the drainage water. Moreover, 
the insoluble nitrogen of the soil (in humus), or that applied in the form of 
cotton-seed meal, dried fish, &c., which are also largely soluble when applied, is 
rapidly converted by the process of ‘“Nnirrrricarton” under favourable 
conditions into nitrates, which are readily available to plants, but which pass 
out in the drainage, and are lost if not promptly taken up by the plant. 
Experiments have been reported in which the loss of nitrogen in the 
drainage from a bare soil in the course of a year was over 160 lb. per acre, 
while the loss from a soil which was kept covered by a crop was almost 
insignificant, although fully as large amounts of nitrates were formed in the 
latter case as in the former. This affords a striking illustration of the ~ 
importance of keeping a neacny soil covered with a crop in order to prevent 
serious loss of the most expensive element of fertility—nitrogen. Such a 
practice would protect the soil from both Leacuine and surface washing— 
probably the two most serious causes of decline of fertility of soils. 
The terms “NITRIFICATION ” and “ LEACHING ” require now to be explained. 
The word nirriFricarion simply means providing the nitrogen required by plants 
in a form immediately available as plant food. Thus, sulphate of ammonia and 
nitrate of soda are rich in nitrogen, and they contain it in a soluble form, so 
that it can be readily taken up by the plant. In some combinations the nitrogen 
is not so readily available, and a process of oxtpaTron is necessary to cause 
the materials containing the nitrogen to decompose and so release the nitrogen 
and make it available for the plant’s use. 
Our air is made up, as you know, of nitrogen and oxygen, and the nitrogen 
in the air is a free gas. Some of this free nitrogen is changed into AMMONIA 
GAs in the air, and is brought down to the earth in the rain. But plants cannot 
make use of this free nitrogen through their leaves or roots, although some 
plants, notably those of the pea family (legumes) do manage to get more 
nitrogen than can be accounted for on analysing the soil. They are found, as 
you will remember, to have little nodules attached to their roots. These nodules 
contain a tiny microscopic plant which is able to seize upon the nitrogen of the 
air which has passed into the soil with the rain, and so act upon it that it 
changes into a form which the plant ean take up as food, thus nrrrivyine the soil. 
Let me give you an example of nitrification. Away in the far West of 
Queensland, a gardener was employed on a station to raise fruit and vegetables. 
This gardener happened to be a man of great observation, with a large experi- 
ence of his profession. On one occasion he had the idea that the old garden 
was getting “played out” for certain crops, so he chose a new site, and soon 
discovered that one deficient element in the soil was nitrogen. How to supply 
this necessary ingredient was the puzzle. He was 180 miles from a railway 
station and 350 miles from any large town where it could be obtained in any 
form. Suddenly it struck him that on a portion of the old garden beans had 
been grown frequently in succession. You will remember that I told you that 
beans, peas, and some other legumes collect nitrogen from the air and supply it 
to the soil. So he carted a quantity of the soil from this part of the old garden 
and dressed a crop of Chinaman’s beans with it, leaving, however, one row 
undressed. When the crop was gathered he found that the dressed portion 
yielded 25 per cent. more than the undressed, and, moreover, the beans 
flowered and came to maturity four weeks sooner. Thus he had nitrified the 
soil. LeacninG is the washing out of plant food from the soil by heavy rain 
- or by drainage. 
So much for theory ~now for practice. I will suppose that your farm 
requires draining in some parts owing to the retention of stagnant water. This 
stagnant water has to be got rid of before the low-lying land will yield good 
crops. Let us take the simplest form of drain first. : 
