456 QUEENSLAND AGRICULTUEAL JOURNAL. {1 Noy., 1901. 
see how it comes about that the decay of leaves, roots, trees, &c., assists m 
rousing up the dormant ingredients in the soil. As you know, there is a great 
variety of soils, and all do not contain plant food in the same proportion. Pure 
sand, for instance, contains very little plant food ; pure clay contains elements 
which are only of value to some plants, but few, if any, will thrive on mere 
cold, sticky clay. A light sandy loam, consisting of both organic and inorganie 
matter, is one of the best soils for many crops, whilst the dark soils, rich in 
organic matter, will furnish plenty of plant food for any crop whatever. Some 
of these latter soils are so “fat” that farmers do not sow wheat on them until 
they have been cropped several times with something else. The rich organic 
matter supplies such quantities of plant food and water, even in a dry season, 
that the wheat straw grows extremely coarse at the expense of the grain. 
You now have a few more names to remember. £ course you have not 
forgotten oxygen, nitrogen, and carbonic acid gas. You must bear these names 
well in mind, because they will be constantly used in succeeding lessons. 
Questions on Lesson 8. 
What are (a) oxygen, (4) nitrogen, (¢) carbonic acid gas ? 
. Whence does carbonic acid gas get into the air ? 
Describe the action of oxygen and carbonic acid gas. 
. How is a soil formed by nature ? 
What is meant by the fertility of a soil? 
. What is organie matter? What inorganic ? 
. To which of these does humus belong ? 
. How is humus formed ? 
Do all soils contain plant food in the same proportion ? 
. Name four soils in order of their fertility ? 
SCMOMANANKRwWIe 
H 
SECOND STAGE. 
4ru Lesson. 
In Lesson 10 you saw what manurial elements go to make up the struc- 
ture of a plant, and how this was found out by Ananysts. You were also told 
that the plant derives food from organic matter contained in HUMUS and from 
the air, in the shape of Nrrroaun, OxyeEy, Carzonic Actin, &e. 
Now, in order to keep up a proper supply of all these ingredients in the 
soil, farmers whose land is becoming exhausted adopt several ways of doing so. 
I should first tell you, however, that in reality there is no such thing as an 
exhausted soil. The plant food is there, but it is out of the reach of the roots 
of the plants, and requires to be brought up in some way or another to become 
available. Constant cropping has certainly removed the fertilising matter from 
the surface, and, such being the case, good crops cannot be produced; and, in 
this sense, the land is said to be exhausted. ‘To restore the fertility of the soil, 
recourse is had to MaNuRING either with farmyard manure or with artificial 
fertilisers, or both combined, to FALLOWING, to ROTATION of crops, to GREEN 
MANURING, SUBSOILING, and DRAINING, IRRIGATION, &e. 
We will consider all these in this and the succeeding primer from a higher 
standpoint than in the first book. 
Now, let us. ask what state the soil should be brought to to be considered 
fertile. 
have already explained to you the meaning of acrivE and pDormMaym 
matter, terms used to denote souvBLE and INSOLUBLE matter. All soils, except 
peat soils, which do not exist in Queensland in the same form as in Europe, are 
formed originally from rocks, and consequently contain various minerals, such 
as lime, potash, silica, salt, iron, phosphoric acid. They also contain nitrogen, 
which is derived from the decay of organic matter in the soil, in addition to 
