1 Noy., 1901.] QUEENSLAND AGRICULTURAL JOURNAL. 457 
what is drawn from the air. Now, of all the substances required by crops to 
favour their growth, potash, phosphoric acid, nitrogen, and lime are those which 
are the first to disappear by removing crops; but a very serious loss takes 
place in drainage water. Some plant foods, such as the cutorrpEs and NITRATES 
of soda and lime are very easily washed away; whereas potash, ammonia, and 
phosphates are kept from washing away by the rErENTIVE power of the clayey 
portions of the soil. You see, therefore, what a loss of plant food must occur 
during heavy, long-continued rains. During the great flood of 1893 the 
shallower soils on the banks of the Brisbane and other rivers were so washed. 
out that on some previously fertile farms no crop would afterwards grow. 
The amount of nitrogen carried away from an acre by heavy rains has been 
ascertained to be about 40 Ib., which is equal to the whole of the nitrogen 
required for a crop of wheat or barley. 
Well, when the very soluble plant food mentioned has all gone from the 
surface soil, the land requires to be renovated and once more brought to a state 
of fertility, and the most natural thing to occur to you would be to supply that 
which is deficient in it. 
GREEN MANURING is the simplest way of supplying organic matter or 
HuMUS. For this purpose cow peas, velvet beans, vetches, or any quick- 
erowing crop are sown, and when they attain a convenient height they are 
ploughed. under. 
In hot climates such as ours this is a very simple way of improving a soil 
wanting in organic matter. The green plants rot very quickly and form humus, 
restoring to the soil not only all they took out of it, but also nitrogen and carbon 
they collected from the air. Plants grown for this purpose should be ploughed 
in before the seed ripens. Remember, the best plants for this purpose are 
LEGUMINOUS crops such as those mentioned, and you may include rape, vetches, 
lupins, and clover. 
Now, what does this green manuring do for the land? First, it opens up 
and loosens the soil, then it supplies the nitrogen it has collected for the use 
of the coming crop, and then also certain salts in a fit state for plants to 
take up. 
We will now consider Farmyard Manure, which, as has already been 
explained (10th Lesson, First Stage), is the best general manure, the only objec- 
tion to it being that a large quantity of material is carted on to the field which 
is of little or no value to a crop. 
Of inorganic substances it contains soda, lime, magnesia, potash, oxide 
of iron, silica, chloride, phosphoric acid, and carbonic acid. 
Of organic substances it contains the various compounds of nitrogen 
forming ammonia and humic acids, which form the main portion of humus 
whence plants derive their nitrogen. Thus farmyard manure is a perfect 
manure, and affords the best means of preserving the fertility of the soil, for 
not only does it furnish a supply of plant food immediately available, but it 
leaves a supply in the soil which only gradually becomes available for a subse- 
quent crop. 
When farmyard manure is thoroughly well fermented or rotted, it is called 
“short” manure; when unfermented, the straw has scarcely undergone any 
change, and the name of “long manure” is given to it. Short manure is best 
applied to light porous soils, because its. ingredients are more quickly taken up 
by the plants, and loss by drainage is to a great extent avoided, whilst clayey 
and stiff soils generally benefit more by long manure, whose ingredients are 
held by the stiff soil until they have undergone the changes which fit them 
for nourishing the plants. The long straw also helps to AzratE—that is, to 
admit the passage of air through the clay soil, and so helps to sweeeten and 
loosen it. 
Great care is needed to prevent any loss of the liquid matter of the 
manure-heap, and also to prevent loss of votartie elements, such as ammonia, 
by evaporation (volatile is applied to such substances as “fly away” in the 
form of gas). 
