794 
Supplement to the " Tropical Agriculturist." [May 2, 1904, 
The greater the amount of humus, mould or 
■vegetable matter the greater the number of 
bacteria and growth. As we pass below the sur- 
face the number rapidly diminislies. In 3 feet or 
4 feet the numbers are few, and at 6 feet they 
have disappeared altogether. To the activity of 
these organisms in soil we are indebted for the 
continuous releasing of plant-food, and without 
■which we now know that this earth's surface 
would be absolutely uninhabitable. We have now 
transferred the application of bacteriology from 
the academic arena of science to every dny life on 
the farm. It is known that the soil, animals and 
crops contain certain essential elements such as 
nitrogen, potash, phosphorous, magnesium, 
sulphur, sodium, iron, chlorine, silicon, and 
lime. Those subject to most rapid exhaustion in 
the soil are nitrogen, phosphoric acid and potash. 
They must be in proper proportions suitable for 
plant-food. Soils may contain them in full 
quantity, but may be sterile through absence of 
water or warmth. The physical nature of the soil 
is also a factor. Practical fertility, it will be 
noted, depends on many conditions. X»ne acre of 
maize of fifty bushels removes approximately 
96'2 lb. nitrogen, 32 lb. phosphoric acid, 56 lb. 
potash. One acre of wheat of thirty bushels 
removes about lb. nitrogen, 9| lb. phosphoric 
acid, 13| lb. potash. Kitrogen is the most 
expensive constituent of all fertilisers. We know 
that every crop removed from the land, such as 
grain, milk, roots and flesh, takes with it certain 
plant-food in varying proportions, and whilst the 
soil contains vast stores of plant-food, our 
business is to release it. An axiom every farmer 
should have in mind is : "That all sources' of 
manures or fertility from the farm and its 
surroundings should be fully utilised before 
resort is had to purchashed plant-food." A manure 
is a substance necessary to the growth of a crop, 
and not contained in the soil insufficient quantity 
or in proper form for immediate consumption. 
There are bulk manures and soil dressings avail- 
able in New South Wales to the farmer from which 
he can secure in an economic way fertilisers — such 
as farmyard and animal manures, also bird manures 
of all kinds. Refuse from wool-sheds, abattoirs, 
digesters, blood, hair, horn, &c. ; refuse from 
boiling-down works, cattle-yards, glue, starcli, 
iam factories, canning works, rabbit-preserving 
works, tanneries, gas-work retorts, brick and tile 
yards, market shops, the refuse from fires, turf 
skimmings (the most abundant and valuable 
dressings) ; deposits of soil and humus on flats, 
in gorges, dry beds of creeks, streams, lagoons, 
rivers, dredgings from rivers, lake?, and billa- 
bongs; nightsoil, road scrapings, street sweepings, 
drainage from sewers and cess-pits, malt dust, 
rotted hay and straw, maize stalks, swamp grass, 
leaves and bush-rakings (when fermented and 
decomposed) ; peat and rich fibrous soil from old 
bog lands ; guano existing in caves inland (bats) 
or by the sea shore on islands; fish refuse, coal- 
dust coal-ashes, sea-weed, sea-shells and shell 
drift (which occurs even inland) ; lime, marl, 
cypsum, ashes, and sand. Green manures — 
peas, beans, cowpeas, vetchee.'lupins, soy-beans, 
velvet beans, tangier peas, clover, lucerne, rye, 
barley, rape, mustard, dandelion, weeds, &c. 
One of the main features of manuring is to return 
humus to the soil either in the form of stubbles, 
the roots of crop?, green manures, the dung of 
grazing animals or farm-yard manures. Humus 
increases the water-holding and retaining capa- 
city of the land. It improves its physical and 
mechanical condition, renders the soil more easily 
ajrated, adds bacteria to the soil, and provides 
food for their growth and propagation. Deep 
and thorough cultivation means enhanced profits, 
and is the first consideration of every skilled 
farmer, combined with suitable drainage. The 
stores of plant-food lying latent and sterile at a 
depth need the reviving influences of sunlight, 
air, moisture and bacteria. These ageticies release 
and render soluble and available the chemical 
constituents essential to the growth of plant life. 
The first consideration is the fixing of nitrogen 
from the atmosphere in which soil bacteria render 
great service. This is effected in a metabolic 
sense by the products of bacteria nitrifying 
the soil or chemicallj' changing the insoluble 
nitrites to soluble nitrates. Pood that has lain 
for centuries is thus brought into requisition. 
Bacteria require food, which they obtain from 
organic matter, and which they decompose or 
cause to decay ; they need oxygen from the air, 
and further need moisture to stimulate their 
growth and function?. Green manure is produced 
by any crop that is grown primarily for the 
purpose of improving the soil and not for its 
harvested product. It is found in sound farming 
practice to grow these between ordinary crops 
to either plough them in or feed them off with 
any of the domestic animals, preferably sheep. 
(1 ) The chief aim of green manuring or by turning 
in green crops is to increase the supply of humus, 
organic matter or mould in the soil. The term is 
applied to some quickly-growing crop which is 
ploughed in green ; and that is best conducted when 
the crop is young and during warm weather, so that 
it may decay, rot, or decompose rapidly. (2) 
Not only does this form of manure add humus 
to the soil, but improves its physical condition or 
texture. The soil is made more friable and looser, 
and more easily serated. Moreover, in our warm 
climate it increases the moisture-holding capacity 
of the soil and makes it mors retentive. Two 
classes of plants are used for the purpose of green 
manuring : (l)Rape, rye, buckwheat, cape barley, 
dandelion, mustard, and weeds. (2) The legu- 
minous crops — peas, beaus, soy-beans, lupins, 
cow-peas, clovers, vetches, pea-nuts, lucerne, 
&c. With the leguminous crops is secured the 
dual advantage of not only adding humus to the 
soil, but also transraittiiig stores of nitrogen from 
the atmosphere to the soil, but indirectly releasing 
plant-food and by rendering it available. Cow- 
peas, soy-beans, tangier pea, can be grown in 
summer ; clovers, peas, vetches or tares, &c., 
in winter. Crimson clover and black vetches are 
both valuable fodder plants in this district*. Ex- 
periments showed that a crop of clover 18 inches 
* Hawkesbury District. 
