HUMUS AND ANIMAL MANURES - Part 1

Articles In This Section:

· PLANT FOODS

· ANALYSIS OF PLANT ASH

· ORGANIC WASTE MATTER

· MAJOR PLANT FOOD ELEMENTS

· MINOR PLANT FOOD ELEMENTS - Part 1

· MINOR PLANT FOOD ELEMENTS - Part 2

· FOLIAGE FEEDING

· SOIL ACIDITY OR ALKALINITY

· HUMUS AND ANIMAL MANURES - Part 1

· HUMUS AND ANIMAL MANURES - Part 2

· VEGETABLE MANURES

· COMPOST

· LIQUID MANURES

Fertile soil is not merely disintegrated rock holding the necessary plant nutrients in its interstices; it is vastly more than this. The fertility of soil depends on its content of humus, its drainage, and the chemical composition of the food in it. Humus has many functions; it increases the water-holding capacity of the soil, it improves the tilth and aeration, and it darkens the soil, thereby steadying temperature variation. Without humus, soil micro-organisms cannot exist. They feed on it and in so doing break it down into soluble plant foods.

The number of micro-organisms in a soil of average fertility has been estimated to reach tens of millions to the saltspoonful. They represent one of the basic factors in soil fertility and vary greatly in type. Very little bacteriological research has yet been done, but we know that some break down organic matter and that others dissolve it and assist roots in absorbing it, a symbiotic relationship. Rootlets and certain soil fungi (my-corrhizae) exist in such intimate association that there is no clear demarcation between rootlet and fungus; this is called mycorrhizal association. It is neither an accident nor a parasitic infection.

Soil fungi and bacteria are reduced to small numbers in soils that are dry or deficient in organic matter. They are killed by poisons applied to the soil (some weed-killers, some "fertilizers", and some plant sprays) or by waterlogging, which leads to lack of oxygenation and the generation of marsh gas and sulphuretted hydrogen by putrefaction.

Animal manures, as usually stored in Australia, lose most of their nitrogen by volatilization when exposed to heat and dry-ness, and by drainage when exposed to wet. Under wet conditions nearly all of the potash will drain away from any manure as well. Thereafter the value of the manure is largely mechanical, improving sandy soils by giving them body, and heavy soils by increasing their porosity and friability. It dis-appears under the disintegrating influence of soil bacteria, slowly and regularly yielding foods. Any manure rich in nitrogen is said to be "hot" or "rich"; it should be used sparingly

Cow dung is very slowly oxidized and so its effects in soil are lasting. It is particularly useful in sandy soils and in hot, dry climates. Gathered from the paddocks, it does not contain very much nitrogen, phosphorus, or potash. When fresh it is richer, and, if mixed with urine drained from the milking bails, is very strong in all three of these elements. Unfortunately we cannot often buy cow dung saved in this manner, but nevertheless it is probably the safest and best of all manures for roses. Most of it should be obtained in the winter; otherwise great crops of weeds will be imported too, for weed seeds are not killed by the cow's digestive processes. Weeds do not seed very much in winter.

Horse dung gathered from the paddocks and in a dry condition has very little manurial value other than as humus. It is very rich in plant foods if obtained from the stall, for it then contains urine and great quantities of straw. It is so "hot" at this time that it should not be put straight on to garden beds, but should be interlayered with soil in a heap and allowed to stand for a couple of weeks.