What is Humus? Humus is plant and animal remains which is slowly rotted in the soil. The agents of decay are the enormous amount of bacteria and other microscopic organisms which thrive every ounce of earth. They break down dead roots and underground insects as well as the fallen leaves carried below the surface by worms. Partially decomposed organic matter with the horde of living and dead bacteria is called Humus.

Soil without humus is nothing more than finely ground rock. Humus is important as it contains and maintains the vast populace of microscopic organisms in the soil. These bacteria are the key to fertility, and they have a beneficial effect both before and after death.

When they are alive they create heat and transform complex organic substance into forms that will later become available to the roots. When they are dead they let loose these plant foods coupled with colloidal gums. To the soil scientist it is these gums and not plant remains which are humus - the magical material which cements the soil crumbs together.

Under natural circumstances there is a rough and ready balance which maintains the humus level of your soil. Under cultivation, however, the humus content declines and so within the garden it is essential to consistently replenish the source. Last year's dead plants and dead worms simply aren’t enough, you have to add humus-makers. Many varieties are available, and they all fall into one or other of three basic types.

Raw Humus -Makers:

These organic materials contain enough readily-available nutrients to stimulate active bacterial growth. Heat is created and soil structure is enhanced, hot beds made with fresh manure were producing early vegetables before electricity was discovered.

Common examples are grass clippings, fresh dung, dug-in weeds and seaweed. Using raw humus-makers is an excellent way of warming the earth and building up the humus content...provided you know the limits. The sudden increase within the bacterial population robs nitrogen from your soil. So always add some nitrogen when using a raw humus-maker.

As a general rule, humus-makers of this type are used some time before planting or in an area a long way away from plant roots. The generation of warmth and the nitrogen-robbing effect can be harmful to nearby roots.

Matured Humus-Makers:

These organic materials do not contain sufficient readily-available nutrients to stimulate active bacterial growth. A raw humus-maker is transformed into a matured humus-maker by composting - a process which produces humus.

Common examples are well-rotted animal manure, properly made garden compost and Bio Humus. The warming effect on the soil is lost, but this is outweighed by the advantages. Matured humus-makers cannot damage tender roots and the nitrogen content of your soil remains available rather than being partly locked up in bacterial bodies.

All matured compost-makers contain the colloidal gums released by dead bacteria during the composting process. Unlike the fibrous humus-makers, they do more than enhance aeration and water-holding capacity by physical means, they also immediately provide the agents to create soil crumbs and so enhance the friability.

Fibrous Humus-Makers:

These organic materials are abundant with cellulose, but the lack of sugars and simple starches means that very little bacterial activity is stimulated. Soil improvement by these humus-makers is essentially a physical effect, bark opens up the soil and peat improves aeration and water-holding capacity.

Common examples are peat, pulverised bark and sawdust. Peat is the most inactive material, it is clean and simple to handle but it is hardly a humus-maker in the true sense of the word. It resists breakdown and so crumb-forming gums are usually not produced.

Sawdust and some bark products are slowly broken down by bacteria. This bacterial activity requires nitrogen, and the soil's supply will be robbed if you don't add a nitrogen-rich fertilizer.

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Author's Bio: 

I enjoy writing about my work, specifically the DIY projects I carry out around my home.