This material is part of my lecturing on soi fertility, fertilizer, and fertilization namely Chapter 6 The OM and SOM written down based on the book of Benjamin Wolf and George H. Snyder. 2002. This material is only for lecture purpose of my class.

1. Chapter 6. THE ORGANIC MATTER AND THE SOIL ORGANIC MATTER
The place of O.M. to sustain soil productivity
6.1. Introduction: how to understanding?, definition
6.2. The role of SOM in soil productivity
6.3. The classification of SOM
6.4. Organic fertilizer
(For Agro-technology Study Program – FAPERTA UNSOED)
Purwandaru Widyasunu Soil Sciences Laboratory, Faperta, Unsoed. 2011. Copy in PDF by 2014.

2. 6.1. Introduction, definition
The place of organic matter in providing sustainable soil, what is mean???
Sustainable agriculture is not possible without sustainable soil. But soil cannot be sustained without satisfactory SOM, which in turn is largely dependent on OM additions and how they are handled.
The dependent of sustainable agriculture on organic matter originates from the many beneficial effect of both OM and SOM forms.
SOM consist of wide variety of plant and animal tissues in various stages of decomposition. Various stage: fresh (non-decayed), slightly decayed, the decayed, and finally forms THE HUMUS.

3. HUMUS is more stable than the organic materials from which it is derived. Humus is transitory in nature and will break down, albeit very slowly, the rapidity increasing in soils with ample oxygen and good moisture levels and at elevated temperatures. Both OM and SOM are largely responsible for soil formation and development. What is implication of the soil development on soil productivity???

4. 6.2. The role of SOM in soil productivity What processes can (we) hope with SOM???
 Soil formation and development
 The energy derived from the decay supports the living microorganisms(bacteria, fungi, actinomycetes). These organisms are constantly modifying the rocks from which soil is formed, releasing nutrient for plants.
 The more benefit of energy: benefit to larger organisms (mites, earthworm, and insects) that intimately mix the fine rock fragments with OM, greatly hastening the decomposition of the rock and speeding soil formation.
Maintaining large number of diverse of organisms, the OM helps maintain balance a healthy balance between beneficial and disease organisms.

5. The more benefits be hope By SOM and added OM in soil:
The SOM and new OM supplies energy use for many useful processes, without which it would become difficult IF NOT impossible to provide satisfactory production.
Some important processes for agriculture supported by the energy derived form OM:
1.The decomposition release slowly of nutrient for plant.
2.The SOM provide living N2 fixation microorganism from N unavailable to N available to plant.
3.The sustenance of mychorrhiza fungi that help keep P in an available form.
4.The support of bacteria, actinomycetes, and some filamentous fungi that aid in the formation of cements so essential for binding individual small soil particles into aggregates or peds.

6. THE SOM and added OM improves soil physic: The aggregates formed greatly improved soil structure and lessen soil bulk density. The improved soil structure markedly improved crop production by:
1.Improving water infiltration, thereby lessening soil erosion and increasing the amount of available water.
2.Increasing air porosity, which allows better movement of air and water in soils.
3.Providing an ideal environment for beneficial microorganisms and plants roots.
4.Aiding good tilth, which is necessary for ease in soil preparation as well as rapid development of seedlings and plants.
5.Reducing erosion by aiding infiltration, and favoring certain soil characteristic that aid in the movement of suitable amounts of air and water, WITHOUT which crop production is not possible.

7. THE OM aids soil productivity in several ways:
1.Increases cation exchange capacity (CEC), allowing better retention of ammonium-N, K, Ca, and Mg.
2.Provides for chelation of several micro nutrients, which helps keep them available.
3.Helps keep P available, particularly at both high and low pH values.
4.Buffers soil, limiting rapid changes in pH or salt content that can occur with addition of various chemicals.
5.Decreases dispersion of soil by rain drops or irrigation and thus lessen surface crust and compaction.
6.Lessen changes in soil temperatures, which could interface with nutrient availability and plant survival.

8. THE EFFECT OF OM AND SOM thought to:
1.Soil physic
2.Soil chemistry
3.Soil biology Through:
1.The energy supply produces
2.The carbon and other binding agent supplies by OM decomposition
3.The carbon, hormone, nutrient affect soil biota.

9. 6.3. The classification of SOM Classification based on OM: size, age, maturity, source Size: (i) very fine, (ii) fine, (iii) medium, (iv) coarse. Age: (i) fibric (young), (ii) hemic (medium), (iii) sapric (old containing humic acid). Maturity: (i) immature, (ii) slightly mature, (iii)mature. Can be defined by C/N; C/P; C/S Source: from vegetation or animal; man made or natural.

10. Basic Concept of Organic Matter OM in soils can exist as:
1.Recently added materials called organic matter (OM).
2.Decomposed materials beyond recognition, called soil organic matter (SOM). Factor affecting OM decomposition:
1.Factor of OM it self: (i) type of material (rich protein, cellulose, lignin, etc.), (ii) age (young, old), (iii)particle size, (iv) N-content or C/N.
2.Factor out side OM: (i) soil moisture, pH, aeration, temperature, nutrient content, (ii) weather: sub tropics, tropics, (iii) intensive agriculture, soil/land/environment degradation.

19. 6.4. Organic fertilizer
What is organic fertilizer:
Fertilizer is making from organic matter made by human.
Source: plant, animal(fresh or waste).
Process composting aerobic or anaerobic.
The formation of humus-like material outside the soil.
If composting in soil (by dug the soil) the materials of animal waste (faeces and urine) will become night-soil.

20. Test
Range of analysis
C/N
6:1 – 20:1
pH
5-8
Conductivity
0.2 – 2 S/m
Total N
0.5-3.0 %
P
0.1-2.0 %
K
Ca
Mg
S
0.2-1.0 %
0.8-3.5 %
0.3-0.6 %
0.1-2.0 %
Variability of several important composition criteria of compost (Wolf and Snyder 2002).

21. The mixing materials: Need some care for mixing materials in composting to have desirable product. Need a balance of wide C/N ratio materials: straw, stalks, brown leaves, wood chips, those to be mixed with narrow C/N materials such as manure animal residues, green leaves, legume hay, biosolids. Make compost to C/N < 20; if < 12 or less that means mature compost (ready to be used except of pathogenic and heavy metals content are forbidden). Use effective microorganism: LAB (lactic acid bacteria) and IMO (indigenous microorganism).

22. The compost amount desire to increase soil productivity.
 Very good soil productivity can be maintained if sufficient OM is added each year to maintain adequate porosity, allow sufficient water storage and movement, limit erosion, increase nutrients.
Guatemala soils case: 1 % org-C loss as CO2 equal to 20,000 lb dry matter/acre. That means 65 % loss of org-C during decomposition process, leaving only 35 % as SOM. Thus it needs 57,000 lb of OM to be added per acre to replace the loss 1.0 percent. Source: Benjamin Wolf and George H. Snyder. 2002. Sustainable Soils: The Place of Organic Matter in Sustaining Soils and Their Productivity. The Haworth Press, Inc.