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Temperature
-More rapidly in the tropics than in temperate areas.
-continuous warmth in the tropics implies that high equilibrium levels of organic matter are difficult to achieve in tropical agro-ecosystems.
-Hence high rates of organic matter inputs are needed to maintain labile soil organic matter.
-Soils in cooler climates commonly have more organic matter because of slower mineralization (decomposition) rates.
Soil moisture and water saturation
Soil saturated with water lead to poor aeration due to reduction of oxygen in the soil leads to a reduction of the mineralization rate as these organisms become inactive or even die.elevated levels of soil moisture result in greater biomass production, which provides more residues, and thus more potential food for soil biota. Optimal microbial activity occurs at near “field capacity”, which is equivalent to 60-percent water-filled pore space.
Soil texture.
Soil organic matter tends to increase as the clay content increases.
This increase depends on two mechanisms. First, bonds between the surface of clay particles and organic matter retard the decomposition process. Second, soils with higher clay content increase the potential for aggregate formation.the organic matter content in fine textured (clayey) soils is two to four times that of coarse textured (sandy) soils.
Salinity and acidity.
-Salinity, toxicity and extremes in soil pH (acid or alkaline) result in poor biomass production and, reduced additions of organic matter to the soil.
-pH affects humus formation in two ways: decomposition, and biomass production.
Vegetation and biomass production:
applications of readily degradable materials with low C:N ratios, such as green manure and leguminous cover crops, favour decomposition and a short-term increase in the labile nitrogen pool during the growing season.
On the other hand, applications of plant materials with both large C:N ratios and lignin contents such as cereal straw and grasses generally favour nutrient immobilization, organic matter accumulation and humus formation, with increased potential for improved soil structure development.
jim items answered the question on April 6, 2018 at 09:07
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