core soil properties #3 soil organic matter Flashcards
what does soil organic matter consist of
it consists of plant and animal detritus at various stages of decomposition, cells and tissues of soil microbes, and substances that soil microbes synthesize
how much carbon is contained in SOM compared to vegetation and atmosphere combined
almost twice as much
what does decomposition do for organic matter
transforms and destroys it
what is a way that Carbon in the soil can be lost
it can be oxidized to carbon dioxide during microbial respiration
what is soil organic matter (SOM) composed of
living organisms- the soil biomass
plant litter- deads roots, leaves, and another plant residue at various stages of decaying
dissolved organic biomolecules- range from amino acids released from plant roots to enzymes produced by microorganisms (these substances degrade quickly; they are considered to have a fast turn around rate)
stable soil organic matter (humus)- has a slow turnaround rate
what are the benefits of SOM on soil physical properties
- increases soil aggregation (improving soil structure)
- improves water filtration rate (reducing water runoff and erosion)
- improves water holding capacity, especially of sandy soils
- reduces plasticity and stickiness of clay soils (making them more workable)
- reduces surface crusting (making it easier to plant seeds next)
what are the benefits of SOM on soil chemical properties
- like clay, it can hold nutrients in an easily exchangeable form
- nutrients including N, P, and S are also stored this is important for soil fertility
- organic acid can accelerate the weathering of rocks and minerals which releases nutrients for plants
what are the benefits of SOM on soil biological properties
- provides food for the community of soil organisms
- the type and diversity of organic residue will affect the diversity of soil organisms (improved soil biodiversity can help in the suppression of diseases and pests)
- enhances pore space through the actions of soil microorganisms; this helps to increase water infiltration and reduce runoff
how do we maintain a positive balance between gains and losses of SOM in an agricultural system
maximize inputs, reduce losses
what are the benefits of fresh residue
- insulates soil
- reduces wind and where erosion
- decomposition of fresh residue releases nutrients for plants
what are the benefits of hummus
- soil water holding capacity
- soil fertility
- soil structure
- erosion resistance
what do grasslands have darker surface colours than forest soils
because grasslands tend to store more soil organic matter in the surface layer
what are ways we can maximize soil organic inputs with plant residue
return residues to the soil fertilize with sufficient nutrients for high productivity add cover crops for off-season growth grow more perennials complex crop rotation
what are ways we can maximize soil organic inputs with animal inputs
recycle manure and bedding
manure and urine from grazing
what are ways we can maximize soil organic inputs by recycling offsite biomaterials
apply compost, organic mulch, and biochar
where regulations allow, municipal sewage sludge may be applied
