the role of compost in soil
TRANSCRIPT
Introducing by
2006-2007
Introduction
Composting organic wastes is
an environmentally sound
means
of recycling raw organic
materials into valuable soil
amendments with many
uses .
Why use compost?
• Composting is a method of stabilizing organic wastes by the action of microorganism
• Increasing soil organic matter 30t/ha compost provides ~ 6 t/ha of organic matter = long-term benefits for soil structure, fertility and water holding
• Slow release nutrients 30 t/ha compost is worth ~ £90/ha
• Increasing soil microbial population
• Stabilizing soil pH (fertilizers acidify soil) Better crop establishment & yields
The composting process
The basic process is very simple:•Collection of suitably balanced feedstock
materials
•Shredding
•Composting
•Maturation
•Screening
•Application of finished product
Distributed by: Information Packaging Centre Alberta Agriculture, Food and Rural Development 7000 - 113 Street, Edmonton, Alberta Canada T6H 5T6
Material flow for the conventional composting process.
How does composting work?
Types of composting
-Farmyard manure (FYM)
-Poultry Manure
-Cattle slurry
-Town refuse
-Sewage sludge
Characteristics of compostGeneral properties of green waste compost
pH8.6
Electrical conductivity (dS cm-1)0.773
Dry matter(%) 59
Density (kg L-1)0.5
Organic matter(%) 19
Characteristics of compost
Nutrient contents
Contamination with heavy metals (mg/kg dry weight)
Contamination with heavy metals (mg/kg dry weight)
Contamination with heavy metals (mg/kg dry weight)
HM loading rates(kg metal/ha/year when compost applied at
35t/ha/yr)
Contamination with inert fragments(% by weight)
The effects of compostapplication
Greater diversity ofsoil organisms
Improved soil structureand water retention
Supply of plantnutrients
Suppression of plantpathogens
Effects on soil chemistry
• The nitrogen in compost is very stable and is only released slowly – there is therefore little risk of it being leached
• Compost is a good source of potassium (in a readily available form)
• Compost is a reasonably good source of phosphorous
• Trace elements are also retuned to the soil
Copper addition when organic materials are spread (g/ha/yr)
Zinc addition when organic materials are spread (g/ha/yr)
Organic matter additions (250 kg/ha N)
Effect of organic matter inputs on topsoil available water capacity (AWC)
Compost can help conserve soil moisture
Moisture at 10 cm
Effect of organic matter inputs on topsoil microbial biomass-
An example of the effects on crop yields
Yie
ld (
per
cen
t o
f co
ntr
ol)
Potatoes Onions Cabbages Carrots
Effect of organic matter inputs on topsoil microbial biomass
Effect of total nitrogen inputs on topsoil PMN (potentially mineralisableN)
Effects on soil structure
• Organic matter additions improve soil structure on both heavy and light land.
• This has beneficial effects on water holding capacity, drainage, erosion and root penetration.
• Cultivations are made easier.
Effects on soil biology
• Biological activity is stimulated by the addition of nutrients and by the improvement to soil structure
• Some evidence suggests that there can be inhibition of plant diseases
Maximum supply of soil microelements and heavy metals content
ElementUnited Land (mg/kg) United Kingdom (Kg/h)
Zn1000560
Cu400280
Ni10070
Cd1050
Pb2501000
Hg22
Cr-1000
Maximum limit for soil microelements and heavy metals content due to supply compost
(mg/kg soil)
ElementLand
UnitedEngland
European United
Germany
Zn150300300300
Cu50135140100
Ni50757550
Cd2333
Pb100300300100
Hg144.52
Cr150--100
ConclusionsComposting can be an effective way of
managing organic wastes.
On-farm composting is a useful technique for dealing with farm generated wastes – bringing in material from elsewhere can be a good business in itself.
Application of compost adds to the organic matter in the soil
Compost is a good source of available P and K.
The nitrogen it contains is in a stable state and relatively unavailable in the short term.