Abstract
AbstractAssessment of compost maturity is important for successful use of composts in agricultural and horticultural production. We assessed the "maturity" of four different sawdust-based composts. We composted sawdust with either cannery waste (CW), duck manure (DM), dairy (heifer) manure (HM) or potato culls (PC) for approximately one year. Windrows were turned weekly for the first 60 days of composting, covered for four winter months and then turned monthly for six more months. We measured compost microbial respiration (CO2 loss), total C and N, C:N ratio, water soluble NO3-N and NH4-N, dissolved organic carbon (DOC), pH and electrical conductivity at selected dates over 370 days. Compost effects on ryegrass biomass and N uptake were evaluated in a greenhouse study. We related compost variables to ryegrass growth and N uptake using regression analysis. All composts maintained high respiration rates during the first 60 days of composting. Ammonium-N concentrations declined within the first 60 days of composting, while NO3-N concentrations did not increase until 200+ days. After 250+ days, DM and PC composts produced significantly more ryegrass biomass than either CW or HM composts. Total C, microbial respiration and water-extractable NO3-N were good predictors of compost stability/maturity, or compost resistance to change, while dissolved organic carbon, C:N ratio and EC were not. The compost NO3-N/CO2-C ratio was calculated as a parameter reflecting the increase in net N mineralization and the decrease in respiration rate. At ratio values >8 mg NO3-N/mg CO2-C/day, ryegrass growth and N uptake were at their maximum for three of the four composts, suggesting the ratio has potential as a useful index of compost maturity.
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Claims 9
Claim · model-written summary
All composts maintained high respiration during the first 60 days.
Not reportedTaxon
Verbatim
e0“All composts maintained high respiration rates during the first 60 days of composting.”
Claim · model-written summary
Compost ammonium-N declined within 60 days.
- Outcome
- Ammonium-N concentrationse0
- Direction
- declinede0
- Qualifier
- within the first 60 days of compostinge0
Not reportedTaxon
Verbatim
e0“Ammonium-N concentrations declined within the first 60 days of composting, while NO3-N concentrations did not increase until 200+ days.”
Claim · model-written summary
Compost nitrate-N did not increase until after 200 days.
Not reportedTaxon
Verbatim
e0“Ammonium-N concentrations declined within the first 60 days of composting, while NO3-N concentrations did not increase until 200+ days.”
Claim · model-written summary
After 250 days, DM compost produced significantly more ryegrass biomass than CW or HM composts.
- Treatment
- DMe0
- Outcome
- ryegrass biomasse0
- Direction
- moree0
- Qualifier
- After 250+ dayse0
- Comparator
- CW or HM compostse0
LoliumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 250+ days, DM and PC composts produced significantly more ryegrass biomass than either CW or HM composts.”
Claim · model-written summary
After 250 days, PC compost produced significantly more ryegrass biomass than CW or HM composts.
- Treatment
- PC compostse0
- Outcome
- ryegrass biomasse0
- Direction
- moree0
- Qualifier
- After 250+ dayse0
- Comparator
- CW or HM compostse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 250+ days, DM and PC composts produced significantly more ryegrass biomass than either CW or HM composts.”
Claim · model-written summary
Total carbon, microbial respiration and extractable nitrate were good predictors of compost stability or maturity.
- Outcome
- compost stability/maturitye0
- Direction
- good predictorse0
- Qualifier
- Total C, microbial respiration and water-extractable NO3-Ne0
Not reportedTaxonComparator
Verbatim
e0“Total C, microbial respiration and water-extractable NO3-N were good predictors of compost stability/maturity, or compost resistance to change, while dissolved organic carbon, C:N ratio and EC were not.”
Claim · model-written summary
DOC, C:N ratio and EC were not good predictors of compost stability or maturity.
Not reportedTaxonComparatorDirection
Verbatim
e0“Total C, microbial respiration and water-extractable NO3-N were good predictors of compost stability/maturity, or compost resistance to change, while dissolved organic carbon, C:N ratio and EC were not.”
Claim · model-written summary
Ryegrass growth and N uptake were maximal above a nitrate-N to respiration-carbon ratio of 8 for three composts.
- Treatment
- compostse0
- Outcome
- growth and N uptakee0
- Direction
- maximume0
- Value
- >8 mg NO3-N/mg CO2-C/daye0
- Qualifier
- three of the four compostse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At ratio values >8 mg NO3-N/mg CO2-C/day, ryegrass growth and N uptake were at their maximum for three of the four composts, suggesting the ratio has potential as a useful index of compost maturity.”
Claim · model-written summary
The ratio has potential as a compost maturity index.
Not reportedTaxon
Verbatim
e0“At ratio values >8 mg NO3-N/mg CO2-C/day, ryegrass growth and N uptake were at their maximum for three of the four composts, suggesting the ratio has potential as a useful index of compost maturity.”
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