Abstract
Nutrient-rich organic wastes and soil ameliorants can benefit crop performance and soil health but can also prevent crop nutrient sufficiency or increase greenhouse gas emissions. We hypothesised that nitrogen (N)-rich agricultural waste (poultry litter) amended with sorbents (bentonite clay or biochar) or compost (high C/N ratio) attenuates the concentration of inorganic nitrogen (N) in soil and reduces emissions of nitrous oxide (N2O). We tested this hypothesis with a field experiment conducted on a commercial sugarcane farm, using in vitro incubations. Treatments received 160 kg N ha−1, either from mineral fertiliser or poultry litter, with additional N (2–60 kg N ha−1) supplied by the sorbents and compost. Crop yield was similar in all N treatments, indicating N sufficiency, with the poultry litter + biochar treatment statistically matching the yield of the no-N control. Confirming our hypothesis, mineral N fertiliser resulted in the highest concentrations of soil inorganic N, followed by poultry litter and the amended poultry formulations. Reflecting the soil inorganic N concentrations, the average N2O emission factors ranked as per the following: mineral fertiliser 8.02% > poultry litter 6.77% > poultry litter + compost 6.75% > poultry litter + bentonite 5.5% > poultry litter + biochar 3.4%. All emission factors exceeded the IPCC Tier 1 default for managed soils (1%) and the Australian Government default for sugarcane soil (1.25%). Our findings reinforce concerns that current default emissions factors underestimate N2O emissions. The laboratory incubations broadly matched the field N2O emissions, indicating that in vitro testing is a cost-effective first step to guide the blending of organic wastes in a way that ensures N sufficiency for crops but minimises N losses. We conclude that suitable sorbent-waste formulations that attenuate N release will advance N efficiency and the circular nutrient economy.
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Claims 11
Claim · model-written summary
Crop yield was similar across nitrogen treatments.
Verbatim
e0“Crop yield was similar in all N treatments”
t0“Sugarcane”
Claim · model-written summary
Poultry litter plus biochar yield statistically matched the no-nitrogen control.
Verbatim
e0“the poultry litter + biochar treatment statistically matching the yield of the no-N control”
t0“Sugarcane”
Claim · model-written summary
Mineral nitrogen fertilizer produced the highest soil inorganic nitrogen concentration.
Verbatim
e0“mineral N fertiliser resulted in the highest concentrations of soil inorganic N, followed by poultry litter and the amended poultry formulations”
t0“Sugarcane”
Claim · model-written summary
Mineral fertilizer had an 8.02% N2O emission factor.
Verbatim
e0“Reflecting the soil inorganic N concentrations, the average N2O emission factors ranked as per the following: mineral fertiliser 8.02% > poultry litter 6.77% > poultry litter + compost 6.75% > poultry litter + bentonite 5.5% > poultry litter + biochar 3.4%”
t0“Sugarcane”
Claim · model-written summary
Poultry litter had a 6.77% N2O emission factor.
Verbatim
e0“Reflecting the soil inorganic N concentrations, the average N2O emission factors ranked as per the following: mineral fertiliser 8.02% > poultry litter 6.77% > poultry litter + compost 6.75% > poultry litter + bentonite 5.5% > poultry litter + biochar 3.4%”
t0“Sugarcane”
Claim · model-written summary
Poultry litter plus compost had a 6.75% N2O emission factor.
Verbatim
e0“Reflecting the soil inorganic N concentrations, the average N2O emission factors ranked as per the following: mineral fertiliser 8.02% > poultry litter 6.77% > poultry litter + compost 6.75% > poultry litter + bentonite 5.5% > poultry litter + biochar 3.4%”
t0“Sugarcane”
Claim · model-written summary
Poultry litter plus bentonite had a 5.5% N2O emission factor.
Verbatim
e0“Reflecting the soil inorganic N concentrations, the average N2O emission factors ranked as per the following: mineral fertiliser 8.02% > poultry litter 6.77% > poultry litter + compost 6.75% > poultry litter + bentonite 5.5% > poultry litter + biochar 3.4%”
t0“Sugarcane”
Claim · model-written summary
Poultry litter plus biochar had a 3.4% N2O emission factor.
Verbatim
e0“Reflecting the soil inorganic N concentrations, the average N2O emission factors ranked as per the following: mineral fertiliser 8.02% > poultry litter 6.77% > poultry litter + compost 6.75% > poultry litter + bentonite 5.5% > poultry litter + biochar 3.4%”
t0“Sugarcane”
Claim · model-written summary
All measured emission factors exceeded both default factors.
Verbatim
e0“All emission factors exceeded the IPCC Tier 1 default for managed soils (1%) and the Australian Government default for sugarcane soil (1.25%)”
Claim · model-written summary
Laboratory incubations broadly matched field N2O emissions.
Verbatim
e0“The laboratory incubations broadly matched the field N2O emissions”
t0“Sugarcane”
Claim · model-written summary
The authors recommend sorbent-waste formulations that attenuate nitrogen release to advance nitrogen efficiency.
Verbatim
e0“suitable sorbent-waste formulations that attenuate N release will advance N efficiency and the circular nutrient economy”
t0“Sugarcane”
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