Organic Wastes Amended with Sorbents Reduce N2O Emissions from Sugarcane Cropping

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 bioc...

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Bibliographic Details
Published in:	Environments (Basel, Switzerland) Vol. 8; no. 8; p. 78
Main Authors:	Maren Westermann, Richard Brackin, Nicole Robinson, Monica Salazar Cajas, Scott Buckley, Taleta Bailey, Matthew Redding, Jitka Kochanek, Jaye Hill, Stéphane Guillou, Joao Carlos Martins Freitas, Weijin Wang, Chris Pratt, Ryo Fujinuma, Susanne Schmidt
Format:	Journal Article
Language:	English
Published:	MDPI AG 01-08-2021
Subjects:	circular nutrient economy greenhouse gas nitrous oxide organic fertiliser poultry litter sustainable agriculture
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Summary:	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.
ISSN:	2076-3298
DOI:	10.3390/environments8080078