Do tillage, cover crops, and compost management within organic grain cropping affect greenhouse gas emissions?

Authors: BOARDMAN, D - Howard G Buffett Foundation; CLARK, K - University Of Missouri; Kitchen, Newell; EASTERBY, S - University Of Missouri; STAPLES, J - University Of Missouri; REINBOTT, T - University Of Missouri; KREMER, ROBERT - University Of Missouri

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2018
Publication Date: 8/16/2018
Citation: Boardman, D.L., Clark, K.M., Kitchen, N.R., Easterby, S.O., Staples, J.S., Reinbott, T.M., Kremer, R.J. 2018. Do tillage, cover crops, and compost management within organic grain cropping affect greenhouse gas emissions? Agronomy Journal. 110:1893-1904. https://doi.org/10.2134/agronj2018.01.0023.
DOI: https://doi.org/10.2134/agronj2018.01.0023

Interpretive Summary: Organic grain crop production is increasing in response to consumer demand, but little research has been done on how organic management practices impact the environment. This research was conducted to evaluate how organically-grown corn, soybean, and wheat (either with or without cover crops and with and without tillage) affect carbon dioxide and nitrous oxide greenhouse gas (GHG) emissions. The research was conducted on poorly-drained claypan soils in central Missouri. Extremely dry and dry conditions persisted throughout the growing season for the first two years of this study (2012 and 2013). Since ample soil water is an essential factor for microbial activity and production of these two GHG, very low emissions occurred during these two dry years. With average precipitation amounts in 2014, carbon dioxide emissions from wheat and nitrous oxide emissions from wheat and corn increased. Emissions were not greatly affected by tillage practices or use of cover crops. Emission levels were greatest with the highest quantities of compost. Emission rates for soybean were low throughout the growing season. The GHG levels measured were generally less than that reported for conventionally-grown grain crops. This was attributed to droughty conditions and the use of compost to supply nitrogen to the crop rather than synthetic fertilizer. The results of this research will benefit the general public as they increasingly expect sustainably-grown food.

Technical Abstract: Organic crop production is increasing with consumer demand, but research is needed on the best management practices that minimize greenhouse gas (GHG) emissions. This study was conducted in central Missouri from 2012 to 2014 using a three-year rotation, consisting of corn (Zea mays L.), cereal rye cover crop (Secale cereale L.), soybean (Glycine max L.), winter wheat (Triticum aestivum L.), summer cover crop mix [Buckwheat (Fagopyrum esculentum Moench), sunn hemp (Crotalaria juncea L.), cowpea (Vigna unguiculata (L.) Walp.)], and cereal rye/hairy vetch cover crop mix (Vicia villosa L.). Treatments included tillage/cover crop practice (TCCP) combinations: 1) tillage with no cover crop (TNCC), 2) tillage with cover crop (TCC), and 3) no-till with cover crop (NTCC) and compost additions relative to the recommended rate (0x, 1x, 1.5x). Carbon dioxide (CO2) and nitrous oxide (N2O) emission measurements followed GRACEnet protocol. GHG emissions were not influenced by management practices in 2012 due to severe drought. TCCP had direct (2013 corn, 2014 soybean) or interactive (2014 wheat) effects on CO2 emissions; compost had a direct effect (2014 corn) on N2O emissions. Drought in 2012 and 2013 contributed to generally low CO2 and N2O emissions (99-2924 kg CO2-C/ha and 0-0.8 kg N2O-N/ha, respectively) while emissions increased in 2014 (527-7740 kg CO2-C/ha and <.1-10.1 kg N2O-N/ha, respectively). Across all years and crops, NTCC showed greater CO2 emissions than TNCC (1579 and 893 kg CO2-C/ha, respectively). While few treatment differences were observed, TCCP resulted in more GHG emission differences than compost rate.