Fertoz : Cover Cropping to Enhance Carbon Sequestration in Agriculture

Benefits of Cover crops

As global attitudes shift towards adopting environmentally sustainable production practices to mitigate climate change, cover cropping can play a meaningful role in improving soil health by returning CO₂ from the atmosphere to the soil. Cover crops (or catch crops) provide multiple benefits that can improve soil productivity. They provide organic matter full of carbon (C) and nitrogen (N) which can increase soil water holding capacity, porosity, aggregate stability, nutrient cycling, and microbial activity^12,19,28, as well as reduce erosion, disease pressure, pest pressure and nitrogen leaching, and fix atmospheric nitrogen and sequester carbon^{1,2,4,6,9,16,20,25,31,38,41,44}. Increasing the quantity and quality of plant biomass returns with favorable soil conditions for incorporation can increase soil organic carbon.

What are Cover Crops?

Cover crops are typically planted in the fallow period between cash crops. The cover crop provides a vegetative cover over the soil which protects it from erosion and reduces nitrate leaching⁴⁸. They are typically produced in the fall and early spring when low temperature and light availability are likely to promote high ratios of root to shoot production³⁰. Deeper cover crop roots can provide deeper delivery of carbon into the soil profile¹. Cover cropping can utilize a single species or a mixture of species and can be annual, biennial or perennial vegetation¹. They can be ploughed‐in during the winter or spring or grazed then incorporated in soils by tillage to prevent competition with the primary crop, and to promote mineralization of organic N^1,11. Most cover crops do not reach maturity, therefor are not harvested. Their residues are left to decompose in the field adding C and N to the soil, especially when legumes are added into a rotation^{6,7,9,11,13,18,20,22,24,31,39,45,47}.

Quantifying the Correlation Between Cover Cropping and Enhanced Carbon Sequestration

The following table displays a summary of some of the carbon sequestration potentials observed by other studies using various cover cropping strategies. These numbers show an increase in total soil carbon from the use of cover crops compared to cropping systems without cover crops (expressed in percentage increase or added tonnes per hectare per year).

This C sequestration potential varies with different soil, climate, and management conditions. Studies suggest that overall cover crop biomass is the main driver of soil C accumulation whereas others suggest the importance of using cover crop combinations that use both legumes and nonlegumes^{14,26,42,43,50}. Mcdaniel et al. (2014) found legumes to be an important cover crop for soil C accumulation across a wide variety of rotations, soil types, and climates.

Crop Types and Functions

It is important to consider the cover crop best suited for a crop rotation as well as timely seeding to maximize vegetative growth of the cover crop while minimizing competition with the subsequent cash crop. Different cover crops can be used for different purposes in a field and can be divided into four categories: legumes (e.g. alfalfa, vetches, and clover), non‐legumes (spinach, and flax), grasses (e.g. ryegrass and barley) and brassicas (e.g. canola, radishes, turnips)¹.

In soils where nitrogen (N) is limiting, legume crops can improve soil nutrition by not only adding organic matter, but by fixing atmospheric N which is added to the soil for use by subsequent cash crops²⁹.

Conversely, non-legume cover crops that are higher in carbon can be used to absorb excess nitrate from the soil which reduces nitrate leaching as well as increases green manure biomass^3,15,24,40. Brassica species with deep taproots like radish or rapeseed can be used to alleviate soil compaction as they break through compacted soil²⁵. Maize yields have been reported to have increased following radish or rapeseed cover crops due to reduced compaction and increased access to water at lower depths, overall increasing drought resistance⁹. Furthermore, C sequestration can be increased by combining cover crop rotations with minimal or zero-till practices due to reduced soil disturbance^21,32-37,49.

Current Opportunities for Growers

Producers implementing a cover crop strategy for reducing their carbon footprint can generate carbon offsets through scope 1 voluntary carbon offset protocols. Alfalfa is a great example of a cover crop that can be seeded to increase carbon sequestration potential and create on farm carbon offsets. Legumes are very effective nitrogen fixers; when added to the rotation as a cover crop, can provide additional N to the cash crop, reducing high nitrogen fertilizer requirements, enhancing nitrogen use efficiencies, and mitigating runoff and leaching losses. Nitrous oxide emissions reductions protocols (NERP) are available for producers managing their nitrogen according to sustainable 4R nutrient management practices to generate carbon offset credits that can then be traded in the carbon market for revenue.

Contact Fertoz to stay up to date on current and upcoming carbon opportunities.

Stephen Froese

Phone number: 306-202-9383

Email: [email protected]

www.fertoz.com

References

1. Abdalla, M., Hastings, A., Cheng, K., Yue, Q., Chadwick, D., Espenberg, M., Truu, J., Rees, R.M. Smith, P. 2019. A critical review of the impacts of cover crops on nitrogen leaching, net greenhouse gas balance and crop productivity. Glob Change Biol. 25:2530-2543. DOI: 10.1111/gcb.14644
2. Alcantara, C., Pujadas, A., Saavedra, M., 2011. Management of cruciferous cover crops by mowing for soil and water conservation in southern Spain. Agric. Water Manag. 98:1071-1080.
3. Basche, A., Miguez, F.E., Kaspar, T., Castellano, M.J. 2014. Do cover crops increase or decrease nitrous oxide emissions? A meta-analysis. J Soil Water Conserv 69:471-482. doi:10.2489/jswc.69.6.471
4. Battany, M., & Grismer, M. E. 2000. Rainfall runoff and erosion in Napa Valley vineyards: Effects of slope, cover and surface roughness. Hydrological Processes, 14:1289-1304. https ://doi.org/10.1002/ (sici)1099‐1085(20000 5)14:7<1289::aid‐hyp43 >3.0.co;2‐r
5. Bruce, J. P., Frome,M., Haites, E., Janzen, H., Lal, R., and Paustian, K.: 1999, 'Carbon Sequestration in Soils', J. Soil Water Conserv. 54, 382-389.
6. Campbell, C. A., Bierderbeck, V. O., Zentner, R. P., and Lafond, G. P. 1991. 'Effect of Crop Rotations and Cultural Practicies on Soil Organic Matter, Microbial Biomass and Respiration in a Thin Black Chernozem', Can. J. Soil Sci. 71:363-376.
7. Carranca, C., Oliveira, A., Pampulha, E., and Torres, M.O. 2009. Temporal dynamics of soil nitrogen, carbon and microbial activity in conservative and disturbed fields amended with mature white lupine and oat residues. Geoderma 151:50-59.
8. Chen, G., Weil, R.R. 2011. Root growth and yield of maize as affected by soil compaction and cover crops. Soil Tillage Res 117:17-27. doi:10.1016/j.still.2011.08.001
9. Collins, H. P., Rasmussen, P. E., and Douglas, C. L. Jr. 1992, 'Crop Rotation and Residue Management Effects on Soil Carbon and Microbial Dynamics', Soil Sci. Soc. Am. J. 56:783-788.
10. Dabney, S. M., Delgado, J. A., Meisinger, J. J., Schomberg, H. H., Liebig, M. A., Kaspar, T., Reeves, W. 2011. Using cover crops and cropping systems for nitrogen management. In J. A. Delgado & R. F. Follet (Eds.), Advances in nitrogen management for water quality (pp. 230- 281). Ankeny, IA: Soil and Water Conservation Society.
11. Don, A., Schumacher, J., Freibauer, A., 2011. Impact of tropical land-use change on soil organic carbon stocks - a meta-analysis. Global Change Biology 17:1658-1670. https://doi.org/10.1111/j.1365-2486.2010.02336.x.
12. Drinkwater, L. E., & Snapp, S. S. 2007. Nutrients in agroecosystems: Rethinking the management paradigm. Advances in Agronomy, 92:63-186. https ://doi.org/10.1016/s0065‐2113(04)92003‐2
13. Drinkwater, L. E., Wagoner, P., and Sarrantonio, M. 1998. Legume-based cropping systems have reduced carbon and nitrogen losses. Nature 396:262-265
14. Fageria, N. K., Baligar, V.C., and Bailey, B.A. 2005. Role of cover crops in improving soil and row crop productivity. Communications in Soil Science and Plant Analysis 36:2733- 2757.
15. Finney, D. M., White, C. M., & Kaye, J. P. 2016. Biomass production and carbon/nitrogen ratio influence ecosystem services from cover crop mixtures. Agronomy Journal, 108(1):39-52. https ://doi.org/10.2134/ agron j15.0182
16. Follett, R.F. 2001. Soil management concepts and carbon sequestration in crop land soils. Soil Tillage Res. 61:77-92.
17. Follett, R. F., Kimble, J. M., and Lal, R. 2001. 'The Potential of U.S. Grazing Lands to Sequester Soil Carbon', in Follett, R. F., Kimble, J. M., and Lal, R. (eds.), The Potential of U.S. Grazing Lands to Sequester Carbon and Mitigate the Greenhouse Effect, Lewis Publishers, Boca Raton, FL, pp. 401-430.
18. Grandy, A., and Robertson, G. 2007. Land-use intensity effects on soil organic carbon accumulation rates and mechanisms. Ecosystems 10:59-74.
19. Harunaa, S. I., & Nkongolo, N. V. 2015. Cover crop management effects on soil physical and biological properties. Procedia Environmental Sciences, 29:13-14. https ://doi.org/10.1016/j. proenv.2015.07.130
20. Hu, S., Grunwald, N. J., van Bruggen, A. H. C., Gamble, G. R., Drinkwater, L. E., Shennan, C., and Demment, M. W. 1997. 'Short-Term Effects of Cover Crop Incorporation on Soil Carbon Pools and Nitrogen Availability'. Soil Sci. Soc. Am. J. 61:901-911.
21. Hubbard, R. K., Strickland, T. C., & Phatak, S. 2013. Effects of cover crop systems on soil physical properties and carbon/nitrogen relationships in the coastal plain of southeastern USA. Soil and Tillage Research, 126:276-283. https://doi.org/10.1016/j.still.2012.07.009
22. Jarecki, M. K., and R. Lal. 2003. Crop management for soil carbon sequestration. Critical Reviews in Plant Sciences 22:471-502.
23. Jian, J., Du, X., Reiter, M. S., & Stewart, R. D. 2020. A meta-analysis of global cropland soil carbon changes due to cover cropping. Soil Biology and Biochemistry, 143. https://doi.org/10.1016/j.soilbio.2020.107735
24. Kaspar, T. C., & Singer, J. W. 2011. The use of cover crops to manage soil. In J. L. Hatfield & T. J. Sauer (Eds.), Soil management: Building a stable base for agriculture (pp. 321-337). Madison, WI: American Society of Agronomy and Soil Science Society of America Journal.
25. Kaye, J.P., and Quemada, M. 2017. Using cover crops to mitigate and adapt to climate change. A review. Agron. Sustain. Dev. 37: 4 DOI 10.1007/s13593-016-0410-x
26. Kuo, S., Sainju, U.M., and Jellum, E.J. 1997. Winter cover crop effects on soil organic carbon and carbohydrate in soil. Soil Science Society of America Journal 61:145-152.
27. Lal, R., Kimble, J., Follett, R. F., and Cole, C. V.: 1998, The Potential for U.S. Cropland to Sequester Carbon and Mitigate the Greenhouse Effect, Sleeping Bear Press, Ann Arbor, MI, 128 pp.
28. Lotter, D. W., Seidel, R., & Liebhardt, W. 2003. The performance of or‐ ganic and conventional cropping systems in an extreme climate year. American Journal of Alternative Agriculture, 18:146-154. https ://doi. org/10.1079/ajaa2 00345
29. Lüscher, A., Mueller‐Harvey, I., Soussana, J. F., Rees, R. M., & Peyraud, J. L. 2014. Potential of legume‐based grassland‐livestock systems in Europe: A review. Grass Forage Science, 69(2):206-228. https ://doi. org/10.1111/gfs.12124
30. Marcelis, L. F. M., Heuvelink, E., and Goudriaan, J. 1998. Modelling biomass production and yield of horticultural crops: a review. Scientia Horticulturae 74:83-111.
31. McDaniel, M., Tiemann, L., Grandy, A.S. 2014. Does agricultural crop diversity enhance soil microbial biomass and organic matter dynamics? A meta-analysis. Ecol Appl 24:560-570. doi:10.1890/13- 0616.
32. Mitchell, J.P., Munk, D.S., Prys, B., Klonsky, K.K., Wroble, J.F., DeMoura, R.L., 2006. Conservation tillage cotton production systems in the San Joaquin Valley. Calif. Agric. 60(3):140-145.
33. Mitchell, J.P., Klonsky, K., Shrestha, A., Fry, R., DuSault, A., Beyer, J., Harben, R. 2007. Adoption of conservation tillage in California: current status and future perspectives. Aust. J. Exp. Agric. 47(12):1383-1388.
34. Mitchell, J.P., Southard, R.J., Madden, N.M., Klonsky, K.M., Baker, J.B., DeMoura, R.L., Horwath, W.R., Munk, D.S., Wroble, J.F., Hembree, K.J., Wallender, W.W. 2008. Transition to conservation tillage evaluated in San Joaquin Valley cotton and tomato rotations. Calif. Agric. 62(2):74-79.
35. Mitchell, J.P., Pettygrove, G.S., Upadhyaya, S., Shrestha, A., Fry, R., Roy, R., Hogan, P., Vargas, R., Hembree, K., 2009. Classification of Conservation Tillage Practices in California Irrigated Row Crop Systems. UC ANR Communication Services Publication 8364.
36. Mitchell, J.P., Shrestha, A., Horwath, W.R., Southard, R.J., Madden, N.M., Veenstra, J., Munk, D.S., 2015. Tillage and cover cropping affect crop yields and soil carbon in the San Joaquin Valley. Calif. Agron. J. 107:588-596.
37. Mitchell, J. P., Shrestha, A., Mathesius, K., Scow, K. M., Southard, R. J., Haney, R. L., Horwath, W. R. 2017. Cover cropping and no-tillage improve soil health in an arid irrigated cropping system in California's San Joaquin Valley, USA. Soil and Tillage Research, 165:325-335. https://doi.org/10.1016/j.still.2016.09.001
38. Poeplau, C., & Don, A. 2015. Carbon sequestration in agricultural soils via cultivation of cover crops - A meta-analysis. Agriculture, Ecosystems and Environment, 200:33-41. https://doi.org/10.1016/j.agee.2014.10.024
39. Poeplau, C., Don, A., Vesterdal, L., Leifeld, J., Van Wesemael, B., Schumacher, J., Gensior, A. 2011. Temporal dynamics of soil organic carbon after land-use change in the temperate zone - carbon response functions as a model approach. Global Change Biology 17:2415-2427. https://doi.org/10.1111/j.1365-2486.2011.02408.x.
40. Quemada, M., Baranski, M., Nobel‐de Lange, M. N. J., Vallejo, A., & Cooper, J. M. 2013. Meta‐analysis of strategies to control nitrate leaching in irrigated agricultural systems and their effects on crop yield. Agriculture, Ecosystems and Environment, 174:1-10. https ://doi. org/10.1016/j.agee.2013.04.018
41. Ruiz-Colmenero, M., Bienes, R., Marques, M.J. 2011. Soil and water conservation dilemmas associated with the use of green cover in steep vineyards. Soil Tillage Res. 117:211-223.
42. Sainju, U., Singh, B. & Whitehead, W. 2002. Long-term effects of tillage, cover crops, and nitrogen fertilization on organic carbon and nitrogen concentrations in sandy loam soils in Georgia, USA. Soil and Tillage Research, 63:167-179. DOI: 10.1016/S0167-1987(01)00244-6
43. Sainju, U.M., Singh, B.P., Whitehead, W.F., Wang, S. 2006. Carbon supply and storage in tilled and nontilled soils as influenced by cover crops and nitrogen fertilization. J. Environ. Qual. 35:1507. https://doi.org/10.2134/jeq2005.0189.
44. Schipanski, M.E., Barbercheck, M., Douglas, M.R., Finney, D.M., Haider, K., Kay, J.P., Kemanian, A.R., Mortensen, D.A., Ryan, M.R., Tooker, J., White, C. 2014. A framework for evaluating ecosystem services provided by cover crops in agroecosystems. Agric. Syst. 125:12-22.
45. Spehn, E. M., Joshi, J., Schmid, B., Alphei, J., and Korner, C. 2000. Plant diversity effects on soil heterotrophic activity in experimental grassland ecosystems. Plant and Soil 224:217- 230.
46. Sperow, M., Eve, M., & Paustian, K. 2003. Potential soil c sequestration on U.S. Agricultural soils. Climatic Change 57:319-339.
47. Steenwerth, K., & Belina, K. M. 2008. Cover crops and cultivation: Impacts on soil N dynamics and Micro‐biological function in a Mediterranean vineyard agroecosystem. Applied Soil Ecology, 40:370-380. https ://doi.org/10.1016/j.apsoil.2008.06.004
48. Troeh, F. R., Hobbs, J. A., and Donahue, R. L. 1991. Soil and Water Conservation, Prentice Hall, Englewood Cliffs, NJ. 530 pp.
49. Veenstra, J., Horwath, W.R., Mitchell, J.P., Munk, D.S. 2007. Tillage and cover cropping effects on aggregate-protected carbon in cotton and tomato. Soil Sci. Soc. Am. J. 326-371. doi:http://dx.doi.org/10.2136/sssaj2006.0229.
50. Villamil, M. B., Bollero, G. A., Darmody, R. G., Simmons, F.W., and Bullock, D.G. 2006. No-till corn/soybean systems including winter cover crops. Soil Science Society of America Journal 70:1936-1944.