Above and belowground litter decomposition of cover crops grazed at different intensities

Authors: SANTOS, ERICK - University Of Florida; DUBEUX, JOSE - University Of Florida; MACKOWIAK, CHERYL - University Of Florida; SOLLENBERGER, LYNN - University Of Florida; WRIGHT, DAVID - University Of Florida; DILORENZO, NICOLAS - University Of Florida; ZAGATO, LUANA - University Of Florida; FARIAS, GUSTAVO - University Of Florida; QUEIROZ, LUANA - University Of Florida; Jaramillo, David; RUIZ-MORENO, MARTIN - University Of Florida

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/12/2021
Publication Date: 11/12/2021
Citation: Santos, E., Dubeux, J., Mackowiak, C., Sollenberger, L., Wright, D., Dilorenzo, N., Zagato, L., Farias, G., Queiroz, L., Jaramillo, D.M., Ruiz-Moreno, M. 2021. Above and belowground litter decomposition of cover crops grazed at different intensities. Meeting Abstract. ASA, CSSA, SSSA International Annual Meeting, Salt Lake City, UT.

Interpretive Summary: Grazing cover crops may increase land-use efficiency while promoting sustainability. We investigated how grazing intensity affects cover crop litter quantity, quality, decomposition, and the effect on cotton (Gossypium hirsutum ) N removal. Cover crops were a mixture of rye (Secale cereale) and oats (Avena sativa), managed as follows: no grazing + N ha-1 (NG34), no grazing + 90 kg N ha-1 (NG90), overgrazing (OG), moderate grazing (MG), and undergrazing (UG). By day 128, NG34 had 87% of its initial aboveground biomass, whereas OG had 58%, driven by greater initial C:N ratio in NG34 than OG (71 vs 27). Overgrazing had lesser aboveground litter N than NG90 (27 vs 60 kg N ha-1), and lesser aboveground final N stock than NG90 and UG (16 vs 47 and 41 kg N ha-1). Compared to aboveground, belowground litter contributed 2-fold to N deposition on average. Belowground N disappearance was greater for NG90 than NG34. Cotton N removal at day 128 was similar across treatments. Cover crops can be grazed at moderate and light intensities without affecting their performance and N supply for the following crop.

Technical Abstract: Grazing cover crops may increase land-use efficiency while promoting sustainability. We investigated how grazing intensity affects cover crop litter quantity, quality, decomposition, and the effect on cotton (Gossypium hirsutum L.) N removal. Cover crops were a mixture of rye (Secale cereale L.) and oats (Avena sativa L.), managed as follows: no grazing + 34 kg N ha-1 (NG34), no grazing + 90 kg N ha-1 (NG90), overgrazing (OG), moderate grazing (MG), and undergrazing (UG). Grazed treatments received 90 kg N ha-1. After cover crop termination, above and belowground litter were collected and incubated in situ to estimate decomposition patterns. Samples were removed after 0, 4, 8, 16, 32, 64, and 128 incubation days concomitant with cotton plants used to estimate N removal. By day 128, NG34 had 87% of its initial aboveground biomass, whereas OG had 58%, driven by greater initial C:N ratio in NG34 than OG (71 vs 27). Overgrazing had lesser aboveground litter N than NG90 (27 vs 60 kg N ha-1), and lesser aboveground final N stock than NG90 and UG (16 vs 47 and 41 kg N ha-1). Compared to aboveground, belowground litter contributed 2-fold to N deposition on average (46 vs 98 kg N ha-1). Belowground N disappearance was greater for NG90 than NG34 (39 vs 21 kg N ha-1). Cotton N removal at day 128 was similar across treatments (191 kg N ha-1). Cover crops can be grazed at moderate and light intensities without affecting their performance and N supply for the following crop.