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; DILORENZO, NICOLAS - University Of Florida; RUIZ-MORENO, MARTIN - University Of Florida; DANTAS, LUANA - University Of Florida; GROSSI, BRUNO - Embrapa; FARIAS, GUSTAVO - University Of Florida; Jaramillo, David; ZAGATO, LUANA - University Of Idaho; WRIGHT, DAVID - University Of Florida

Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2023
Publication Date: 8/22/2023
Citation: Santos, E., Dubeux, J., Mackowiak, C., Sollenberger, L., Dilorenzo, N., Ruiz-Moreno, M., Dantas, L., Grossi, B., Farias, G., Jaramillo, D.M., Zagato, L., Wright, D. 2023. Above and belowground litter decomposition of cover crops grazed at different intensities. Grass and Forage Science. 78(3):376-389. https://doi.org/10.1111/gfs.12617.
DOI: https://doi.org/10.1111/gfs.12617

Interpretive Summary: Grazing cover crops may increase land-use efficiency while promoting sustainable agroecosystems. 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 oat (Avena sativa), managed as follows: no grazing + 34 kg N ha-1 (NG34), no grazing + 90 kg N ha-1 (NG90), heavy grazing (HG), moderate grazing (MG), and light grazing (LG). After cover crop termination, above and belowground litter were collected and incubated in situ to estimate decomposition patterns. By day 128, NG34 had 87% of its initial aboveground biomass, whereas HG had 58%, driven by greater initial C:N ratio in NG34 than HG. Heavy grazing had lesser aboveground litter N than NG90, and lesser aboveground final N stock than NG90 and LG. Compared to aboveground, belowground litter contributed 2-fold to N deposition on average. Belowground N disappearance was greater for NG90 than NG34. Cover crops can be grazed at moderate and light intensities without affecting their performance and N supply for the following crop, while increasing land utilization and aggregating value via animal product addition.

Technical Abstract: Grazing cover crops may increase land-use efficiency while promoting sustainable agroecosystems. 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 oat (Avena sativa L.), managed as follows: no grazing + 34 kg N ha-1 (NG34), no grazing + 90 kg N ha-1 (NG90), heavy grazing (HG), moderate grazing (MG), and light grazing (LG). 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 and synchronism between N release from litter and uptake from cotton. By day 128, NG34 had 87% of its initial aboveground biomass, whereas HG had 58%, driven by greater initial C:N ratio in NG34 than HG (71 vs. 27). Heavy grazing had lesser aboveground litter N than NG90 (27 vs. 60 kg N ha-1), and lesser aboveground final N stock than NG90 and LG (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.