Articles
Nitrogen and carbon decomposition dynamics of three annual, warm season cover crop mixtures in a subtropical climate
Article number
1460_26
Pages
215 – 224
Language
English
Abstract
Plant residue from cover crops and the resulting nitrogen (N) and carbon (C) decomposition dynamics influence nutrient cycling and soil improvement potential.
Cover crop species selection, weather, and soil conditions influence the rate of residue decomposition in complex ways.
The objective of this study was to understand the decomposition dynamics of three warm season cover crops deployed as mixtures.
An in-field experiment was conducted in southwestern Florida on poorly drained sandy soils with sunn hemp (SH; Crotalaria juncea), sorghum sudangrass (SS; Sorghum bicolor × S. bicolor var. sudanese), and velvet bean (VB; Mucuna pruriens). N and C decomposition dynamics were quantified using a litter bag experiment conducted during the summer months.
After 60 days of cover crop growth, biomass was dried, placed in litter bags, and pinned on the soil surface of corresponding cover crop plots.
Litter bags were collected over 56 days to observe N and C content of residues.
Exponential decay models were generated for dry matter, N, and C. Total N decomposed from crop residue during the trial ranged from 4.2 kg N ha‑1 (VB only) to 15.3 kg N ha‑1 (SHVB mixture). Carbon decomposed ranged from 75.5 kg C ha‑1 (VB only) to 490.9 kg C ha‑1 (SHSS mixture) during the trial.
Rapid decomposition of dry matter, N, and C was observed within two weeks of termination (up to 69% N and 69% C), though residue treatments containing SS had slower rates of decomposition (as little as 15% N and 11% C) associated with lower decay rate constant (k1) values.
The highest average rate of N and C decomposition was observed in the legume-legume mixture (SHVB). This research suggests that different warm season cover crop mixtures affect the rate of residue decomposition.
Cover crop species selection, weather, and soil conditions influence the rate of residue decomposition in complex ways.
The objective of this study was to understand the decomposition dynamics of three warm season cover crops deployed as mixtures.
An in-field experiment was conducted in southwestern Florida on poorly drained sandy soils with sunn hemp (SH; Crotalaria juncea), sorghum sudangrass (SS; Sorghum bicolor × S. bicolor var. sudanese), and velvet bean (VB; Mucuna pruriens). N and C decomposition dynamics were quantified using a litter bag experiment conducted during the summer months.
After 60 days of cover crop growth, biomass was dried, placed in litter bags, and pinned on the soil surface of corresponding cover crop plots.
Litter bags were collected over 56 days to observe N and C content of residues.
Exponential decay models were generated for dry matter, N, and C. Total N decomposed from crop residue during the trial ranged from 4.2 kg N ha‑1 (VB only) to 15.3 kg N ha‑1 (SHVB mixture). Carbon decomposed ranged from 75.5 kg C ha‑1 (VB only) to 490.9 kg C ha‑1 (SHSS mixture) during the trial.
Rapid decomposition of dry matter, N, and C was observed within two weeks of termination (up to 69% N and 69% C), though residue treatments containing SS had slower rates of decomposition (as little as 15% N and 11% C) associated with lower decay rate constant (k1) values.
The highest average rate of N and C decomposition was observed in the legume-legume mixture (SHVB). This research suggests that different warm season cover crop mixtures affect the rate of residue decomposition.
Authors
S.M. Swartz, Z.T. Brym, T.N. Motis
Keywords
crop residue management, subtropical, agroecology, underutilized plant species
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