Pursuing robust agroecosystem functioning through effective soil organic carbon management

2020

Agronomy Journal

Production of corn (Zea mays L.) requires significant N availability to reach maximum yield potential. Nitrogen fertilizer recommendations generally have ignored sitespecific conditions and have focused more on total N demand for representative soils across a region. Recent evidence suggested that site-specific conditions of the biologically active component (0-10-cm depth) could inform the magnitude of yield response to applied N fertilizer. This approach was tested further on 111 fields in Coastal Plain, Piedmont, and Blue Ridge regions (states of North Carolina, South Carolina, and Virginia). Plant-available N (sum of residual inorganic N and net N mineralization during a 24-d aerobic incubation) was inversely proportional to economically optimum N rate scaled to grain production level (r 2 = .47, p < .001). Soil-test biological activity as a simple, rapid, and reliable indicator of net N mineralization was also predictive of economically optimum N rate (r 2 = .46, p < .001) and validated an earlier assessment. Greater soil-test biological activity was obtained from private farms than from research stations (259 vs. 172 mg C kg −1 3 d −1 , respectively; p < .001), as well as from fields with minimum tillage, multi-species cover cropping, and amendment with animal manures. Results imply that some farmers are making choices to improve soil health condition and these choices can lead to lower requirement for N fertilizer inputs.

Section: Resultsmentioning

confidence: 99%

Soil‐test biological activity with the flush of CO₂: V. Validation of nitrogen prediction for corn production

2020

Agronomy Journal

“…However, because a nonlinear depth distribution was expected in all soil types investigated here, appropriately averaged estimation of SOC concentration with depth was still expected. It should be noted that Spodosols with significant leaching and precipitation of SOC at depth are soil types not well described by this nonlinear depth distribution function (Franzluebbers, 2013).…”

Section: Soc Stock Estimationmentioning

confidence: 95%

Root‐zone soil organic carbon enrichment is sensitive to land management across soil types and regions

Soil Science Soc of Amer J

2021

Measuring and monitoring changes in soil organic C (SOC) concentrations and stocks are important for understanding ecosystem functions. Sequestration of SOC has traditionally been measured from resource-intensive studies over extended periods of time, but an alternative approach of calculating root-zone SOC enrichment is described here as a proxy for estimating SOC sequestration using nonlinear distribution of SOC concentration in the surface 30 cm. From literature data across 52 studies, estimated SOC concentration at 30-cm depth was not different between pairs of conservation management and conventional-till cropland, suggesting support for the concept of using SOC concentration at 30-cm depth as a baseline concentration from which enrichment can be calculated. Root-zone SOC enrichment across this (n = 420) and an earlier study (n = 171) was 12.0 ± 0.6 Mg C ha -1 (mean ± SE) under conventional-till cropland (n = 209), 16.1 ± 0.6 Mg C ha -1 under no-till cropland (n = 269), 20.6 ± 1.0 Mg C ha -1 under grassland (n = 90), and 25.8 ± 3.8 Mg C ha -1 under woodland (n = 23). Regional climatic conditions and soil texture were important in influencing baseline SOC storage and total SOC stock but were minor factors in affecting root-zone SOC enrichment with conservation management. Rootzone SOC enrichment is a relatively simple and straightforward calculation method to indicate SOC sequestration, and if deployed across a diversity of management and farm locations, could lead to better SOC stock inventories and analyses of how contemporary management influences SOC stock change in different ecoregions. INTRODUCTIONSoil organic C (SOC) is a key ecosystem attribute that affects agricultural productivity and controls a wide range of ecosystem processes, including greenhouse gas fluxes, nutrient cycling, and water infiltration and retention (Lehmann et al., 2020). Because of its contribution to the performance of these Abbreviations: BD, bulk density; SOC, soil organic carbonThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

“…This assumption may not be valid in saturated soils with variable organic deposition and migration of organic matter with Fe and Al (e.g. Histosols or Spodosols) (Franzluebbers, 2013). The hypothesis was that SOC sequestration could be calculated from a SOC stock change minus that of an assumed baseline condition, determined for each soil profile from SOC concentration immediately below the zone of tillage influence (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Soil‐profile data from several published studies were assembled to make calculations and compare results with more standard approaches to calculation of SOC sequestration. Mathematical description of SOC depth distribution was presented before (Franzluebbers, 2013), but the approach of calculating SOC sequestration based on an internal soil‐profile reference condition is novel and developed here for potential further use.…”

Section: Introductionmentioning

confidence: 99%

“…This was the premise of this study that SOC concentration immediately below the zone of tillage influence could be used as a baseline condition to which SOC concentrations nearer the surface could be compared. This assumption may not be valid in saturated soils with variable organic deposition and migration of organic matter with Fe and Al (e.g., Histosols or Spodosols) (Franzluebbers, 2013). The hypothesis was that SOC sequestration could be calculated from a SOC stock change minus that of an assumed baseline condition, determined for each soil profile from SOC concentration immediately below the zone of tillage influence (i.e., at 30‐cm depth).…”

Section: Introductionmentioning

confidence: 99%

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Soil organic carbon sequestration calculated from depth distribution

Soil Science Soc of Amer J

2021

Sequestration of organic C in agricultural soils is necessary to improve soil health to meet the challenges of climate change, diminishing biodiversity, water quality deterioration, and rising demands for food and fiber production. New assessment approaches are needed to quantify how conservation agriculture might contribute to soil health improvement and soil organic C (SOC) sequestration. In the southeastern US, conservation management has been repeatedly shown to stratify SOC concentration with depth. Starting immediately below a zone of tillage influence (i.e. 30-cm depth), SOC concentration is rarely affected by management due to low C inputs and high decomposition potential, while concentration increases toward the surface in a non-linear manner, presumably with greater inputs of residue and root inputs and changing temperature and moisture conditions. Using these observations as an ecological foundation, SOC sequestration was calculated as the summation of SOC stock greater than the baseline condition at 30-cm depth. Data from literature sources were mathematically fitted with this new approach as a validation. Two on-farm surveys with different agricultural management practices (5-40 yr) in the southeastern US yielded preliminary estimates of SOC sequestration. The interquartile range of calculated SOC sequestration was 4.2 to 9.4 Mg C ha-1 for conventional-tillage cropland (n = 45 fields), 13.6 to 29.7 Mg C ha-1 for no-tillage cropland (n = 97 fields), and 15.9 to 26.1 Mg C ha-1 for perennial pasture (n = 29 fields).