scholarly journals Greater soil carbon stocks and faster turnover rates with increasing agricultural productivity

2016 ◽  
Author(s):  
Jonathan Sanderman ◽  
Courtney Creamer ◽  
W. Troy Baisden ◽  
Mark Farrell ◽  
Stewart Fallon

Abstract. Devising agricultural management schemes that enhance food security and soil carbon levels is a high priority for many nations. However, the coupling between agricultural productivity, soil carbon stocks and organic matter turnover rates is still unclear. Archived soil samples from four decades of a long-term crop rotation trial were analysed for soil organic matter (SOM) cycling relevant properties: C and N content, bulk composition by NMR spectroscopy, amino sugar content, short term C bioavailability assays, and long-term C turnover rates by modeling the incorporation of the bomb-spike in atmospheric 14C into the soil. After > 40 years under consistent management, topsoil carbon stocks ranged from 14 to 33 Mg C ha−1 and were linearly related to the mean productivity of each treatment. Measurements of SOM composition demonstrated increasing amounts of plant- and microbially-derived SOM along the productivity gradient. Under two modelling scenarios, radiocarbon data indicated overall SOM turnover time decreased from 40 to 13 years with increasing productivity; twice the rate of decline predicted from simple steady-state models or static three-pool decay rates of measured C pool distributions. Similarly, the half-life of synthetic root exudates decreased from 30.4 to 21.5 hours with increasing productivity indicating accelerated microbial activity. These findings suggest that there is a direct feedback between accelerated biological activity, carbon cycling rates and rates of carbon stabilization with important implications for how SOM dynamics are represented in models.

SOIL ◽  
2017 ◽  
Vol 3 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Jonathan Sanderman ◽  
Courtney Creamer ◽  
W. Troy Baisden ◽  
Mark Farrell ◽  
Stewart Fallon

Abstract. Devising agricultural management schemes that enhance food security and soil carbon levels is a high priority for many nations. However, the coupling between agricultural productivity, soil carbon stocks and organic matter turnover rates is still unclear. Archived soil samples from four decades of a long-term crop rotation trial were analyzed for soil organic matter (SOM) cycling-relevant properties: C and N content, bulk composition by nuclear magnetic resonance (NMR) spectroscopy, amino sugar content, short-term C bioavailability assays, and long-term C turnover rates by modeling the incorporation of the bomb spike in atmospheric 14C into the soil. After > 40 years under consistent management, topsoil carbon stocks ranged from 14 to 33 Mg C ha−1 and were linearly related to the mean productivity of each treatment. Measurements of SOM composition demonstrated increasing amounts of plant- and microbially derived SOM along the productivity gradient. Under two modeling scenarios, radiocarbon data indicated overall SOM turnover time decreased from 40 to 13 years with increasing productivity – twice the rate of decline predicted from simple steady-state models or static three-pool decay rates of measured C pool distributions. Similarly, the half-life of synthetic root exudates decreased from 30.4 to 21.5 h with increasing productivity, indicating accelerated microbial activity. These findings suggest that there is a direct feedback between accelerated biological activity, carbon cycling rates and rates of carbon stabilization with important implications for how SOM dynamics are represented in models.


2015 ◽  
Vol 127 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Oliva Pisani ◽  
Lisa H. Lin ◽  
Olivia O. Y. Lun ◽  
Kate Lajtha ◽  
Knute J. Nadelhoffer ◽  
...  

2007 ◽  
Vol 81 (2) ◽  
pp. 145-155 ◽  
Author(s):  
Thomas Kätterer ◽  
Liselotte Andersson ◽  
Olof Andrén ◽  
Jan Persson

2020 ◽  
Author(s):  
Victoria Janes-Bassett ◽  
Jessica Davies ◽  
Richard Bassett ◽  
Dmitry Yumashev ◽  
Ed Rowe ◽  
...  

<p>Throughout the Anthropocene, the conversion of land to agriculture and atmospheric deposition of nitrogen have resulted in significant changes to biogeochemical cycling, including soil carbon stocks. Quantifying these changes is complex due to a number of influential factors (including climate, land use management, soil type) and their interactions. As the largest terrestrial store of carbon, soils are a key component in climate regulation. In addition, soil carbon storage contributes to numerous ecosystem services including food provision. It is therefore imperative that we understand changes to soil carbon stocks, and provide effective strategies for their future management.</p><p>Modelling soil systems provides a means to estimate changes to soil carbon stocks. Due to linkages between the carbon cycle and other major nutrient cycles (notably nitrogen and phosphorus which often limit the productivity of ecosystems), models of integrated nutrient cycling are required to understand the response of the carbon cycle to global pressures. Simulating the impacts of land use changes requires capacity to model both semi-natural and intensive agricultural systems.</p><p>In this study, we have developed an integrated carbon-nitrogen-phosphorus model of semi-natural systems to include representation of both arable and grassland systems, and a range of agricultural management practices. The model is applicable to large spatial scales, as it uses readily available input data and does not require site-specific calibration.  After being validated both spatially and temporally using data from long-term experimental sites across Northern-Europe, the model was applied at a national scale throughout the United Kingdom to assess the impacts of land use change and management practices during the last two centuries. Results indicate a decrease in soil carbon in areas of agricultural expansion, yet in areas of semi-natural land use, atmospheric deposition of nitrogen has resulted in increased net primary productivity and subsequently soil carbon. The results demonstrate anthropogenic impacts on long-term nutrient cycling and soil carbon storage, and the importance of integrated nutrient cycling within models.</p>


Geoderma ◽  
2008 ◽  
Vol 145 (1-2) ◽  
pp. 121-129 ◽  
Author(s):  
K. Denef ◽  
C.E. Stewart ◽  
J. Brenner ◽  
K. Paustian

2020 ◽  
Author(s):  
Moritz Mohrlok ◽  
Victoria Martin ◽  
Niel Verbrigghe ◽  
Lucia Fuchslueger ◽  
Christopher Poeplau ◽  
...  

<p>Soils store more carbon than the atmosphere and total land plant biomass combined. Soil organic matter (SOM) can be classified into different physical pools characterized by their degree of protection and turnover rates. Usually, these pools are isolated by dividing soils in different water-stable aggregate size classes and, inside these classes, SOM fractions with differing densities and properties: Stable mineral-associated organic matter (MOM) and labile particulate organic matter (POM). Increasing temperatures are known to initially enhance microbial decomposition rates, releasing C from soils which could further accelerate climate change. The magnitude of this feedback depends on which C pool is affected the most by increased decomposition. Since MOM, thought to be the best protected carbon pool, holds most of the soil C, losses from this pool would potentially have the biggest impact on global climate. Experimental results are inconclusive so far, as most studies are based on short-term field warming (years rather than decades), leaving the ecosystem response to decades to century of warming uncertain.</p><p>We made use of a geothermal warming platform in Iceland (ForHot; https://forhot.is/) to compare the effect of short-term (STW, 5-8 years) and long-term (LTW, more than 50 years) warming on soil organic carbon and nitrogen (SOC, SON) and its carbon and nitrogen isotope composition (δ<sup>13</sup>C and δ<sup>15</sup>N) in soil aggregates of different sizes in a subarctic grassland. OM fractions were isolated via density fractionation and ultrasonication both in macro- and microaggregates: Inter-aggregate free POM (fPOM), POM occluded within aggregates (iPOM) and MOM.</p><p>MOM, containing most of the SOC and SON, showed a similar response to warming for both macro- and microaggregates. Compared to LTW plots, STW plots overall had higher C and N stocks. But warming reduced the carbon content more strongly in STW plot than in LTW plots. δ<sup>13</sup>C of MOM soil increased with temperature on the STW sites, indicating higher overall SOM turnover rates at higher temperatures, in line with the higher SOC losses. For LTW, δ<sup>13</sup>C decreased with warming except for the most extreme treatment (+16°C). Warming duration had no impact on iPOM-C. fPOM-C decreased in STW sites with increasing temperature, while it increased on the LTW sites.</p><p>Overall our results demonstrate warming-induced C losses from the MOM-C-pool, thought to be most stable soil carbon pool. Thus, warming stimulated microbes to decompose both labile fPOM and more stable MOM. After decades of warming, C losses are less pronounced compared to the short-term warmed plots, pointing to a replenishment of the carbon pools at higher temperatures in the long-term. This might be explained by adaptations of the primary productivity and/or substrate-limitation of microbial growth.</p><p> </p>


2011 ◽  
Vol 75 (1) ◽  
pp. 226-234 ◽  
Author(s):  
A. J. VandenBygaart ◽  
E. Bremer ◽  
B. G. McConkey ◽  
B. H. Ellert ◽  
H. H. Janzen ◽  
...  

Revista CERES ◽  
2018 ◽  
Vol 65 (4) ◽  
pp. 373-380 ◽  
Author(s):  
Marihus Altoé Baldotto ◽  
Lílian Estrela Borges Baldotto

ABSTRACT Once it is stabilized in the soil, organic matter minimizes limitations of Brazilian Oxisols, such as low cation exchange capacity, low nutrient availability, toxicity due to high aluminum content, and phosphate adsorption. Moreover, humified organic matter fractions are bioactive. It is, therefore, important to evaluate the biostimulant ability of compounds present in soil carbon stocks to develop sustainable technologies for tropical agriculture based on renewable natural resources. The objective of this research was to correlate some soil quality indicators, redox properties, and bioactivity of humic acids isolated from integrated farming, livestock, and forestry systems aiming to understand the mechanisms involved in plant stimulation by humified organic matter. Carbon stocks and their stability were determined from oxidation by dichromatometry and iodometry, respectively. Bioactivity was assessed using yield data of corn indicator plants. The results indicated that when native-like forests were reintroduced instead of pastureland, soil carbon stocks and their stability increased along with overall improvements in soil fertility, chemical and physical properties, and soil biodiversity. The bioactivity of humic substances isolated from soils used in integrated crop, livestock, and forestry management was higher than that of soils derived from pastures or eucalyptus alone.


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