Can Land Management Enhance Soil Carbon Sequestration?

See published paper: "Effects of Organic Matter Amendments On Net primary Productivity and Greenhouse Gas Emission in Annual Grasslands"  Ecological Application, 23(1), 46-59 >>

Research Team

Rebecca Ryals and Whendee L. Silver (Ecosystem Sciences Division, Department of Environmental Science, Policy, and Management University of California at Berkeley).

Methods

Experimental design using two rangelands (a valley grassland and a coastal grassland), with untreated controls and treatment sites with a single application of ½ inch of commercially available composted organic green waste.  Both sites are composed largely of nonnative annual grasses.  The field experiment continued for three growing seasons. All plots were grazed using a rotational regime typical of the region during the spring and fall for up to four weeks, depending on the amount of available forage. 

Results  

  • Research indicated that a single application of composted green waste amendments significantly increased forage production (50%) and soil carbon sequestration (on average 1 ton/hectare) over three years.  Compost decomposition provides a slow release fertilizer to the soils leading to increase carbon sequestration and increased plant production.   
  • Net ecosystem carbon storage increased by 25–70% without including the direct addition of compost carbon (a total of 2.8 - 3.1 Mg C ha-1 over the first three years), while compost had no effect on nitrous oxide or methane emissions.  
  • The compost application doubled the production of grass for feed on the rangeland (Net Primary Production both above- and belowground increased by 2.1 +_ 0.8 Mg C/ha to 4.7 +_ 0.7 Mg C/ha (mean +_ SE))
  • The addition of compost led to increased water-holding capacity in soils.  

Implications

Sequestration of just 1 Mg C ha-1 y-1 (or one metric ton per hectare) on half the rangeland area in California would offset 42 million metric tons of CO2e, an amount equivalent to the annual GHG emissions from energy use for commercial and residential sectors in California.