|
A literature review of soil carbon under pasture, horticulture and arable land uses
Summary
Carbon (C) is an essential constituent of biological life on earth. Most C on earth is not in living organisms but is present in vast amounts in rocks such as limestone, and in dead organic matter. For terrestrial ecosystems, there is more C in soil organic matter (SOM), than in the living plants and animals, and the atmosphere. It has been estimated that soil contains 1,200-1,550 Pg C to a depth of 1 m, and 2,370-2,450 Pg C to a depth of 2 m.
Comparative estimates of organic C contained in living biomass (560 Pg) and atmospheric CO2-C (760 Pg) indicates that a small shift in the soil organic C pool has the potential to have a significant impact on atmospheric C concentrations.
Organic matter helps soils to retain and store water and plant nutrients, to resist erosion, form stable aggregates, improve water infiltration and drainage, and provide a food source and habitat for soil dwelling organisms. The C in organic matter is from a complex mix of different compounds that is undergoing constant change as fresh organic matter is added, and organic matter decomposes. Once lost from the soil organic C pool, replenishment can take many years, even centuries.
For New Zealand soils the total C content, measured by high temperature combustion, provides a reliable measure of the organic C content. Important considerations for estimating C stocks in a soil are a representative sample, the depth of sampling and bulk densities.
This literature review summarizes the impacts of different land uses namely pasture, arable and horticulture on soil C levels. It also covers options for increasing C sequestration in soils through adaptation of soil and crop management and organic inputs, soil C as a soil quality indicator and emerging approaches for valuing soil C.
|
