Hello Jonathan,

In order to convert between the two units, you would need to define the depth of the soil profile you are looking at and the bulk density of the soil. Since assessments between studies vary in depth and soil conditions that affect bulk density (e.g. texture, management), it’s practically impossible to reconcile the two units with a single conversion factor. Here is an illustration assuming a soil carbon assessment in the top 0.3 m of the soil profile. The total volume of soil of this layer in 1 ha = 0.3m x 10,000m^2/ha = 3,000 m^3/ha. Assuming an average soil bulk density for this soil layer (e.g. 1,400 kg/m^3), you have 3,000 m^3/ha x 1,400kg/m^3 = 4,200,000 kg/ha in the top 0.3m. Multiplying the carbon content in g/kg by this total, you arrive at the total carbon in g/ha, which you can convert to tonnes/ha (again, in the top 0.3 m). As these calculations suggest, the amount of carbon depends on the depth considered and is very sensitive to soil bulk density, which can vary quite a bit in the top 0.3 m of the soil.

Hope this helps.

Marcos

Hello Jonathan,

You can convert a g/kg percentage to kg/ha by the assumption that, soil bulk density has an average value which is generally more than 1 and less than 1.5 kg/liter and for a manuscript or thesis study of you, you can assume that value 1.4 kg/liter. So, if you would like to convert a kg/ha value to g/kg; you can just multiply a g/kg value with: 7,142857.

If I need to explain how you can reach that value;

Lets say that one manuscript is giving the value for carbon content in the soil as 3.2 g/kg.

You want to convert this to kg/ha.

3,2 / 1,4 = 2,285714 g /liter

1,4 is the value of soil bulk density that you can accept.

when you divide the result ( 2,285714 g /liter) into 1000; you convert gram to kg.

this result makes to jump to a soil carbon content value of a 1mm thick soil of 1 m2.

then if you multiply this value with 10000, this time you obtain the ha value.

thus; your factor is: ((A/1,4/1000)*10000)=7,142857.

where A maybe in this case 3,2 g/kg carbon content of a soil.

If you multiply 3,2 x 7,142857 = 22,85714 kg/ha for the 1 mm thickness of the soil.

If you would like to discuss the 1 m deep soil, you can multiply this value with 1000. (1 m = 1000 mm).

Correction:

Please apply the formula with that difference:

((A x 1,4 / 1000) x 10000)= 14

where A maybe in your case as in my previous response 3,2 g/kg carbon content of a soil.

Then continue as the same calculation:

If the gr/kg value is 3,2, you can multiply 3,2 x 14 = 44,8 kg / ha to obtain

kg/ha value.

1g/kg = 0.001kg/kg =.001 since 1000g = 1kg > 1g = 0.001kg

assuming a furrow slice of soil 0.3m depth and bulk density of 1400kg/m3,

mass of soil in 1ha (10,000m2) is 1400kg/m3 x 10,000m2 x 0.3m = 4,200,000kg

if 1g/kg (0.001kg /kg ie 0.001) to be converted to kg/ha > 0.001 x 4,200,000 = 4200 kg/ha since 4,200, 000 kg is contained in 1ha.

To convert 4200 kg/ha to tonnes /ha, divide by 1000 since 1 tonne= 1000kg > 4200/1000 = 4.2

Hence, to convert g/kg to tonne/ha, use a factor of 4.2 to multiply it based on a furrow slice depth of 0.3m (30cm) and a bulk density of 1400 kg/m3 (1.4g/cm3)

If you want to convert the soil carbon content, unit, from g/kg to tons/hectare then you must have the soil bulk density value of the particular soil type with depth. Kindly see this research paper for further details: Schlesinger W.H., 1990. Evidence from chronosequence studies for a low carbon storage potential of soils. Nature, 348, 232-234.

Thank you everyone for the replies. This is very helpful.

Bulk density of the soil with depth is needed

With the help of bulk density and soil depth

Following

In addition to what Marcos describes as the calculation, you need to get the bulk density. you can use this link:

https://data.isric.org/geonetwork/srv/eng/catalog.search#/metadata/2ebc3811-2783-4fb6-bb68-e8af47d32fd3