@ janani, as Dr. Singh point out , for conversion soil bulk density value is required (in kg/m3) and the depth of the soil layer (in meters). As a thumb rule you may divide by 2 for the conversion from kg/ha to ppm.. In your case the result may come approximately 17.5 ppm.
Dear Janani
I will provide you with detailed method of calculation which you can use at all times.
We need bulk density and soil depth to calculate the mass of 1 ha soil to estimate the concentration of P in ppm.
Assumptions: Bulk density = d tonne/m3, soil depth = 0.15 m
Mass of 1 ha soil at 0.15 m depth = bulk density x volume = d x 10,000 m2 x 0.15 m, which is 1500 d tonnes.
Now, we need to convert 34 kg-P/ha soil to gram P/ha of soil which is 34x1000 g P/ha soil (this is because 1 ppm = one in one million, therefore 1 g P divided by 1 tonne soil will be 1 ppm)
The concentration of P in ppm = 34000 g P ÷ 1500d tonne soil
If I assume the bulk density is 1.2 tonne/m3 (which is similar to 1.2 g/cubic centimetre or 1.2 kg/L), the answer is 34000 g P ÷ 1500 x 1.2 = 18.89 ppm (which means there is 18.89 g of P in every tonne of soil or 18.89 mg of P in every kg of soil).
Greater the bulk density, lower the concentration of P.
Kind regards
Selva
If the bulk density is 1.2 g/cm3 and the soil depth is 15 cm the answer is as I provided in my example, which is 18.89 ppm.
You need few more data such as depth of soil and bulk density.
Again assuming 15 cm soil depth and 1.2 g/cm3 bulk density, the volume of the soil in 1 ha = 0.15 m x 10,000 m2 = 1500 m3
When convert the above soil volume to mass = volume x soil density
1500 m3 x 1.2 t/m3 = 1800 t of soil layer in a ha (1,800,000 kg).
To estimate 0.023% of N, you need to multiply by the above % with soil mass and divide by 100:
which is, 1,800,000 x 0.023/100 = 414 kg N/ha
The simplest way to convert ppm values into kg/ha are as follow,
1st. Calculate the mass of 1 ha of soil (kg/ha).
· Mass of soil (kg/ha) = Soil bulk density (kg/m3) * Soil depth (m)*104 m2/ha.
2nd. Then, multiply the ppm value by the mass of 1 ha of soil.
If, for example:
- The analytical result is 5 mg/kg P = 5 ppm.
- Bulk density 1.5 g/cm3 = 1.5 x 103 kg/m3
- Soil depth is 25 cm = 0.25m
* Then, convert 5 ppm P to kg/ha P.
- First , soil mass/ha = bulk density *depth* area =1.5 x 103 kg/m3 *0.25m *104 m2/ha = 3.75x106 kg/ha.
o Then, multiply the ppm value by the mass of 1ha of soil: 3.75x106 kg/ha *5ppm/10-6 = 18.75 kg P/ha
Converting ppm to kg/ha
soil depth 0.15 m (15 cm or 6 inches), then Value in kg/ha = Value in ppm x 1.5
Rationale: Value in kg/ha = Value in ppm x (1 kg/106 mg) x (1000 kg/m3, bulk density) x (0.15 m x 104 m2/ha)
We know that weight of 1 hectare soil (usually upto 15 cm soil depth so called furrow slice) is 2.24 × 1000000 kg...In one hectare, 35 kg available phosphorus is present, it means
2.24× 1000000 kg soil contain= 35 kg P
Then 1 kg soil will contain= 35/2.24×1000000 kg P
(To convert in parts per million, it means 1kg/1000000kg)
Then 1000000 kg soil will contain= 35×1000000/2.24×1000000= 35/2.24= 15.56 ppm Phosphorus...
It can be understood by using formula as kg/ha= 2.24 × ppm
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