Type of property

Standard

Institute of standards and industrial research of Iran (weight based on the dry matter)

Standard products Washington ecology department

Acceptable range for Category A

Acceptable range for Category B

WHO standard (gr/100gr)

Gotas theory (gr/100gr)

Category A*

Category B*

Organic materials

At least 35%

At least 25%

10 - 20

25 - 50

At least 50

At least 40

Organic carbon

At least 25%

At least 15%

-

50 - 80

-

-

The amount of total nitrogen

1.25% - 1.66%

1% - 1.5%

0.4% - 3.5%

0.4% - 1.5%

At least 1%

At least 0.5%

The ratio of carbon to nitrogen

15 - 20

10 - 15

-

-

Up to 15

Up to 20

The amount of phosphorus in terms of P2O5

1% - 3.8%

0.3% - 3.8%

0.3 - 3.5

0.2 - 3.8

-

-

The amount of potassium in terms of K2O

0.5% - 1.8%

0.5% - 1.8%

0.5 - 1.8

0.1 - 2.8

-

-

Sodium

-

-

-

-

-

-

Arsenic (mg/kg)

-

-

-

-

-

-

Lead (mg/kg)

-

-

200 - 400

-

-

-

Cadmium (mg/kg)

-

-

15 - 40

-

-

-

Mercury (mg/kg)

-

-

-

-

-

-

Chromium (mg/kg)

-

-

-

-

-

-

Conductivity (in 10% of dry matter)

Up to 8 ds/m

Up to 14 ds/m

-

-

<2 mmohs/cm

<3 mmohs/cm

pH (in 10% of dry matter)

6 - 8

6 - 8

6 - 8

6 - 9

5.5 - 6.5

5 - 8