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Agronomic Services

Crop Fertilization Based on North Carolina Soil Tests
Table 1.4  Multiplication factors for converting soil test index values to a quantitative equivalent*
Soil Test Index Value mg/dm³ kg/ha lb/acre meq/100 cm³ meq/dm³
P-I 1.2 2.40 2.138 N/A N/A
K-I 1.955 3.91 3.484 0.005 0.05
Ca% × CEC 200.0 400.0 356.40 1.0 10.0
Mg% × CEC 121.6 243.2 216.69 1.0 10.0
Na 230.0 460.0 409.86 1.0 10.0
Mn-I 0.16 0.32 0.285 N/A N/A
Zn-I 0.04 0.08 0.071 N/A N/A
Cu-I 0.02 0.04 0.036 N/A N/A
S-I 0.48 0.96 0.857 N/A N/A
* Soil tests in North Carolina are made on a volume of soil. Conversion to an area equivalent is based on a depth of 20 cm (7.9 inches). To convert phosphorus and potassium from the elemental forms to lb/acre, use these multipliers: 2.29 × P gives lb of P2O5 per acre; and 1.2 × K gives lb of K2O per acre.

The Volume Rationale: The area of a hectare (ha) is 10,000 or 1,000,000 dm². The volume per hectare to a depth of 20 cm or 2 dm equals 2,000,000 dm³. The following conversion factors apply: mg/dm³ = parts per million (ppm); mg/dm³ × 2 = kg/ha; kg/ha × 0.893 = lb/acre; or mg/dm³ × 1.78 = lb/acre. Refer to Part IV of this manual for other conversion factors.

return icon.Hardy DH, Tucker MR, Stokes CE. 2014. Crop fertilization based on North Carolina soil tests. Raleigh (NC): North Carolina Department of Agriculture and Consumer Services, Agronomic Division. Circular No. 1.

Last Update January 10, 2014

 

NCDA&CS Agronomic Services Division, Colleen M. Hudak-Wise, Ph.D., Director
Mailing Address: 1040 Mail Service Center, Raleigh NC 27699-1040
Physical Address: 4300 Reedy Creek Road, Raleigh NC 27607-6465
Phone: (919) 733-2655; FAX: (919) 733-2837



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