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Crop Fertilization Based on North Carolina Soil Tests
Table 2.4  Equations for calculating rates of P2O5 and K2O *
Equation Reference No. Equation
1 0.0467 – 13.0 I + 900 = lb/acre
2 0.0202 – 6.37 I + 500 = lb/acre
3 0.0100 – 3.50 I + 300 = lb/acre
4 0.0175 – 4.46 I + 300 = lb/acre
5 0.0193 – 4.90 I + 300 = lb/acre
6 0.0272 – 6.08 I + 300 = lb/acre
7 0.0100 – 3.25 I + 250 = lb/acre
8 0.0173 – 4.64 I + 250 = lb/acre
9 0.0102 – 3.00 I + 220 = lb/acre
10 0.0103 – 2.90 I + 200 = lb/acre
11 0.0190 – 4.20 I + 200 = lb/acre
12 0.0053 – 2.00 I + 180 = lb/acre
13 0.0120 – 2.90 I + 165 = lb/acre
14 0.0116 – 2.75 I + 150 = lb/acre
15 0.0140 – 3.20 I + 150 = lb/acre
16 0.0227 – 4.42 I + 150 = lb/acre
17 0.0084 – 2.19 I + 140 = lb/acre
18 0.0120 – 3.00 I + 120 = lb/acre
19 0.0044 – 1.60 I + 100 = lb/acre
20 0.0120 – 2.40 I + 80 = lb/acre
21 0.0012 – 0.315 I + 20 = lb/1000 ft²
22 0.0005 – 0.418 I + 11 = lb/1000 ft²
23 0.0005 – 0.135 I + 9 = lb/1000 ft²
24 0.0007 – 0.160 I + 8 = lb/1000 ft²
25 0.0005 – 0.130 I + 6.5 = lb/1000 ft²
* Refer to Table 2.3 to match the appropriate equation with the desired crop. Insert the current soil test index value (I) into the equation and solve for the suggested fertilizer rates. The rate of fertilizer suggested ranges 10 lb above and below the calculated value. The results of the above equations for specific soil test indexes are shown in Table 2.5.
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