Administrative Rules of Montana
Department 4 - AGRICULTURE
Chapter 4.12 - AGRICULTURAL SCIENCES DIVISION
Subchapter 4.12.6 - Fertilizer Regulations
Rule 4.12.607 - INVESTIGATIONAL ALLOWANCES AND OVERALL INDEX VALUE

Universal Citation: MT Admin Rules 4.12.607

Current through Register Vol. 18, September 20, 2024

(1) A commercial fertilizer shall be deemed deficient if the analysis of nutrient is below the guarantee by an amount exceeding the values in the following schedule, or if the overall index value of the fertilizer is below 98%.

Guarantee Percent

Nitrogen (N)

Available Phosphate (P2O5)

Soluble Potash (K2O)

Investigational Allowance, percent

4 or less

0.49

0.67

0.41

5

0.51

0.67

0.43

6

0.52

0.67

0.47

7

0.54

0.68

0.53

8

0.55

0.68

0.60

9

0.57

0.68

0.65

10

0.58

0.69

0.70

12

0.61

0.69

0.79

14

0.63

0.70

0.87

16

0.67

0.70

0.94

18

0.70

0.71

1.01

20

0.73

0.72

1.08

22

0.75

0.72

1.15

24

0.78

0.73

1.21

26

0.81

0.73

1.27

28

0.83

0.74

1.33

30

0.86

0.75

1.39

32 or more

0.88

0.76

1.44
(a) For DAP and MAP the investigational allowance for available phosphate shall be 0.70.

(b) For TSP the investigational allowance shall be 1.53.

(c) For guarantees not listed, calculate the appropriate value by interpolation.

(d) The overall index value is calculated by comparing the commercial value guaranteed with the commercial value found.

Example of calculation for a 10-10-10 grade found to contain 10.1% Total Nitrogen (N), 9.4% Available Phosphate (P205), and 10.1% Soluble Potash (K20). Nutrient unit values are assumed to be $3 per unit N, $2 per unit P205, and $1 per unit K20.

10.0 units N x 3 = 30.0
10.0 units P205 x 2 = 20.0
10.0 units K20 x 1 = 10.0
Commercial Value Guaranteed 60.0

10.1 units N x 3 = 30.3
9.4 units P205 x 2 = 18.8
10.1 units K20 x 1 = 10.1
Commercial Value Found 59.2

Overall Index Value - (59.2/60.0) x 100 = 98.6%

(2) Secondary and micro plant nutrients shall be deemed deficient if the analysis of any element is below the guarantee by an amount exceeding the values calculated according to the following schedule:

Element Allowable Deficiency
Calcium 0.2 unit + 5% of guarantee
Magnesium 0.2 unit + 5% of guarantee
Sulfur 0.2 unit + 5% of guarantee
Boron 0.003 unit + 15% of guarantee
Cobalt 0.0001 unit + 30% of guarantee
Molybdenum 0.0001 unit + 30% of guarantee
Chlorine 0.005 unit + 10% of guarantee
Copper 0.005 unit + 10% of guarantee
Iron 0.005 unit + 10% of guarantee
Manganese 0.005 unit + 10% of guarantee
Sodium 0.005 unit + 10% of guarantee
Zinc 0.005 unit + 10% of guarantee

The maximum allowance when calculated in accordance to the above shall be one unit (one percentage point).

AUTH: 80-10-301, MCA; IMP: 80-10-206, MCA

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