REFERENCE SUFFICIENCY RANGES
FIELD CROPS

Tobacco, Flue-cured

C. R. Campbell

• Critical Values
  
  

  Limited published information:
  Boron (B)	15–16 ppm (bud leaves)
  Manganese (Mn)	18–25 ppm (most recent mature leaves)
  Magnesium (Mg)	0.2% (most recent mature leaves)

• Sampling Procedures

  The most recent mature or fully expanded leaf (MRML) is the best indicator of nutritional status. This is the first leaf back from the growing point that is fully developed. Cell division is complete, but cell expansion continues until maturity. The MRML is generally the 4th or 5th leaf back from the bud.

  To evaluate nitrogen status and gain information on ripeness for harvest, samples should be taken from the upper, middle or lower stalk positions.

  Depending on size, a total of 6 to 10 leaves are required for analysis. Laboratory work can be completed on only one leaf, but it must be representative of the area sampled. As leaves become larger, lamina from one side of the midrib can be removed from several leaves for a representative sample. Midribs should always be removed before grinding.

  Diagnostic samples should be taken at first signs of a problem. Comparative samples from "good" and "bad" plants should be taken along with soil from the root zones.

  To monitor nutritional status and fine tune fertilizer programs, samples should be taken at lay-by and topping. As the plant approaches maturity, samples of lower, middle, and upper stalk positions can be taken to further evaluate nitrogen status and assess ripeness for harvest.

  Samples are shipped to the laboratory in paper containers.

• Sufficiency Ranges
  
  
  • Most Recent Mature Leaf
    . . . Seedling
    . . . Early growth
    . . . Flowering
    . . . Maturity
  
  
  • Harvested Leaf
    . . . Upper
    . . . Middle
    . . . Lower
    
    

    Macronutrients
    Growth Stage	Tissue	N (%)	P (%)	K (%)	Ca (%)	Mg (%)	S (%)
    Seedling	MRML	4.0–6.0	0.2–0.5	3.0–4.0	0.6–1.5	0.2–0.6	0.15–0.6
    Early growth	MRML	4.0–5.0	0.2–0.5	2.5–3.5	0.75–1.5	0.2–0.6	0.15–0.6
    Flowering	MRML	3.5–4.5	0.2–0.5	2.5–3.5	0.75–1.5	0.2–0.6	0.15–0.6
    Maturity	MRML	2.25–3.0	0.17–0.5	1.6–3.0	0.75–1.5	0.2–0.6	0.15–0.6
    Harvest	Upper leaf	2.0–2.25	0.14–0.3	1.5–2.5	0.75–1.5	0.2–0.6	0.15–0.4
    Harvest	Middle leaf	1.6–2.0	0.13–0.3	1.5–2.5	1.0–2.0	0.2–0.6	0.15–0.4
    Harvest	Lower leaf	1.3–1.75	0.12–0.3	1.3–2.5	1.0–2.5	0.18–0.75	0.15–0.4

    
    

    Micronutrients
    Growth Stage	Tissue	Fe (ppm)	Mn (ppm)	Zn (ppm)	Cu (ppm)	B (ppm)
    Seedling	MRML	50–300	20–250	20–60	5–10	18–75
    Early growth	MRML	50–300	20–250	20–60	5–10	18–75
    Flowering	MRML	50–300	20–250	20–60	5–10	18–75
    Maturity	MRML	50–300	20–250	20–60	5–10	18–75
    Harvest	Upper leaf	40–200	20–350	18–60	5–10	18–30
    Harvest	Middle leaf	40–200	20–350	18–60	4–10	18–30
    Harvest	Lower leaf	40–200	18–350	18–60	3–10	15–30

    
    

    Excessive or Toxic Nutrient Levels

    Manganese toxicity can occur as concentration approaches 1000 ppm and is usually associated with low pH.

    
    

    Important Ratios

    The N:S ratio should be less than 18 at all growth stages.

• DRIS Norms

  DRIS norms have not been reported for flue-cured tobacco.

• Remarks

  Sufficiency ranges were established based on available references, research, crop monitoring, and experience interpreting analytical results.

• References

  Mills HA, Jones JB Jr. 1996. Plant analysis handbook II: a practical sampling, preparation, analysis, and interpretation guide. Athens (GA): Micro-Macro Publishing.

  Miner GS, Tucker MR. 1990. Plant analysis as an aid in fertilizing tobacco. In: Westerman RL, editor. Soil testing and plant analysis. 3rd ed. Madison (WI): Soil Science Society of America, Inc [SSSA]. p 645–57. (SSSA book series; 3).