REFERENCE SUFFICIENCY RANGES
FIELD CROPS

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Corn

C. R. Campbell and C. O. Plank

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• Critical Values
  
  
  • Tasseling
    
    

    Macronutrients
    N	P	K	Ca	Mg	S
    3.0%	0.25%	2.0%	0.4%	0.25%	0.12%

    
    

    Micronutrients
    Fe	Mn	Zn	Cu	B	Mo
    15 ppm	15 ppm	15 ppm	5 ppm	10 ppm	0.1 ppm

• Sampling Procedures

  Seedling (< 4 inches in height)
  Whole plants should be collected by cutting 1 inch above the soil surface. Depending on size, 15 to 20 plants are adequate for a sample.

  Early Growth (> 4 inches in height to tasseling)
  The most recent mature leaf (MRML) is the best indicator sample. Depending on size, 15 to 20 leaves are adequate for a sample.

  Tasseling / Bloom
  The earleaf is the best indicator sample. This is the leaf adjacent to the uppermost developing ear. Fifteen to twenty leaves are adequate for a sample.

  Maturity
  The earleaf is the best indicator sample. This is the leaf adjacent to the uppermost developing ear. Fifteen to twenty leaves are adequate for a sample.

  Notes for All Samples
  Problem-solving samples can be taken at any time during the growing season. Comparative samples of "good" and "bad" plants or sample areas should be taken according to guidelines at the stage of growth. Monitoring samples should be taken at lay-by and tasseling (bloom). Samples should be shipped to the laboratory in paper containers.

• Sufficiency Ranges
  
  

  Important Ratios

  The N:S ratio should be between 10 and 15 at all growth stages for optimum yields. Sulfur is limiting at N:S ratios greater than or equal to 18.

  • Seedling (< 4 inches in height)
    
    

    Macronutrients
    N	P	K	Ca	Mg	S
    4.0–5.0%	0.4–0.6%	3.0–4.0%	0.3–0.8%	0.2–0.6%	0.18–0.5%

    
    

    Micronutrients
    Fe	Mn	Zn	Cu	B	Mo
    40–250 ppm	25–160 ppm	20–60 ppm	6–20 ppm	5–25 ppm	0.1–2.0 ppm

  • Early Growth (> 4 inches in height to tasseling)
    
    

    Macronutrients
    N	P	K	Ca	Mg	S
    3.0–4.0%	0.3–0.5%	2.0–3.0%	0.25–0.8%	0.15–0.6%	0.15–0.4%

    
    

    Micronutrients
    Fe	Mn	Zn	Cu	B	Mo
    30–250 ppm	20–150 ppm	20–70 ppm	5–25 ppm	5–25 ppm	0.1–2.0 ppm

  • Tasseling / Bloom
    
    

    Macronutrients
    N	P	K	Ca	Mg	S
    2.8–4.0%	0.25–0.5%	1.8–3.0%	0.25–0.8%	0.15–0.6%	0.15–0.6%

    
    

    Micronutrients
    Fe	Mn	Zn	Cu	B	Mo
    30–250 ppm	15–150 ppm	20–70 ppm	5–25 ppm	5–25 ppm	0.1–2.0 ppm

  • Maturity
    
    

    Macronutrients
    N	P	K	Ca	Mg	S
    2.5–3.5%	0.25–0.4%	1.6–2.5%	0.2–0.8%	0.12–0.5%	0.12–0.4%

    
    

    Micronutrients
    Fe	Mn	Zn	Cu	B	Mo
    30–250 ppm	15–150 ppm	16–50 ppm	4–20 ppm	3–20 ppm	0.1–2.0 ppm

• DRIS Norms
  
  DRIS norms, based on a high-yielding subpopulation, have been provided by Elwali and others (1985).
  
  

  Parameter	No.	Mean	SD	Parameter	No.	Mean	SD
  N/P ‡	1909	9.035	2.136	10 N/Zn	1526	11.797	4.459
  N/K	1908	1.463	0.426	Zn/10 P	1527	0.883	0.420
  P/K	1909	0.169	0.054	Zn/10 K	1526	0.140	0.068
  Ca/N	1553	0.160	0.057	10 Ca/Zn	1524	1.919	1.087
  Ca/P	1554	1.447	0.612	10 Mg/Zn	1527	0.830	0.504
  Ca/K	1553	0.237	0.122	10 S/Zn	760	0.952	0.365
  Mg/N	1556	0.071	0.029	Fe/Zn	1268	4.464	1.837
  Mg/P	1557	0.639	0.330	Mn/Zn	1520	1.716	1.175
  Mg/K	1556	0.104	0.063	Cu/10 N	1401	0.031	0.013
  Mg/Ca	1554	0.465	0.182	Cu/10 P	1402	0.277	0.140
  S/N	788	0.084	0.019	Cu/10 K	1401	0.045	0.022
  S/P	788	0.703	0.225	10 Ca/Cu	1402	6.022	3.511
  S/K	787	0.114	0.029	10 Mg/Cu	1402	2.768	1.935
  Ca/S	785	1.978	0.893	Cu/10 S	664	0.375	0.211
  S/Mg	788	1.195	0.395	Cu/Fe	1236	0.079	0.036
  Fe/10 N	1297	0.394	0.097	Cu/Mn	1395	0.260	0.174
  Fe/10 P	1298	3.588	1.177	Cu/Zn	1372	0.356	0.200
  Fe/10 K	1297	0.568	0.201	B/10 N	402	0.024	0.012
  10 Ca/Fe	1298	0.410	0.189	B/10 P	403	0.269	0.135
  10 Mg/Fe	1298	0.190	0.098	B/10 K	402	0.043	0.033
  Fe/10 S	687	4.868	1.419	B/10 Ca	403	0.153	0.076
  Mn/10 N	1459	0.151	0.087	B/10 Mg	403	0.335	0.152
  Mn/10 P	1550	1.416	1.063	10 S/B	112	3.185	1.039
  Mn/10 K	1549	0.218	0.140	B/Fe	389	0.068	0.036
  Mn/10 Ca	1547	1.048	0.676	B/Mn	399	0.173	0.150
  Mn/10 Mg	1550	2.485	1.780	B/Zn	410	0.265	0.134
  10 S/Mn	782	0.648	0.351	B/Cu	401	0.950	0.620
  Mn/Fe	1293	0.405	0.249
  ‡ Nutrient concentrations are expressed in g/kg for N, P, K, Ca, Mg, and S and in mg/kg for Fe, Mn, Zn, Cu, and B. The data presented are number of observations (No.), means, and standard deviations (SD) of DRIS reference parameters in the subpopulation yielding > 10.0 Mg of grain per hectare.

• Remarks

  Sufficiency ranges are based on available literature and experience interpreting plant samples.

  DRIS should be used to support sufficiency range interpretation and identify the most limiting element or order of impact on growth.

  Results are less reliable as corn approaches maturity. Comparative "good" and "bad" samples should be used when sampling during various stages of maturity.

• References

  Elwali AMO, Gascho GJ, Sumner ME. 1985. DRIS norms for 11 nutrients in corn leaves. Agron J 77:506–8.

  Jones JB Jr, Eck HV, Voss R. 1990. Plant analysis as an aid in fertilizing corn and grain sorghum. In: Westerman RL, editor. Soil testing and plant analysis. 3rd ed. Madison (WI): Soil Society of America, Inc. p 521–47. (SSSA book series; 3).

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

  Plank CO. 1989. Plant analysis handbook for Georgia. Athens (GA): University of Georgia Cooperative Extension Service. p 21–8.

Electronic Document Prepared by:
Catherine Stokes, Communication Specialist
Agronomic Division of the N.C. Department of Agriculture and Consumer Services. July 2000.