REFERENCE SUFFICIENCY RANGES
VEGETABLE CROPS

Vidalia Onion

C. O. Plank

• Critical Values

  None established.

• Sampling Procedures

  Sample the most recently mature leaves prior to root or bulb enlargement. Avoid dusty or soil-covered leaves and plants whenever possible. Under normal conditions, rainfall is frequent enough to keep leaf surfaces fairly free of dust and soil particles. However, when leaves are dusty, brush or wipe with a damp cloth to remove the contaminants. If this is not effective or if leaves are covered with spray materials, wash in a mild detergent solution (0.30%) and rinse in running water. Do not prolong the washing procedures.

• Sufficiency Ranges
  
  

  Macronutrients
  N	P	K	Ca	Mg	S
  3.10–4.27%	0.26–0.48%	1.98–4.22%	0.90–1.84%	0.16–0.32%	0.15–0.57%

  
  

  Micronutrients
  Fe	Mn	Zn	Cu	B
  undetermined	51–149 ppm	16–45 ppm	5–28 ppm	6–15 ppm

  
  

  Important Ratios

  Maintain the N:S ratio between 5:1 and 15:1.

• DRIS Norms
  
  DRIS foliar norms for onions from populations yielding > 45 megagrams (metric tons) per hectare (n=173) (Caldwell 1991).
  
  

  Expression	Mean §	CV (%)	Expression	Mean §	CV (%)
  N	3.68	16	Mg/K	0.09	69
  P	0.37	29	S/K	0.12	47
  K	3.10	36	Mn/K	35.75	60
  S	0.36	57	Zn/K	10.60	50
  Ca	1.37	34	Cu/K	6.62	114
  Mg	0.24	33	B/K	3.78	53
  Mn	100.14	49	Mg/Ca	0.196	42
  Zn	30.21	48	S/Ca	0.31	85
  Cu	16.74	70	Mn/Ca	76.86	48
  B	10.62	43	Zn/Ca	25.00	70
  P/N	1.10	39	Cu/Ca	12.53	62
  K/N	0.85	39	B/Ca	8.93	67
  Ca/N	0.39	37	S/Mg	1.74	78
  Mg/N	0.07	41	Mn/Mg	492.91	79
  S/N	0.10	54	Zn/Mg	151.28	72
  Mn/N	28.66	53	Cu/Mg	77.18	72
  Zn/N	7.82	45	B/Mg	49.56	58
  Cu/N	4.83	73	Mn/S	331.70	55
  B/N	2.83	40	Zn/S	95.95	52
  K/P	9.34	50	Cu/S	59.33	89
  Ca/P	4.23	53	B/S	32.00	42
  Mg/P	0.69	40	Zn/Mn	0.34	52
  S/P	1.03	50	Cu/Mn	0.18	63
  Mn/P	312.28	70	B/Mn	0.12	51
  Zn/P	88.00	52	Cu/Zn	0.66	83
  Cu/P	51.05	86	B/Zn	0.38	41
  B/K	30.12	40	B/Cu	0.84	67
  Ca/K	0.54	78
  § Concentrations of N, P, K, Ca and Mg are expressed in dekagrams per kilogram and those of Zn, Cu and B in milligrams per kilogram.

• Remarks

  The sufficiency ranges were developed from the data of Caldwell (1991) by taking the mean plus or minus one standard deviation. Onion yields were in excess of 20 tons per acre. The ranges for N, P, K, Ca and Mg agree very closely with those reported by Pankov (1984) and, with but few exceptions, are not too dissimilar from those reported by Plank (1989) and Hochmuth and others (1991). These ranges have been checked against numerous normal- and abnormal-appearing farmer samples that were analyzed at the University of Georgia Soil Testing and Plant Analysis Laboratory and are improvements over previously used ranges (Plank 1989).

• References

  Caldwell, JO. 1991. Foliar and soil diagnosis and recommendation integrated system (DRIS) norms for onions (Allium cepa L.) and the effects of N and S on yield and pungency [MSc thesis]. Athens (GA): University of Georgia.

  Hochmuth GJ, Maynard D, Vavrina C, Hanlon EA. 1991. Plant tissue analysis and interpretations for vegetable crops in Florida. Gainesville (FL): University of Florida Cooperative Extension Service. Publication SS-VEC-42.

  Pankov, VV. 1984. Leaf analysis in relation to onion nutrition. In: Proceedings 6th international colloquium for the optimization of plant nutrition. Volume 2. Montpellier (France): AIONP/GERDAT. p 449–56.

  Plank CO. 1989. Plant analysis handbook for Georgia. Athens (GA): University of Georgia Cooperative Extension Service. 64 p.

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