REFERENCE SUFFICIENCY RANGES
FORAGES AND HAY CROPS

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Alfalfa

C. O. Plank

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• Critical Values

  None established.

• Sampling Procedures

  Sample the top 4 to 6 inches of the plant prior to or at 1/10 bloom stage.

• Sufficiency Ranges
  
  

  Macronutrients
  N	P	K	Ca	Mg	S
  3.00–5.00%	0.25–0.70%	2.00–3.50%	0.80–3.00%	0.25–1.00%	0.25–0.50%

  
  

  Micronutrients
  Fe	Mn	Zn	Cu	B
  30–250 ppm	25–100 ppm	20–70 ppm	4–30 ppm	20–80 ppm

  
  

  Important Ratios

  Maintain the N:S ratio between 10:1 and 15:1 for ruminant nutrition.

• DRIS Norms
  
  DRIS norms from populations yielding 3.5 megagrams (metric tons) per hectare per cutting are given below (Walworth and others 1986). These norms were developed from alfalfa grown in Georgia using the harvested aerial portion of the plants at approximately 1/10th bloom.
  
  

  Expression	Norms §	CV (%)	Expression	Norms §	CV (%)
  (N/DM) × 100	2.952	7.2	(Ca/DM) × 100	1.186	13.1
  N/P	12.450	19.1	Mg/Ca	0.1365	23.1
  N/K	1.499	18.2	Zn/Ca	18.27	24.7
  N/Ca	2.534	11.6	Cu/Ca	7.097	19.3
  Mg/N	0.0550	22.6	B/Ca	34.06	20.7
  N/Zn	0.1504	24.5	(Mg/DM) × 100	0.1609	19.2
  N/Cu	0.4583	26.1	Zn/Mg	132.60	31.5
  B/N	15.09	19.6	Cu/Mg	43.96	28.0
  (P/DM) × 100	0.2435	15.5	B/Mg	279.50	23.7
  P/K	0.1240	23.8	(Zn/DM) × 106	21.44	49.8
  P/Ca	0.2163	23.8	Cu/Zn	0.3462	29.0
  Mg/P	0.6722	21.3	Zn/B	0.4967	47.4
  Zn/P	90.45	55.6	(Cu/DM) × 106	6.886	26.6
  Cu/P	28.68	27.8	B/Cu	7.048	37.7
  B/P	185.40	26.2	(B/DM) × 106	44.18	17.9
  (K/DM) × 100	2.034	19.1
  K/Ca	1.938	19.3
  Mg/K	0.0831	31.9
  K/Zn	0.1026	27.0
  Cu/K	3.431	15.5
  B/K	23.13	33.7
  § 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

  DRIS norms developed for some crops may vary somewhat from one geographical region to another. This is illustrated by the work of Walworth and others (1986) who showed that norms developed for alfalfa in the Midwest (Erickson and others 1982) differed significantly from those developed in Georgia. Soils in the two regions differ appreciably and are believed to account for the wide differences in Mg and B norms between the regions. Consequently, when such factors are known, they should be taken into account when selecting both DRIS norms and sufficiency ranges for interpretative purposes.

• References

  Erickson T, Kelling KA, Shulte EE. 1982. Predicting alfalfa nutrient needs through DRIS. Proc 1982 Wisconsin Fert Agric Lime Pest Mgmt Conf 21:233–46.

  Kresge CB, Younts SE. 1962. Effect of various rates and frequencies of potassium application on yield and chemical composition of alfalfa and alfalfa-orchardgrass. Agron J 54:313–6.

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

  Walworth JL, Sumner ME, Isaac RA, Plank CO. 1986. Preliminary DRIS norms for alfalfa in the southeastern United States and a comparison with midwestern norms. Agron J 78:1046–52.

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