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Below is an alfalfa (Medicago sativa L.) tissue nutrient sufficiency table by growth stage, including macronutrients (nitrogen, phosphorus, potassium, calcium, magnesium, sulfur), micronutrients (boron, copper, iron, manganese, zinc, molybdenum), leaf water content (LWC), and Brix values. These values are based on tissue analysis (typically the top 6 inches of the plant or the uppermost fully expanded leaves) and are derived from agricultural research, such as guidelines from the University of California, University of Wisconsin, and other alfalfa-growing regions, adjusted for alfalfa physiology.
Alfalfa is a perennial forage crop, and its growth stages are typically defined by cutting cycles:
- Early Vegetative (post-cutting regrowth to 6–12 inches)
- Late Vegetative (pre-bud, 12–18 inches)
- Bud to Early Flower (flowering initiation)
- Full Flower to Maturity (post-flowering, pre-cut)
- Harvest
Nutrient concentrations are in percentages (%) for macronutrients and parts per million (ppm) for micronutrients, with LWC as a percentage of fresh weight and Brix (°Bx) as soluble solids in sap.
|
Growth Stage |
N (%) |
P (%) |
K (%) |
Mg (%) |
Ca (%) |
S (%) |
||||||
|
Min |
Max |
Min |
Max |
Min |
Max |
Min |
Max |
Min |
Max |
Min |
Max |
|
|
Early Vegetative |
4.00 |
5.50 |
0.30 |
0.50 |
2.50 |
3.50 |
0.30 |
0.60 |
1.50 |
2.50 |
0.30 |
0.50 |
|
Late Vegetative |
4.00 |
5.00 |
0.30 |
0.50 |
2.00 |
3.00 |
0.30 |
0.60 |
1.50 |
2.50 |
0.30 |
0.50 |
|
Bud to Early Flower |
3.50 |
4.50 |
0.20 |
0.40 |
1.80 |
2.50 |
0.30 |
0.60 |
1.50 |
2.50 |
0.20 |
0.40 |
|
Full Flower |
3.00 |
4.00 |
0.20 |
0.40 |
1.50 |
2.20 |
0.30 |
0.60 |
1.50 |
2.50 |
0.20 |
0.40 |
|
Harvest |
2.00 |
3.00 |
0.15 |
0.30 |
1.00 |
2.00 |
0.20 |
0.40 |
1.00 |
2.00 |
0.20 |
0.40 |
|
B (ppm) |
Zn (ppm) |
Mn (ppm) |
Fe (ppm) |
Cu (ppm) |
Mo (ppm) |
|||||||
|
Min |
Max |
Min |
Max |
Min |
Max |
Min |
Max |
Min |
Max |
Min |
Max |
|
|
Early Vegetative |
30 |
50 |
20 |
60 |
30 |
100 |
50 |
200 |
5 |
15 |
0.50 |
2.00 |
|
Late Vegetative |
30 |
50 |
20 |
60 |
30 |
100 |
50 |
200 |
5 |
15 |
0.50 |
2.00 |
|
Bud to Early Flower |
30 |
50 |
20 |
60 |
30 |
100 |
50 |
200 |
5 |
15 |
0.50 |
2.00 |
|
Full Flower |
30 |
50 |
20 |
60 |
30 |
100 |
50 |
200 |
5 |
15 |
0.50 |
2.00 |
|
Harvest |
20 |
40 |
15 |
50 |
20 |
75 |
30 |
150 |
4 |
10 |
0.50 |
2.00 |
|
LWC |
BRIX |
|||||||||||
|
Min |
Max |
Min |
Max |
|||||||||
|
Early Vegetative |
85 |
90 |
8 |
12 |
||||||||
|
Late Vegetative |
80 |
88 |
10 |
15 |
||||||||
|
Bud to Early Flower |
78 |
85 |
12 |
18 |
||||||||
|
Full Flower |
75 |
82 |
8 |
14 |
||||||||
|
Harvest |
15 |
20 |
8 |
12 |
||||||||
Scanning Recommendation:
- Ensure that over 25% of the scan bed is covered with a single layer of vegetation.
- Leaf selection should be similar to this illustration.
