Lucerne is a perennial crop with high demands in terms of soil fertility. Soil analyses will be essential to determine the soil fertility and to set up a fertilizer plan. The main recommendations for fertilizing lucerne are given in the table below.
General fertilizer guidelines for lucerne
There are general recommendations. Exact fertilization should be based on a soil analysis.
| Sandy soil | Clay soil | Period | Fertilizer type | |
| Lime (CaCO3) |
Aim for pH = 6,0 |
Aim for pH = 6,5 |
Before sowing | Artificial |
| Nitrogen(N) | 25 | 25 | Before/at sowing | Artificial |
|
Phosphorus (P2O5) |
80-110 | 80-110 |
Before growing season |
Animal / Artificial |
|
Potassium (K2O) |
180-220 | 150-190 |
1-3 times during growth season* |
Animal / Artificial |
| Magnesium (MgO) | 50 | 0 |
Before growing season |
Artificial |
* On soils which are sensitive to leaching, potassium (K) should be applied several times during the season. On soils with a high binding capacity, K-supplementation can be supplied at once per year.
Another essential mineral in growing lucerne is Sulphur (S). This nutrient is important for protein formation within plants and thus, influence the crude protein content of lucerne silage or hay. Soils low in sulphur should be given additional fertilizer.
Two essential micro-elements are Molybdenum (Mb) and Boron (B). For Rhizobia growth Molybdenum is needed. Boron prevents drought stress in lucerne. Both elements are likely to be limiting on poor sandy soils.
There’s an enormous effect of P and K supply on lucerne yield. This is shown in trial results from the Purdue University in USA (see picture):
Manure or slurry are preferable applied before sowing. Up to 30 tons per hectare can be applied before ploughing/cultivation. High gifts aren’t recommended though, as available nitrogen inhibits Rhizobium activity.
If used in an existing stand, manure or slurry should be applied at the beginning of the growth season before the first lucerne sprouts emerge. Handling slurry or manure is a potential risk to stand persistency, as lucerne plants are easily damaged by heavy machines.
Some shortages in nutrients can be clearly identified in lucerne stands, as described below. Generally, nutrient deficiencies come back to poor inoculation, too less P/K-fertilizer or low soil quality.
Nitrogen deficiency – yellowish/light-green colored plants, stunted growth. This indicates a lack of active Rhizobium in the soil, which might come from using untreated seeds, a low soil-pH or Molybdenum-deficiency.
Phosphorus deficiency – stunted growth, plants are stiff and upright. Leaves tend to curl and purple coloration. Occurs mostly in spring, when soil temperature is low.
Potassium deficiency – small white spots on the older leaves, on leaf margins. Later turning yellow. Occurs more often after the 1st cut and K-deficient stands can show more winterdamaga.
Magnesium deficiency – younger leaves start yellowing, margins initially stay green. Might be identified as K-deficiency too.
Depending on the climate zones, Barenbrug offers various Lucerne products. Every product has its own features suitable for different conditions.
