Fertilization of legumes

Legumes primarily include clover, alfalfa, birdsfoot, beans, peas, lentils, soybeans and licorice. These are plants whose cultivation has a significant positive impact on the fertility of our soils, enriching them with nitrogen and contributing to their loosening. However, the cultivation of legumes requires proper care and the provision of sufficient nutrients.
All farmers know how important legumes are in crop rotation: grown for green manure, they improve the soil’s lumpy structure, its water and thermal conditions, enrich it with nitrogen (50 to 250 kg/ha) and significant amounts of phosphorus, calcium, sulfur, potassium and magnesium. When grown for fodder (in the form of browse, hay, silage or seeds), they provide animals with large amounts of protein, vitamins and mineral salts. In the fertilization of legumes, it is necessary to take into account all the mineral nutrients necessary for the plants. In specific soil conditions, it is therefore necessary to use multicomponent mineral fertilizers.

Due to the special property of legumes, which is symbiosis with papillary bacteria that bond with atmospheric nitrogen from the soil air, these plants are generally not fertilized with nitrogen. In the presence of nitrates and ammonium salts, the formation of papillae on the roots is hindered or completely ceases. Another reason for the non-formation of papillae can be too acidic soil reaction. In both cases, nitrogen fertilization cannot replace the specific nature of symbiosis – yields and nitrogen content of biomass decrease. Visible symptoms of nitrogen starvation include yellowing and then purpling of leaves, soaring plant shape and poor flowering and fruiting.

An optimal supply of phosphorus to legumes promotes nitrogen fixation by papillary bacteria and facilitates the conversion of mineral nitrogen into protein. Failure to fertilize with readily available phosphorus fertilizers always results in a rapid and significant reduction in yields, regardless of soil richness. External symptoms of phosphorus deficiency include weakened growth, soaring plant shape, purple and brown coloration of the oldest leaves and delayed ripening. On soils that are particularly low in phosphorus, legumes should be fertilized with fertilizers with a high concentration of phosphorus, such as granular simple Superphosphate.

For good yields of legumes, especially clover and alfalfa, potassium fertilization is essential. Symptoms of potassium deficiency are flaccidity of plants, their small size, drying of leaves. Characteristic are very small and numerous necrotic spots between the innervation of the leaves.

Legumes require a large amount of calcium in the soil (the soil is not limed only under yellow lupine and birdsfoot). Symptoms of a lack of calcium in plants include bending and then breaking the tops of the stems and dying of inflorescences. All fertilizers produced by Fosfan contain sufficient amounts of calcium for legumes. Only on very acidic soils is liming necessary.

The presence of magnesium in the soil makes it easier for plants to take up phosphorus. Legumes take up amounts of magnesium much more than other crops. All legumes respond to magnesium deficiency in the soil. Characteristic symptoms of deficiency are yellow-green coloration of leaves with darker bands of green along the innervation (known as marbling).

Legumes require particularly high amounts of sulfur in the soil. On sulfur-poor soils, the introduction of the element in question clearly improves the yield of these plants. Often the symptoms of a lack of sulfur are confused with those of a lack of nitrogen, because in both cases the plants are fine and chlorotic.