Patentkali fertiliser granules, potash, magnesia and sulphur

You buy this fertiliser for its potash, and at the same time you supply a great deal of sulphur, whose content expressed as SO3 even exceeds that of the potash. The potassium and magnesium are indeed present as sulphates, and sulphur goes into the making of the plant's proteins. Magnesium sits at the centre of the chlorophyll molecule, which is why a deficiency shows first in the colour of the leaves, while potassium regulates the opening of the stomata and the transport of sugars to the fruit. These three elements complement one another, which sets this granule apart from a simple potash supply.

The reference rates relate to field-scale growing and to soils of average fertility, but they convert easily to garden scale, since 100 kg per hectare is equivalent to 10 g per square metre. The 550 to 650 kg for a potato crop thus becomes 55 to 65 g per square metre, or 550 to 650 g for a 10 m² bed, and the 200 to 400 kg for fruit trees gives 20 to 40 g per square metre of orchard. A 1 kg bag therefore covers a potato bed of 15 to 18 m².

In your vegetable garden, observation then refines these guidelines. Leaf edges that dry out, fragile stems or yellowing between the veins of older leaves signal that an element is lacking, and the article on plant deficiencies in aquaponics helps you tell them apart. Scatter the granules by hand, then rake lightly to bring them into contact with the moist soil. As potassium and magnesium are already soluble, watering or rain is enough to make them available to the roots.