The soil reaction (pH KCl) can be acidic (pH KCl < 7), neutral (pH KCl ~ 7) or alkaline (pH KCl > 7).
Each crop has different soil reaction requirements. Preferred pH KCl
7,0 - 7,57 beet, cabbage, alfalfa;
6,0 - 7,00 wheat, barley, maize, rape, peas, beans, clover, chard, cucumbers, onions;
5,5 - 6,00 rye, oats, grasses, radishes, carrots, tomatoes;
5,0 - 6,0 potatoes, flax;
4,2 - 5,2 individual crops (blueberries, cranberries).
In acid soils, most crops develop inefficient root systems, the overall biological activity of the soil decreases and some nutrients become difficult for plants to use.
Soil acidity is reduced by liming. The optimum liming rate should take into account the soil's granulometric composition, organic matter content and pH KCl. Even after liming, soils become progressively more acidic, so liming must be repeated.