Every crop has an optimum soil pH range. Within this range, production potential is maximised. The plant’s critical range is the range of soil pH in which the crop will obtain 80% of maximum yield potential. If a crop is grown in a soil where the pH level is either too low (acidic) or too high (too alkaline), then productivity will decline to below 80% of maximum yield potential. Crops that have an optimum pH range that is less than 4.5 are described as acid tolerant (rye, oats, and lupins), while plants that have an optimum pH range above 6 are acid sensitive.