Alkaline (adj.): Soil with a reading above 7.0 on the pH scale. Alkaline soils have more lime than acidic soil, and lime is beneficial for growing many vegetable plants and desert plants in container gardens. Any potting soil that is too alkaline will affect plant growth. Soil pH can be measured with a pH test kit and fixed with aluminum sulfate, sphagnum peat moss, etc., if too alkaline. Alkaline potting soil is also called “sweet” soil.