It means you need to be very aware that the natural tendency of soils irrigated with water treated with bases like calcium hydroxide to raise their pH level is to have their pH increase with time. This is especially so if you're unable to regularly flush the soil, because the base compounds tend to build up in the soil. For example. I don't usually see any signs of a pH induced Fe (iron) deficiency in the summer when plants are outdoors and I water with the hose, flushing them very thoroughly each time I water. In winter, those plants I over-winter indoors don't get as thorough a flushing as they do in summer, and I OFTEN see pH induced Fe deficiencies. To correct that issue, I'll add enough vinegar or citric acid to my irrigation water to bring the pH down to 5.0, which immediately fixes the Fe deficiency. This is why it's poor practice to reach for an Fe supplement as soon as you see chlorosis in your plant. Undoubtedly, a sufficient supply of Fe is already IN the soil - you just need to make it available by lowering pH.

Many of the micronutrients also precipitate from the soil solution at high pH. This means they form insoluble compounds with other elements in the soil solution, and they literally fall out of the solution like rain - thus the term 'precipitation'.

When you start adding up all the negatives associated with soils that don't allow you to water properly, it starts to become easier to see why I'm constantly harping on soil choice as the most significant influence on a grower's ability to consistently produce healthy material. The upward creep of pH is one of the negatives on the list

The fact that different genera/species of plants grow in different types of soil (pH) does not necessarily mean that the plant is an 'acid lover' (as an example). It just means that the plants have developed strategies to adapt to certain conditions, like excesses and deficiencies of particular nutrients. Plants that "love" acid soils have simply developed strategies to cope with those soils. Their calcium needs are still the same as any other plant and no different from the nutrient requirements of plants that thrive in alkaline soils. The problem for acid-loving plants is that they are usually unable to adequately limit their calcium uptake, and will absorb too much of it when available, resulting in cellular pH-values that are too high. Some acid-loving plants also have difficulties absorbing Fe, Mn, Cu, or Zn, which are more tightly held in alkaline soils, another reason why they thrive in low pH (acid) soils.

Al