Soil
Most Nutrient Deficiencies Are pH Problems, Not Shortages
Feeding a yellowing plant more iron rarely works: at the wrong pH, the iron already present is chemically locked away.
Nutrient availability is a function of soil chemistry. Above about pH 7.5, iron and manganese precipitate into forms roots cannot absorb; below pH 5.5, phosphorus binds with aluminium and iron instead. The nutrient is in the soil, just not in solution.
This is why blueberries yellow in chalky ground and why a soil test beats a fertiliser purchase. Most vegetables sit happily between pH 6.0 and 7.0, which is also where the widest range of nutrients stays available.
Put this into practice
- Raised Bed Soil CalculatorHow much soil do I need to fill my raised bed?
- Composting CalculatorWhat ratio of greens to browns does my compost need?
More facts like this
- Topsoil, Garden Soil, and Potting Mix Are Not InterchangeableFilling a raised bed with bagged topsoil is the most common reason a new bed compacts into a brick by its second season.
- Used Coffee Grounds Are Close to pH NeutralSpreading spent coffee grounds will not acidify soil for blueberries or hydrangeas — the acid left with your coffee.
- Adding Sand to Clay Soil Can Make It Worse, Not BetterMixing sand into heavy clay without enough of it, or the wrong grade, produces a denser material than the clay alone — the concrete-mix ratio, essentially.