How does soil pH affect fertilizer effectiveness?

Soil pH is a major nutrient gatekeeper that significantly influences the efficiency of fertilizers. In acid soils with a pH of less than 6.0, phosphorus becomes bound with aluminum and is rendered valueless to plant life. The plant-available calciums are similarly reduced in availability, thereby causing blossom end rot in tomatoes and similar fruits. In alkaline soils with pHs above 7.5, the iron becomes tied up, and yellow leaves are often the result. Unless soil pH is established within the correct balance, the money invested in fertilizers is usually wasted.

Nitrogen fertilizers react differently depending on the soil pH. Where ammonium forms are used, soil acidification occurs, which reduces their efficiency over time. Nitrate fertilizers often yield better results when the soil is alkaline, but they also leach out more readily. Urea falls into the category of substances that thrive best in almost neutral soil pH conditions. I adjust my nitrogen fertilizers annually based on the results of my soil tests.

To maximize efficiency, adjust pH before fertilizing. Apply lime to acidic beds four weeks before adding phosphorus fertilizers. Incorporate sulfur into alkaline soils before utilizing iron-rich supplements. This sequence prevents nutrient lockout. I test the pH, then select the fertilizers required to achieve the proper pH.

Organic matter buffers pH extremes, improving fertilizer uptake. Compost maintains nutrient availability across wider pH ranges than synthetic fertilizers. I add compost quarterly to stabilize the chemistry of my garden. This reduces fertilizer needs while protecting plants from pH fluctuations.

Read the full article: Soil pH Testing: The Complete How-To Guide