Which of the following is a negative effect of soil acidity?

Soil acidity can significantly impact plant health and growth, and one of the negative effects is reduced root growth. When soil pH drops, it can lead to an increased concentration of hydrogen ions, which can harm the soil environment for roots. Acidic conditions can hinder the uptake of essential nutrients, such as nitrogen, phosphorus, and potassium, which are vital for the development of roots. Additionally, lower pH levels can result in the solubilization of toxic metals like aluminum, which can further damage the root system and restrict growth.

In contrast, increased nutrient availability is generally a positive aspect of certain conditions but not specifically related to soil acidity alone. Likewise, decreased aluminum toxicity and improved soil microorganism function are conditions that may arise under more neutral or alkaline soil pH rather than in acidic soils. Thus, reduced root growth directly illustrates the negative consequences of soil acidity on plant health.