Certified Crop Advisor Practice Exam

Lime passing through which of the following mesh sizes would be most effective in neutralizing soil acidity?

1. 20 mesh

2. 40 mesh

3. 60 mesh

4. 80 mesh

The correct answer is: 60 mesh

The effectiveness of lime in neutralizing soil acidity is significantly influenced by its particle size. Finer particles have a larger surface area which allows for more effective interaction with soil particles and acids. Lime that passes through a 60 mesh sieve has a particle size that is small enough to ensure a greater surface area is available for reaction. This increased reactivity means that it can neutralize soil acidity more effectively than coarser materials, such as lime that passes through a 20 mesh or 40 mesh sieve. The efficiency of lime application also typically decreases with larger mesh sizes because larger particles dissolve more slowly, limiting their ability to modify pH levels in the soil promptly. Therefore, lime that passes through an 80 mesh sieve would be even finer than 60 mesh, potentially increasing effectiveness, but the options presented suggest that 60 mesh is often considered the most beneficial grade for practical applications regarding neutralizing acidity. In summary, lime that passes through a 60 mesh size effectively balances the need for particle size and surface area for optimal interaction with soil acidity, making it the most reliable choice for this purpose.