A standard broadcast spreader is generally not the right tool for applying powdered lime, also known as pulverized limestone. This fine-particulate soil amendment is created by crushing limestone or chalk, and its primary component is calcium carbonate, which neutralizes soil acidity and raises the pH level. Broadcast spreaders, often called rotary spreaders, are engineered to handle granular materials like seeds, fertilizers, or pelletized products. These tools rely on the uniform size and weight of granules, which are dropped onto a spinning plate and flung outward. Powdered lime is highly effective at quickly amending soil, but its physical properties are incompatible with the mechanics of most broadcast spreaders.
Why Powdered Lime Is Unsuitable for Broadcast Spreaders
The fine nature of pulverized lime creates mechanical and safety issues when placed in a rotary spreader. A primary problem is bridging, where the powder compacts under its own weight inside the hopper. This compaction forms an arch over the flow gate, preventing the material from dropping onto the spinning plate. If material initially flows, the powder often hollows out inside the hopper, leaving product stuck to the sides.
Minor moisture, either from the air or residual dampness, can cause the powder to clump, blocking the metering orifice and gear mechanisms. When the fine powder exits the hopper, the slightest breeze causes it to become airborne. This results in a significant, uncontrolled dust cloud, leading to highly uneven distribution and product waste. This excessive dust also poses a safety hazard for the user and surrounding environment.
The Difference Between Lime Types
Understanding the different forms of agricultural lime is key to efficient spreading, as they are categorized by particle size. Pulverized lime is the cheapest and fastest-acting form because its small particles have a large surface area for rapid reaction with the soil. A coarser option is granular lime, which is crushed limestone with a larger particle size, similar to coarse sand. The third form is pelletized lime.
Pelletized lime is created by compressing finely ground lime into small, uniform pellets using a binding agent. This transforms the difficult-to-handle powder into a material that flows like granular fertilizer or seed. The pellets resist bridging and clumping, allowing them to flow evenly through the metering system of a broadcast spreader. Once applied, the pellets quickly dissolve upon contact with moisture, dispersing the lime and providing the same rapid pH correction as the powdered product.
Alternative Tools for Applying Pulverized Lime
If a user possesses powdered lime and cannot switch to a pelletized version, alternative methods exist, though they are often more labor-intensive or require specialized equipment. A drop spreader is a better option than a broadcast spreader because it releases the material straight down between the wheels, mitigating the dust cloud and uneven spread. However, even a drop spreader will struggle with the material’s tendency to bridge and clog the narrow flow gate, requiring frequent agitation to maintain flow.
For large-scale application, specialized commercial lime spreaders are designed with heavy-duty agitators and wider conveyor belts to handle the flow issues of powdered limestone. For the average homeowner, a low-cost manual technique is to mix the powdered lime with a bulk material like dry sand or topsoil to create a temporary, coarse-textured blend. This mixture can then be applied with a shovel or scoop, or loaded into a drop spreader. When handling powdered lime, wear appropriate respiratory protection and goggles to guard against inhaling the fine dust particles, which can be caustic.