a rabe power harrow

What Does a Power Harrow Do?

Welcome back to GrowerExperts, your go-to site for all things farming! Today, we’re focusing on a key piece of farming equipment: the power harrow. This tool is central to preparing the perfect seedbed for your crops.

The Invention of the Power Harrow

The power harrow was invented by Willy Becker in Germany in the late 1950s. Becker realized that farmers needed a more efficient way to prepare their fields for planting, leading to the creation of this innovative tool. The power harrow quickly gained popularity for its effectiveness and efficiency, revolutionizing agriculture worldwide.

What does a power harrow do?

A power harrow is a type of agricultural implement used for breaking up, refining, and distributing soil to create an ideal seedbed. It’s a significant upgrade from traditional harrows because it’s more efficient at preparing the soil for planting, thanks to its rotating blades or tines.

How does a power harrow work?

The core component of a power harrow is the rotor. Each rotor is equipped with a set of vertically aligned blades or tines that spin at high speed when the harrow is in operation. These blades dig into the soil, breaking it up and aerating it.

Unlike a plough, which turns the soil over completely, a power harrow mixes the soil, breaking up clods and surface crust while keeping the soil layers largely intact.

The gear trough of a power harrow with the top cover removed to show the internal rotor drive gears
The gear trough of a power harrow with the top cover removed to show the internal rotor drive gears.

Usually, there are two tines fixed to one rotor, and each rotor is connected to the next rotor via a large gear across the width of the power harrow.

Adjusting the working depth

The working depth of a power harrow is adjustable via the tractor three-point linkage and rear depth roller, allowing the farmer to control how deeply the tines penetrate the soil. This can be adjusted based on the type of crop being planted and the specific needs of the soil.
a rabe power harrow side view showing the rear depth roller
The adjustable depth roller at the rear of a power harrow also breaks clumps of soil, levels and compresses the soil to lock in moisture.

At the back of the power harrow, there is typically a roller. As the power harrow moves across the field, the roller flattens the soil behind it, creating a level, even surface.

This roller also helps control the working depth of the tines – the deeper the roller is set, the deeper the tines will work.

An effective tool against forming a hardpan in the soil

A hardpan is a compacted, dense layer of soil that can form beneath the topsoil’s loose layer.

This can occur due to continuous ploughing or tilling in a horizontal plane at the same depth, compressing the soil below and making it nearly impervious to water and plant roots.

This hard layer can be detrimental to plant growth, as it restricts roots from penetrating deeper into the soil, limiting access to nutrients and water.

The power harrow is designed to combat the formation of a hardpan in a few key ways:

1. Variable Tilling Depth: Power harrows allow for the adjustment of tilling depth.

By varying the depth of tilling from season to season, the risk of hardpan formation is significantly reduced. This is because the soil isn’t being compacted consistently at the same depth, which is a common cause of hardpan formation.

2. Vertical Soil Handling: Unlike some other tilling machines, power harrows don’t invert or turn over the soil in a horizontal plane.

Instead, they stir the soil in a vertical plane, keeping the soil structure more intact. This action reduces the risk of soil compaction, thus minimizing the chance of hardpan formation.

showing the blades of a power harrow in a vertical plane.
The blades/tines of a power harrow are mounted vertically, and turn in a circular motion.

3. Soil Aeration: Power harrows effectively aerate the soil as they work. This helps maintain a healthy soil structure, promoting better drainage, and reducing soil compaction.

Minimizing the spread of weeds

The way a power harrow operates can indeed help minimize the spread of weed seeds, especially compared to a rotovator.

A rotovator, also known as a rotary tiller, works by a series of blades that are attached to a rotor which spins in a horizontal plane. These blades dig into the soil and turn it over completely.

This churning action can bring dormant weed seeds to the surface, where they are exposed to sunlight and water, conditions that can trigger germination. As a result, rotovating can inadvertently lead to a proliferation of weeds in your field.

a rotovator showing the blades in a horizontal fashion
The horizontally configured blades of a tractor-mounted rotovator.

On the other hand, a power harrow operates differently. While it does effectively break up and aerate the soil, it doesn’t turn the soil over like a rotovator. Instead, it stirs the soil in a vertical plane, maintaining the existing soil layers.

This is beneficial for a couple of reasons:

1. Weed Seed Burial: By not inverting the soil, power harrows leave weed seeds buried deep in the soil where they are less likely to germinate. The weed seeds that are already on or near the surface can germinate, but they are then destroyed by the following harrowing or other weed control practices.

2. Preservation of Soil Structure: The action of the power harrow also helps to preserve the structure of the soil. This not only aids in preventing soil erosion but also helps maintain the natural biological activity in the soil, such as worms and other bugs and insects which can contribute to the suppression of weeds.

Uses of Power Harrows in Agriculture

The power harrow is a versatile tool that can be used for soil preparations in a variety of crops, but its effectiveness can vary depending on the crop and the soil conditions.

Power Harrows for Seedbed Preparation in Cereal Crops

Power harrows are particularly effective when it comes to preparing seedbeds for cereal crops such as wheat, barley, or oats. These crops require a well-prepared seedbed for optimal germination and growth, and that’s where the power harrow shines.

The power harrow in this combination drill makes a perfect seedbed for the oats being sown.

The power harrow works by mixing the soil, creating a consistent and level seedbed. The rotating tines break up clods and aerate the soil, improving its structure and preparing it perfectly for the sowing of cereal crops.

Moreover, the depth control of a power harrow ensures that the seedbed is created at the ideal depth for cereal crops. This consistency in depth helps to ensure uniform crop emergence, which is crucial for maximizing yield in cereal crops.

Power Harrows and Vegetable Crops: The Potato Example

When it comes to certain vegetable crops, such as potatoes, power harrows may not be the most suitable choice for a few reasons.

Firstly, potatoes require a very fine tilth – a soft, fine-textured surface layer of soil. While power harrows do break up the soil, they may not always create the extremely fine tilth that potatoes need for optimal growth.

Secondly, potatoes are typically planted deeper than cereal crops. A power harrow might not till as deeply as necessary for potatoes.

Lastly, potatoes, being tuber crops, need soil that has been turned over, allowing tubers to develop without being obstructed. A power harrow mixes and stirs the soil vertically rather than turning it over as a rotovator would do, which may not be ideal for potato cultivation.

How Forward Speed, Rotor Speed and Depth Affects Soil Tilth

When operating a power harrow, there are three key factors that can significantly impact the quality of soil tilth: forward speed, rotor speed, and working depth.

1. Forward Speed

The forward speed refers to how quickly the power harrow is moving across the field. This speed can influence the thoroughness of the tilling and the texture of the resulting tilth.

  • Slow Speed: When the power harrow moves slowly, it spends more time in contact with the soil. This leads to more thorough tilling and a finer tilth. However, it also means that field preparation takes more time, which may not be efficient for larger fields.
  • Fast Speed: On the other hand, a faster forward speed means that the harrow spends less time in contact with each section of the soil. This can result in less thorough tilling and a coarser tilth, but it allows for faster field preparation.

2. Rotor Speed

The rotor speed refers to how fast the tines of the power harrow are spinning. The speed of the rotors can impact the size of the soil particles in the tilth and the uniformity of the soil mixing.

  • High Rotor Speed: When the rotors spin at high speeds, they break up the soil more effectively, resulting in a finer and more uniform tilth. This is beneficial for crops that require a fine seedbed. However, higher rotor speeds can also increase fuel consumption and wear on the machine.
  • Low Rotor Speed: Lower rotor speeds result in less aggressive soil breaking, leading to a coarser tilth. This may be suitable for certain crops or soil conditions, and it can also help reduce fuel consumption and machine wear.

3. Working Depth

The working depth of a power harrow refers to how deeply the tines penetrate into the soil. The depth of tilling can influence the soil structure and the suitability of the resulting seedbed for different crops.

  • Deep Tilling: Deep tilling can help break up compacted layers of soil, improving soil structure and drainage. This can be beneficial for crops that require deep-root penetration. However, deep tilling can also bring dormant weed seeds to the surface and increase the risk of soil erosion.
  • Shallow Tilling: Shallow tilling creates a finer tilth in the top layer of soil, which can be ideal for crops with shallow roots or for the sowing of small seeds. It also helps preserve soil moisture and reduces the risk of bringing dormant weed seeds to the surface.


Power harrows have revolutionized farming, making the process of preparing a seedbed faster, easier, and more efficient. As with any tool, it’s essential to understand how they work, their benefits, and their limitations. Keep exploring our site for more insights into the tools that make modern farming possible.

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