How to Use Gypsum on Clay Soil?

Gypsum is a useful soil amendment for improving clay soil structure, drainage, and aeration. Here's how to effectively apply it:

1. Preparation is Key

Before applying gypsum, it's helpful to understand why you're using it. Gypsum (calcium sulfate) helps to displace sodium ions in clay soil, which cause compaction. This allows clay particles to flocculate (group together), creating larger pore spaces for better water and air movement.

2. Application Methods:

There are two main approaches to applying gypsum, depending on whether you have an existing lawn or are preparing a new planting area:

• For Existing Lawns Suffering from Compaction:

  1. Aerate: This is crucial. Aeration creates holes in the soil, allowing the gypsum to penetrate more effectively. You can use a core aerator or a spike aerator.
  2. Spread Gypsum: Evenly distribute gypsum over the lawn at a rate of 1-2 kg per square meter.
  3. Rake In: Gently rake the gypsum into the aerated holes.
  4. Water Heavily: Water the lawn thoroughly to help the gypsum dissolve and move into the soil.

• If Aeration Isn't Possible:

  1. Spread Gypsum: Distribute gypsum over the affected area, again at a rate of 1-2 kg per square meter.
  2. Water Heavily: Immediately after spreading, water the area very heavily to help the gypsum penetrate the soil. This method is less effective than aerating first, but it's better than nothing.

3. Best Practices:

• Timing: The best time to apply gypsum is in the fall or early spring.
• Even Distribution: Ensure even coverage for consistent results. Using a spreader can help with this.
• Soil Testing: While not always necessary, a soil test can help you determine the exact amount of gypsum needed. Over-application is possible and could lead to nutrient imbalances.
• Follow-Up: Consider reapplying gypsum annually or bi-annually, especially if the soil is heavily compacted.

4. Expected Results:

You should start to see improvements in soil structure and drainage over time. It may take several months to see significant changes. Look for signs like improved water infiltration, less surface runoff, and healthier plant growth.