What is Gypsum and How Does It Help My Lawn and Garden?

What is Gypsum and How Does It Help My Lawn and Garden?

Prefer to watch instead of reading?
Check out the SoiLab episode, where scientist Matt Williams explains the science behind gypsum and its role in improving soil health, especially for gardeners and homeowners dealing with high-sodium (sodic) soils.

What is Gypsum?

Gypsum is a naturally occurring mineral composed of calcium sulfate (CaSO₄). It serves several important roles in soil management:

·       Soil Amendment: Improves soil structure by promoting aggregation of soil particles.

·       Soil Conditioner: Enhances water movement and root growth, making it easier for plants to access nutrients and water.

·       Fertilizer: Provides calcium and sulfur, both of which are essential plant nutrients.

When Should You Use Gypsum?

Gypsum is recommended when a soil test (such as MySoil) reveals high sodium levels. High sodium soils often show these visual signs:

·       Wilting plants despite adequate watering

·       Powdery soil surface

·       Water pooling or failing to infiltrate

How Does Gypsum Work?

Gypsum’s effectiveness lies in its chemistry:

·       Calcium in Gypsum: The calcium ions in gypsum replace sodium ions on soil particles.

·       Soil Structure Improvement: This process, called flocculation, causes soil particles to clump together, forming larger aggregates. The calcium ions help bind adjacent soil particles, holding them together. These aggregates allow for better water infiltration and air exchange, resulting in healthier plant roots.

·       Sodium Removal: Once sodium is displaced, irrigation washes it out of the root zone, reducing toxicity and improving soil conditions.

Demonstration: Gypsum in Action

Matt on SoiLab demonstrates this process in the lab:

1.      Two samples of sodic soil are prepared-one treated with gypsum, one without.

2.     Water is added to both.

3.     Over 30 minutes, the gypsum-treated soil clears faster as particles clump and sink, visually proving gypsum’s effect on soil structure.

Frequently Asked Questions

·       Does gypsum change soil pH?
No, gypsum does not significantly alter soil pH.

·       Can gypsum replace lime?
No, although both contain calcium, lime raises soil pH while gypsum does not.

·       Will gypsum fix clay compaction?
Not usually. Gypsum is not a universal solution for clay compaction unless high sodium is present; other strategies may be needed.

How to Apply Gypsum

·       Surface Application: Spread gypsum on the soil and irrigate thoroughly.

·       Incorporation: For new beds, mix gypsum into the soil before planting and water well.

·       Irrigation is Essential: Water is needed to move sodium out of the root zone after gypsum application.

Key Takeaway

If your MySoil test recommends gypsum due to high sodium, applying it can dramatically improve water movement, soil structure, and plant health. However, it’s not a cure-all for all soil problems-always base your treatment on soil test results.

For more details, check out the full SoiLab video for a visual demonstration.

Keywords: gypsum, soil amendment, sodium soil, lawn care, garden soil, soil structure, plant health, SoiLab