Is Gypsum Better for a Garden Than Lime?

Gypsum Benefits

• Gypsum is calcium sulfate. It provides garden soil and the plants grown there with calcium and sulfur, and both are necessary for plant growth. Gypsum does not change soil pH, meaning it can be used on soils where the pH is already balanced properly for the plants that are growing there. Gypsum also helps relieve plants plagued by salty soils, since it reacts with the salt, changes its structure and allows it to leach away. Given enough time, gypsum can improve the drainage problems inherent in heavy clay soils.

Lime Benefits

• Lime sold as a garden amendment is either calcium carbonate or calcium magnesium carbonate. Both are alkaline materials and will help neutralize soils that are too acidic for the plants that will be grown there. Both have high amounts of calcium, which plants need for structure. Calcium magnesium carbonate, or dolomite lime, also contains another important plant nutrient, magnesium.

Gypsum Drawbacks

• Gypsum won't help rectify acidic soils. It also is not as useful in amending poorly drained soils as compost is. Neither will gypsum work in poorly drained silt or sand soils.

Lime Drawbacks

• Using lime in alkaline or neutral soils throws off the pH balance of the garden soil, making it inhospitable to many plants. Some plants also respond poorly to excess magnesium in the soil, meaning that applying dolomite lime when the soil already has sufficient or excess magnesium is harmful to garden plants. Lime does not correct poorly drained soils.

Considerations

• If a soil test reveals that the soil is too acidic for the plants that grow there, with poor calcium and little nutrition, lime is the best choice for that garden. If a soil test reveals that the soil is heavy clay, has a neutral or alkaline pH, has poor calcium and perhaps even has excess salts, gypsum is the better choice.