Hydrated Lime is used to minimize odors, typically in outhouses. This product is not generally used as a soil amendment.
Hydrated lime works faster than limestone or dolomitic lime to raise pH levels, but the process can take from several months to a couple of years to finish the job. Other types of lime take even longer, but there is a tradeoff: hydrated lime is more caustic than other types.
Unlike products formulated to lower soil pH, hydrated lime may be integrated into the soil at any time of the year. Amend the soil two or three months before planting to give the lime time to sweeten the soil. Lime may be spread on top of the soil any time of the year and left to penetrate on its own over time, but that process will take longer. Hydrated lime can burn the roots of turfgrasses and should not be used on established lawns. If a soil test taken in the fall indicates that lime is needed, apply it immediately or in winter.
How to Apply Lime
Lime must be incorporated into the soil for best results. The University of California Cooperative Extension recommends tilling lime into the soil to a depth of 7 inches. Apply 3.5 pounds of hydrated lime to every 70 square feet of garden to raise the pH level one point. Work the lime into the soil by hand, with hand tools or a tiller, then water as usual. Hydrated lime should not be mixed with fertilizers or other garden chemicals. To apply lime to individual plants, loosen the soil around the plants carefully to avoid injuring roots and work the hydrated lime into the soil with your hands or a small gardening trowel. Potted plants may also benefit from an annual application of lime. Add 1 tablespoon of hydrated lime to 1 gallon of water, and water as usual.
In small garden beds, you can estimate the amount of lime you need with the following information. These figures refer to the amount of finely ground limestone needed to raise the pH of 100 square feet of soil one point (for example, from 5.0 to 6.0). Sandy loam soil -5 pounds Medium loam soil – 7 pounds Heavy clay soil – 8 pounds How and When to Add Lime You’ll begin to see a measurable difference in the soil pH about four weeks after adding lime, but it can take six to 12 months for the lime to dissolve completely. You won’t see the full effect of adding lime to the soil until it is completely dissolved and incorporated into the soil. For most gardeners, fall is a good time to add lime. Working lime into the soil in the fall gives it several months to dissolve before spring planting. To add lime to the soil, first prepare the bed by tilling or digging to a depth of 8 to 12 inches. Spread the lime evenly over the soil, and then rake it in to a depth of 2 inches.