Rebuild garden soil with application of lime, gypsum

If home garden production seemed a bit off this year, your garden soil may need help. Rebuild it with an application of lime or gypsum.

Liming garden soils west of the Cascades helps the soil in many ways, said Jan McNeilan, Oregon State University Extension Service consumer horticulture agent.

Adding lime neutralizes soil acidity; supplies calcium and magnesium; promotes root growth; creates an excellent environment for soil organisms that break down organic matter; and improves soil structure, McNeilan said.

Lime is recommended for western Oregon gardens because many soils west of the Cascades have high acidity ratings. Soils in the eastern part of the state are not high in acidity, and so will get more benefit from an application of gypsum. Gypsum adds the nutrients sulfur and calcium to garden soils.

Lime can do a lot for soil but it can't alter a heavy clay or compacted soil, said McNeilan. Gypsum can modify a clay soil, but only over a long period of time. The addition of organic matter is the best way to improve heavy clay soils.

Useful organic materials include compost, sawdust, barkdust, leaf mold, and peat moss. Barnyard manures are good, but must be free of symphylans, insect pests that are difficult to get rid of once they become established in garden soil.

Fresh manure is more likely to be free of symphylans than older, rotted manures, said McNeilan.

Apply organic matter in a layer of two to four inches or deeper. Mix this layer with the top six inches of soil.

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Jan McNeilan

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