Oregon Soil Amendment Services

Lime raises soil pH and adds calcium, making it the choice for acidic soils, while gypsum adds calcium and sulfate without changing pH. Gypsum is widely used in California to improve water infiltration and displace sodium in heavy or sodic soils. Soil test results determine which one a field actually needs.

Gypsum rates are set from a soil test, but annual applications generally should not exceed about 5 tons per acre, with many fields using 1 to 2 tons. The right amount depends on cation exchange capacity, sodium levels, and the goal, whether infiltration or sodium removal. A finely ground product spreads and reacts more evenly.

Compost adds organic matter that improves soil structure, water-holding capacity, and microbial activity, and it supplies slow-release nutrients. It helps sandy soils hold moisture and helps clay soils drain and resist compaction. Benefits build over repeated applications rather than from a single pass.

Most amendments are best applied before planting or during the dormant or off season so they can react with the soil and, where helpful, be incorporated. Lime in particular needs time and moisture to change pH. Timing also depends on the crop, the amendment, and field access between rotations.