Soil amendment

A material added to soil to change its physical properties, nutrient content, or chemical conditions. Amendments can improve growing conditions or address specific soil problems.

Compost: Decomposed organic matter used to enrich soil and support its structure and biological activity. Adds organic matter and nutrients while improving water retention in many soils.
Soil structure: The arrangement of soil particles into aggregates and the pores between them. Organic amendments can support aggregation, changing aeration, infiltration, and root growth.
Soil testing: The analysis of soil samples to estimate properties such as pH, nutrient levels, and salinity. Test results help identify which soil condition an amendment should address.
Fertilizer: A natural or manufactured material applied to supply one or more nutrients to plants. Fertilizers primarily supply nutrients; amendments may instead target soil structure or chemistry.
Lime (material): Calcium- or calcium-and-magnesium-containing material applied to soil, commonly to reduce acidity. Raises soil pH when acidity limits nutrient availability or crop growth.
Cation-exchange capacity: A measure of soil's capacity to retain and exchange positively charged ions. Clay and organic matter amendments can alter how soil holds nutrient cations.
Plant nutrient: A chemical element or compound required for plant growth and development. Nutrient amendments are useful only when their supply matches plant requirements.
Soil conditioner: A material added to soil to improve physical properties such as structure, aeration, or water retention. The term overlaps with soil amendment but emphasizes physical improvement.
Gypsum: A mineral composed of calcium sulfate dihydrate, used in agriculture as a soil amendment and calcium source. Can supply calcium and help reclaim some sodic soils without substantially raising pH.
Soil pH: A measure of the acidity or alkalinity of soil solution. Chemical amendments such as lime change pH and thereby affect nutrient availability.

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