The amount of water held in soil pores, ranging from permanent wilting point (too dry for plants) through field capacity (optimal holding) to saturation (waterlogged).
In plain terms
Soil moisture exists on a spectrum. Permanently wilted: soil too dry, plants wilt, can't recover. Wilting point: plants can't extract water. Field capacity: optimal moisture for plant growth (water drains away but adequate remains). Saturation: waterlogged, roots can't breathe. Good gardening keeps soil in the field capacity range—moist but draining.
Why this matters
Understanding soil moisture helps you water properly. Too wet and roots rot; too dry and plants wilt; both reduce growth.
In practice
Examples
Soil at field capacity: moist, dark, holds together but crumbles; ideal.
Too wet: puddles, waterlogging, musty smell; drainage problem or overwatering.
Too dry: pale, hard, pulling away from edges of container; needs water.
Well-watered soil: crumbly, dark; supports healthy root growth and microbes.
Practical applications
Check soil moisture before watering; stick finger in soil, water if dry below top inch.
Deep, infrequent watering maintains field capacity longer.
Mulch retains moisture and moderates fluctuations.
In containers, well-draining mix prevents waterlogging despite frequent watering.
Monitor soil moisture in hot weather; increased evaporation requires more frequent checking.