Quality of peat substrates for plants grown in containers

Peat materials are widely used in growing media for nursery and greenhouse productions. Tillage of peat fields as well as harvesting, piling, screening, crushing, and handling operations influence particle size distribution and peat quality without influencing decomposition degree. Quality attributes of peat-base products are physical (air-water storage and exchange), and chemical (pH, salinity, and nutrient content). Determination methods are briefly described. Total porosity, air-filled porosity, storage capacity for available water, and container capacity are associated with peat degree of decomposition and botanical makeup. Pore tortuosity and gas diffusivity are more closely related to grain-size distribution and plant productivity than capacity criteria such as air-filled porosity and volume of available water. Structuring components to be combined with peat materials should increase gas diffusion while maintaining high amounts of available water. Nutrient availability is primarily related to substrate pH, salinity, and cation exchange capacity. Fibric and hemic Sphagnum peat and some herbaceous peat materials are used successfully in peat mixes.