Soil & Soil Mediums April 4, 2014

Soil Soil is made up of sand, silt, clay, organic matter, living organisms, and pore spaces that hold water and air. Soils vary greatly in composition based on their origin Form as a result of rock breaking down over thousands of years Form as a result of material deposited by wind or water Soils are classified according to the percentage of sand, silt, and clay contained in the mixture Soil particles vary greatly in size Sand – silt – clay

Sandy Soil Sandy or light soil In sandy soils, silt & clay make up less than 20% of the material Soils have large pore space Drain well because gravity forces water down through the pores Little water holding capacity Little capacity to hold plant nutrients Warm up very quickly in the summer

Silt Soils Comprised of intermediate sized particles Fairly fertile soils Well-drained But hold more moisture than sandy soils Easily compacted

Clay Soils Heavy soil Poor drainage and aeration capabilities Small poor space Water and air have a hard time passing through Water is held in the soil Some clay tends to be good for plant growth because it holds moisture & nutrients Takes a long time to warm up in the summer but dries out in high heat Compact and become extremely hard

Loams Most desirable soil type Equal parts of sand, silt, and clay Well-drained soils Optimum moisture & nutrient holding capacity capacity

Soil Mediums

Planting Mediums More and more growers are using planting mixes that contain little, if any soil Advantages The mix is uniform (does not vary in pH or texture) The mix is sterile (containing no disease organisms, insects, or weed seeds) Lighter in weight and easier to handle Good moisture retention & drainage Disadvantages Needs to be stored Some plants prefer natural soils Added expense

Perlite Gray-white mineral of volcanic origin Used to improve aeration Larger particles

PeaT MOSS Partially decomposed vegetation that has been preserved underwater Originates in marshes, bogs, or swamps It has a VERY high moisture holding capacity

Vermiculite Made from mica (mineral) particles Very light material Spongy Neutral pH pH scale is from 0…...7…..14 When vermiculite is heated it expands High moisture holding capacity

Rockwool Manmade fibers made from natural or synthetic minerals Used in hydroponic applications Cultivating plants in mineral solutions (water with added minerals) Has limited water holding capacity which allows water to circulate through the medium