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Plant Environment: Soil

Plant Environment: Soil. Components of soil. Weathered rocks (particles). Soil. Decomposing organic matter. Spaces containing water an air. Living organisms (particularly bacteria, fungi, protists). Functions for plants. Substance in which to anchor plants.

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Plant Environment: Soil

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  1. Plant Environment: Soil • Components of soil • Weathered rocks (particles) • Soil • Decomposing organic matter • Spaces containing water an air • Living organisms (particularly bacteria, fungi, protists) • Functions for plants • Substance in which to anchor plants • Source of mineral elements (except C) • Source of water and oxygen

  2. Plant Environment: Soil • Mineralsoils = soils with less than 20% organic matter • Texture characteristics • Mineral soil • Based on relative amounts of sand, silt and clay • Sand: large mineral particles (course grain) • Silt: medium mineral particles (medium grain) • Clay: small, flat mineral particles (fine grain)

  3. Plant Environment: Soil • Texture types used for horticulture • Sand (> 70% sand) • Mineral soil • Water drains through quickly; vulnerable to drought • Little organic matter • Lose nutrients quickly • Sandy loam (> 50% sand with remainder silt and clay) • Enough silt and clay to hold water and nutrients • Warm quickly in spring (used for early-season crops)

  4. Good for apples Plant Environment: Soil • Texture types used for horticulture • Loam (about same amount of all particle types) • Mineral soil • Good drainage, but with adequate nutrient and water retention • Horticulturally productive soils • Silt Loam (> 50% silt, remainder sand and clay) • Smooth, flour-like soil • Hold large amounts of water

  5. Plant Environment: Soil • Texture types used for horticulture • Clay (> 50% clay, remainder sand and silt) • Mineral soil • Poor drainage, poor aeration, easily compacted • Poor for horticultural production

  6. Plant Environment: Soil • Texture and water movement • Water moves between soil particles down through soil • Mineral soil • Abrupt changes in soil texture stop flow of water through soil • Water accumulates above change in texture (= perchedwatertable) • Perched water table inhibits root growth (no oxygen) • Avoid perched water tables by mixing different soil textures (for potted plants, transplanting trees)

  7. Plant Environment: Soil • Soil with more than 20% organic matter • Muck soil (highly decomposed) • Organic soils • Peat (slightly decomposed) • Usually formed under long-term conditions of excess moisture • sphagnum peat main component of potting mixes • Greatly improved water holding of soil

  8. Plant Environment: Soil • Soil pH not constant; changes with fertilizers, irrigation • Soil pH • soil pH influences plant growth by: • Altering nutrient availability (e.g. several micronutrients most soluble at low pH; several macronutrients least soluble at low pH) • Influencing soil microorganisms (e.g. potato grown in acidic soil to escape fungal pathogen) • Direct effects of acidification (most plants can tolerate relatively low soil pH)

  9. Plant Environment: Soil • Effective ways to prevent erosion of topsoil and leaching of nutrients • Soil management • Plant cover crops in winter • Maintain wind breaks; trees and shrubs along edges of agricultural fields • Special planting methods such as contour planting, terracing on slopes, no tillage, mulches

  10. Plant Environment: Soil • Most field soils not appropriate for containers • Not free of toxic substances and undesirable organisms • Media used in containers • Become compacted with repeated waterings • Soilless potting mixes used in most greenhouses: • Sphagnum peat • Partly decomposed bark • Vermiculite • Perlite

  11. Plant Environment: Soil • Advantages of using mulch • Water conservation (reduce evaporative water loss) • Mulch • Weed control • Temperature modification (reduce temperature fluctuations) • Protect soil from erosion • Improve soil structure as mulch decays • Retain nutrients • Reduce some insect pests (aphids avoid white plastic mulch) • Hydroseeding of turf

  12. Plant Environment: Soil • Nonorganic • Plastic sheeting • Types of Mulch • Black used to prevent growth of weeds and heat soil • Used for high-value crops (e.g. strawberries, tomatoes) • Organic • Straw, wood chips, shredded bark, dry pine leaves • Provides organic matter as decomposes; aggregates soil particles and improves drainage and aeration (but must add N for microbes) • Blocks light and therefore controls weed growth • Reduces soil erosion and nutrient leaching • Reduces soil temperature

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