Soil, Media, and Plant Nutrition
What the domain covers
This domain tests soil as a living root medium and the management of media and nutrients for garden plants. Expect questions on texture, pH, organic matter, growing media, essential nutrients, and deficiency diagnosis.
Core rules and concepts
- Soil texture is the sand, silt, and clay proportion; structure is how particles aggregate. Loam balances drainage and water holding.
- Soil pH controls nutrient availability. Most garden plants grow best near pH 6.0–7.0; acid-loving plants such as azalea need lower pH.
- Growing media may mix soil, sand, cocopeat, compost, perlite, or vermicompost; they must drain yet retain moisture.
- Macronutrients are N, P, K, Ca, Mg, S; micronutrients include Fe, Zn, Mn, B, Cu, Mo, Cl.
- Nitrogen supports leaf growth; phosphorus supports roots and flowering; potassium supports fruit quality and stress tolerance.
- Apply organic matter before planting and split fertilizer doses; more is not better.
Worked example
Tomato seedlings in sandy soil show pale older leaves, thin stems, and slow growth, while new leaves remain fairly green. Nitrogen is mobile, so the plant moves N to young tissue and older leaves yellow first. Sandy soil also leaches nitrate. The reasoned response is compost or well-rotted FYM plus a split nitrogen dose, not a blind increase of all fertilizers.
Traps
- Blaming disease for every yellow leaf: check lower versus upper leaves and soil moisture first.
- Ignoring pH: iron can be present yet unavailable in alkaline soil.
- Using fresh manure: it can burn roots and carry weed seeds.