Dirtmechanic
Garden Addicted
Most plant “nutrient problems” are not shortages.
They’re access problems.
Plants are built mostly from carbon, oxygen, and hydrogen (from air and water). Mineral nutrients matter, but they only work after the soil allows roots to breathe, drink, and function. Compaction, poor drainage, pH lockout, and nutrient antagonism will defeat any fertilizer plan—organic or synthetic—every time.
Use the reference below to diagnose failure modes, not just deficiencies.
Ask in this order:
Can roots breathe? (structure, oxygen)
Can roots drink evenly? (water flow, transpiration)
Is pH allowing access? (not just presence)
Are nutrients balanced, or blocking each other?
Only then: is something actually missing?
If your soil test says “adequate” but plants disagree, believe the plants.
Presence ≠ availability.
Rule of thumb:
Plants don’t starve first — they suffocate, dehydrate, or get locked out.
Winter is for thinking clearly so summer doesn’t have to be chaotic.
MAJOR NUTRIENTS (STRUCTURAL / NON-MINERAL)
Carbon (C)
• Soil reaction: Neutral
• Common forms: CO₂ (air), organic matter, compost, biochar
• Primary control: Environment
• Common failure mode: Low photosynthesis (shade, cold, imbalance)
Hydrogen (H)
• Soil reaction: Neutral
• Common forms: Water (H₂O), soil moisture
• Primary control: Environment
• Common failure mode: Drought stress, poor water retention
Oxygen (O)
• Soil reaction: Neutral
• Common forms: Air in soil pores, aeration
• Primary control: Environment
• Common failure mode: Compaction, waterlogging, root suffocation
PRIMARY MACRONUTRIENTS (MINERAL)
Nitrogen (N)
• Soil reaction: Acidifying
• Common forms: Urea, ammonium, nitrates, organic N
• Primary control: Shared (microbes + plant)
• Common failure mode: Leaching, volatilization, microbial tie-up
Phosphorus (P)
• Soil reaction: Slightly acidifying → neutral
• Common forms: Bone meal, phosphates, rock phosphate
• Primary control: Environment-leaning
• Common failure mode: pH fixation (present but unavailable)
Potassium (K)
• Soil reaction: Neutral → slightly alkalizing
• Common forms: Potash, potassium sulfate, kelp
• Primary control: Plant-leaning
• Common failure mode: Antagonism (excess Ca or Mg)
SECONDARY MACRONUTRIENTS
Calcium (Ca)
• Soil reaction: Alkalizing
• Common forms: Lime, gypsum, calcium nitrate
• Primary control: Environment
• Common failure mode: Poor transpiration / uneven water flow
Magnesium (Mg)
• Soil reaction: Alkalizing
• Common forms: Dolomitic lime, Epsom salt
• Primary control: Shared
• Common failure mode: Potassium antagonism, Ca imbalance
Sulfur (S)
• Soil reaction: Acidifying
• Common forms: Elemental sulfur, sulfates
• Primary control: Shared
• Common failure mode: Slow microbial conversion, leaching
MICRONUTRIENTS (TRACE)
Boron (B)
• Soil reaction: Slightly acidifying
• Common forms: Borax, Solubor
• Primary control: Environment
• Common failure mode: Over-application toxicity
Chlorine (Cl)
• Soil reaction: Neutral
• Common forms: Irrigation water, KCl
• Primary control: Environment
• Common failure mode: Salinity stress
Copper (Cu)
• Soil reaction: Slightly acidifying
• Common forms: Copper sulfate, chelates
• Primary control: Environment-leaning
• Common failure mode: Accumulation, microbial suppression
Iron (Fe)
• Soil reaction: Acidifying
• Common forms: Iron sulfate, chelates
• Primary control: Environment
• Common failure mode: High-pH lockout (chlorosis)
Manganese (Mn)
• Soil reaction: Acidifying
• Common forms: Manganese sulfate
• Primary control: Environment
• Common failure mode: High pH, oxidized soils
Molybdenum (Mo)
• Soil reaction: Slightly alkalizing
• Common forms: Molybdates
• Primary control: Environment
• Common failure mode: Low-pH lockout (inverse of iron)
Nickel (Ni)
• Soil reaction: Neutral
• Common forms: Trace presence
• Primary control: Environment
• Common failure mode: Rare toxicity
Zinc (Zn)
• Soil reaction: Slightly acidifying
• Common forms: Zinc sulfate, chelates
• Primary control: Environment-leaning
• Common failure mode: High phosphorus antagonism
I hope this helps someone this season!
They’re access problems.
Plants are built mostly from carbon, oxygen, and hydrogen (from air and water). Mineral nutrients matter, but they only work after the soil allows roots to breathe, drink, and function. Compaction, poor drainage, pH lockout, and nutrient antagonism will defeat any fertilizer plan—organic or synthetic—every time.
Use the reference below to diagnose failure modes, not just deficiencies.
Ask in this order:
Can roots breathe? (structure, oxygen)
Can roots drink evenly? (water flow, transpiration)
Is pH allowing access? (not just presence)
Are nutrients balanced, or blocking each other?
Only then: is something actually missing?
If your soil test says “adequate” but plants disagree, believe the plants.
Presence ≠ availability.
Rule of thumb:
Plants don’t starve first — they suffocate, dehydrate, or get locked out.
Winter is for thinking clearly so summer doesn’t have to be chaotic.
MAJOR NUTRIENTS (STRUCTURAL / NON-MINERAL)
Carbon (C)
• Soil reaction: Neutral
• Common forms: CO₂ (air), organic matter, compost, biochar
• Primary control: Environment
• Common failure mode: Low photosynthesis (shade, cold, imbalance)
Hydrogen (H)
• Soil reaction: Neutral
• Common forms: Water (H₂O), soil moisture
• Primary control: Environment
• Common failure mode: Drought stress, poor water retention
Oxygen (O)
• Soil reaction: Neutral
• Common forms: Air in soil pores, aeration
• Primary control: Environment
• Common failure mode: Compaction, waterlogging, root suffocation
PRIMARY MACRONUTRIENTS (MINERAL)
Nitrogen (N)
• Soil reaction: Acidifying
• Common forms: Urea, ammonium, nitrates, organic N
• Primary control: Shared (microbes + plant)
• Common failure mode: Leaching, volatilization, microbial tie-up
Phosphorus (P)
• Soil reaction: Slightly acidifying → neutral
• Common forms: Bone meal, phosphates, rock phosphate
• Primary control: Environment-leaning
• Common failure mode: pH fixation (present but unavailable)
Potassium (K)
• Soil reaction: Neutral → slightly alkalizing
• Common forms: Potash, potassium sulfate, kelp
• Primary control: Plant-leaning
• Common failure mode: Antagonism (excess Ca or Mg)
SECONDARY MACRONUTRIENTS
Calcium (Ca)
• Soil reaction: Alkalizing
• Common forms: Lime, gypsum, calcium nitrate
• Primary control: Environment
• Common failure mode: Poor transpiration / uneven water flow
Magnesium (Mg)
• Soil reaction: Alkalizing
• Common forms: Dolomitic lime, Epsom salt
• Primary control: Shared
• Common failure mode: Potassium antagonism, Ca imbalance
Sulfur (S)
• Soil reaction: Acidifying
• Common forms: Elemental sulfur, sulfates
• Primary control: Shared
• Common failure mode: Slow microbial conversion, leaching
MICRONUTRIENTS (TRACE)
Boron (B)
• Soil reaction: Slightly acidifying
• Common forms: Borax, Solubor
• Primary control: Environment
• Common failure mode: Over-application toxicity
Chlorine (Cl)
• Soil reaction: Neutral
• Common forms: Irrigation water, KCl
• Primary control: Environment
• Common failure mode: Salinity stress
Copper (Cu)
• Soil reaction: Slightly acidifying
• Common forms: Copper sulfate, chelates
• Primary control: Environment-leaning
• Common failure mode: Accumulation, microbial suppression
Iron (Fe)
• Soil reaction: Acidifying
• Common forms: Iron sulfate, chelates
• Primary control: Environment
• Common failure mode: High-pH lockout (chlorosis)
Manganese (Mn)
• Soil reaction: Acidifying
• Common forms: Manganese sulfate
• Primary control: Environment
• Common failure mode: High pH, oxidized soils
Molybdenum (Mo)
• Soil reaction: Slightly alkalizing
• Common forms: Molybdates
• Primary control: Environment
• Common failure mode: Low-pH lockout (inverse of iron)
Nickel (Ni)
• Soil reaction: Neutral
• Common forms: Trace presence
• Primary control: Environment
• Common failure mode: Rare toxicity
Zinc (Zn)
• Soil reaction: Slightly acidifying
• Common forms: Zinc sulfate, chelates
• Primary control: Environment-leaning
• Common failure mode: High phosphorus antagonism
I hope this helps someone this season!
