GACIL® · CROP NUTRITION GUIDE
Start with leaf age. Then look at the veins.
Yellow leaves on plants can be a sign of nutrient deficiency, but they can also follow watering problems, root damage, pests or normal ageing. Compare the patterns below to decide what to check next.
For farmers and gardeners: a practical comparison of nitrogen, magnesium and iron deficiency.
THE QUICK READ
Why do leaves turn yellow?
- Leaf yellowing is called chlorosis. Reduced chlorophyll makes the leaf look pale green, yellow or almost white.
- Leaf position is a useful clue. A shortage of mobile nutrients such as nitrogen or magnesium often shows on older leaves first. Iron-related chlorosis is usually most evident in new leaves.
- Check the cause before feeding. Compare symptoms with irrigation, drainage, soil pH and fertilizer history; a soil or tissue test can help resolve uncertainty.
OBSERVE TWO THINGS
Compare the typical leaf patterns
RULE 01
Which leaves changed first?
- Older, lower leaves: compare nitrogen and magnesium patterns.
- New, upper leaves: consider iron availability, while checking other causes.
RULE 02
What happened to the veins?
- Leaf and veins fade together: consistent with nitrogen shortage.
- Green veins with yellow tissue: compare leaf age to distinguish magnesium from iron patterns.
OLDER LEAVES
N · MOBILE NUTRIENT
Nitrogen deficiency
A broadly pale or yellow older leaf, including the veins.
OLDER LEAVES
Mg · MOBILE NUTRIENT
Magnesium deficiency
Yellowing between veins that remain green, starting on mature leaves.
NEWEST LEAVES
Fe · LOW MOBILITY
Iron deficiency
Young leaves turn yellow between green veins; severe cases may become very pale.
These illustrations show common patterns, not a confirmed diagnosis. Symptoms can overlap, vary by crop or occur together.
SIDE BY SIDE
Nitrogen vs magnesium vs iron deficiency
| Clue | Nitrogen (N) | Magnesium (Mg) | Iron (Fe) |
|---|---|---|---|
| First leaves affected | Older, lower leaves | Older or mature leaves | Young, upper leaves |
| Typical yellowing | More uniform, veins included | Between greener veins | Between greener veins |
| Conditions to review | Nitrogen supply and leaching | Magnesium supply and potassium balance | Soil pH, lime and root conditions |
| Next step | Confirm N need; choose an appropriate N source | Confirm Mg need; select an Mg source | Address the cause of poor Fe availability |
01 · NITROGEN
Nitrogen deficiency: yellow older leaves
Signs to look for
- Yellowing usually begins on the oldest foliage.
- The leaf may fade more evenly, rather than leaving a strong green vein network.
- Growth may be weaker or slower when nitrogen supply is limiting.
What to check
- Recent fertilizer use and crop demand.
- Heavy rainfall or frequent watering that can leach nitrogen, particularly in sandy soil.
- Waterlogged or damaged roots that limit uptake.
GACIL option: Ammonium Sulphate NPK 21-0-0
Ammonium sulphate supplies nitrogen and sulphur. Consider it when nitrogen is needed and the source suits your crop and soil. Account for its acidifying effect over time; it is not a universal treatment for yellow leaves.
02 · MAGNESIUM
Magnesium deficiency: green veins on older leaves
Signs to look for
- Yellow areas develop between veins on older leaves.
- Veins remain greener than the surrounding tissue.
- More severe symptoms may include curling, brown spots or early leaf loss.
What to check
- Magnesium levels and the soil or potting-mix pH.
- Sandy soils and conditions that allow magnesium to leach.
- Excessive potassium application, which can contribute to magnesium uptake problems.
GACIL option: Magnesium Nitrate NPK 10-0-0
Magnesium nitrate supplies magnesium together with nitrogen. Check whether the crop needs both before choosing it. If nitrogen is already adequate, compare a suitable magnesium-only source such as GACIL Magnesium Sulphate, subject to the label and local recommendation.
03 · IRON
Iron deficiency: yellow new leaves
Signs to look for
- New leaves are affected more clearly than older foliage.
- The tissue between veins becomes yellow while the vein network stays green.
- In severe cases, new leaves can become almost white and growth can suffer.
What to check
- Alkaline or calcareous soil, where iron can be present but difficult to absorb.
- Poor drainage, prolonged wetness and root health.
- The needs of the crop: the pH at which iron problems develop varies between species.
Choose an iron treatment for the conditions
A confirmed iron problem may require an appropriate iron source, pH management or drainage correction. The choice of iron compound or chelate matters in alkaline soil. A multi-micronutrient mixture is an option only when its declared iron content and labelled use match the need.
Explore GACIL Multi Micronutrient Liquid or GACIL Multi Micronutrient Powder. Check the current composition and instructions rather than assuming every mixture treats every case of iron chlorosis.
BEFORE YOU APPLY
A practical checklist for yellow leaves
- Check the roots and water first. Correct persistent waterlogging, poor drainage or an unsuitable watering schedule.
- Look for pests, disease and ageing. Yellowing is not always caused by fertilizer shortage.
- Use crop-specific evidence. Review pH, a suitable soil test and tissue analysis where appropriate, especially if the pattern is unclear or widespread.
- Use the actual label. Match the rate, dilution, timing and application method to the selected product and crop. Liquid and powder doses are not interchangeable.
- Monitor new growth. Record the treatment and reassess the plant before adding more fertilizer.
Foliar spray: use the stated concentration
Apply only when the label permits foliar use. Follow its weather, mixing and crop-stage instructions; avoid spraying heat-stressed plants. Check compatibility before tank mixing and test a small area when advised. A dose suitable for one crop or formulation may damage another.
DIRECT STORE LINKS
Explore GACIL fertilizer options
Click a product photo, title or button to open its store page. Choose by the confirmed nutrient requirement, not leaf colour alone.
NITROGEN + SULPHUR
GACIL® Ammonium Sulphate
Review the nutrient details, available weights and directions.
MAGNESIUM + NITROGEN
GACIL® Magnesium Nitrate
Compare this source when magnesium and nitrogen are needed.
LIQUID FORMULATION
GACIL® Multi Micronutrient Liquid
Check the declared trace elements and crop instructions.
POWDER FORMULATION
GACIL® Multi Micronutrient Powder
Review the powder composition and labelled application rate.
QUICK ANSWERS
Frequently asked questions
Will yellow leaves turn green again?
Recovery depends on the cause, crop and extent of damage. Some chlorotic tissue can regain colour after the underlying problem is corrected; badly damaged leaves may not recover. Watch new growth rather than expecting a fixed number of days.
Can nitrogen, magnesium and iron problems occur together?
Yes. Several nutrient or root-zone problems can overlap. A mixed pattern is a reason to review tests, irrigation and soil conditions instead of automatically applying several fertilizers.
Are yellow leaves always a nutrient deficiency?
No. Watering problems, root injury, pests, disease, unsuitable light and normal leaf ageing can also cause yellowing. Examine the whole plant and its growing conditions.
How much fertilizer should I use?
Use the current product label and a recommendation suitable for your crop, soil and application method. Measure carefully; do not transfer a liquid dose to a powder or use the same foliar concentration for every plant.
