Mineral nutrition

Primary symptoms

Yield can often be reduced 10-30% by deficiencies of major nutrients before any clear symptoms of deficiency are observed in the field. Stunting or color changes are typical symptoms of deficiency. Field observations, calculations and soil analysis can indicate nutrient deficiencies.

Confirm the problem by checking the tables below.


The maize crop needs certain mineral elements in adequate quantities for good growth. These nutrients are generally supplied from the soil and from added fertilizers. Although the maize plant uses 13 different nutrients, only three are required in relatively large quantities: nitrogen, phosphorus, and potassium. These are the nutrients which most frequently limit maize production, but sulfur and some micronutrients such as zinc and magnesium may be important constraints in some areas.

Yield can often be reduced 10-30% by deficiencies of major nutrients before any clear symptoms of deficiency are observed in the field. Even if you don't see symptoms, it is a good idea to calculate a nitrogen balance and analyze soil P levels.

Causes of nutrient deficiencyAdditional evidence required
Not enough fertilizer (NPK) was applied. Ask farmer how much fertilizer was applied.
Fertilizer applied is lost to leaching, runoff, or volatilization. Ask farmers about fertilizer source and placement, and rainfall events after application.
Fertilizer is applied when the crop cannot use it well, or when the crop is already stunted due to factors such as inadequate weed control. Ask when fertilizer was applied, and about the crop condition when application was made.
Waterlogging results in N deficiency. Check for symptoms of waterlogging (See waterlogging). Ask farmer about rainfall.
There is excessive competition with weeds or intercrops for nutrients. Check for presence of weeds or intercrop.
Soil pH makes certain nutrients unavailable. Test soil pH. If 8, deficiencies of Zn, Fe, and Cu are common. See acid and alkaline soils.
The soil contains low amounts of certain micronutrients. Soil test are difficult to interpret. Apply foliar solution or soil amendments to a small test plot and look for a change in symptoms.

Symptom summary

SymptomLikely deficiencyComment
Paling and yellowing of leaves Nitrogen or sulfur N is more apparent on older leaves; Sulfur on the whole plant
Reddish-purple Phosphorus Purpling can be due to cold
Yellowing and dying along leaf edge Nitrogen or potassium Nitrogen forms an inverted V starting from the leaf tip. Drought causes similar symptoms.
Pale chlorotic stripes on upper leaves Iron or (rarely) copper Chlorosis may be induced by high soil pH
Broad whitish bands running along center of new leaves Zinc  
Yellow striping (chlorosis) on lower leaves Magnesium  

Is mineral nutrition a problem?

Evidence: observations.

Walk through the field at different growth stages. If you find the leaf symptoms mentioned below, you can assume that the deficiency is probably important enough to cause some yield reduction. Recall that some diseases can cause symptoms similar to nutrient deficiency. If the cause is nutrient deficiency, symptoms will tend to occur in large areas of the field. If you see the symptoms on isolated plants, they are more likely the result of disease.

  1. Before the V6 stage, pale yellow plants with small leaves and slow growth indicate N deficiency or, less commonly, S deficiency. Plants with reddish-purple color along the edges of the leaves can indicate P deficiency (this symptom is accentuated by cool weather).
  2. During the period of rapid elongation, lower leaves with yellowing beginning at the tip and moving along the middle of the leaf in a 'v' shape indicates N deficiency. If the yellowing moves along the edges, the problem may be K shortage. At this stage other nutrient deficiency symptoms can also appear, such as pale, chlorotic stripes on the leaves. If this happens on the upper leaves, it can be due to a lack of iron or, in rare cases, copper. Broad whitish bands running along the center of new leaves or in the zone of elongation at the base of leaves may reveal zinc shortage. Yellow striping (chlorosis) on lower leaves may mean magnesium deficiency.
  3. What was the previous crop? You can often tell by looking at the residue in the field, or you can ask the farmer. If maize follows a heavily fertilized cash crop, deficiencies of major nutrients are less likely.

Compare the heights of plants on the edge of the field with those having full competition. The plants with less competition will tend to be taller than the plants which are completely surrounded if drought or nutrient stress has occurred.

Evidence: calculations.

Even if you do not see clear symptoms of nitrogen deficiency in the field, you are not justified in saying that no response to N fertilizer can be expected. Ask the farmer how much N fertilizer he applies, and how much maize he harvests. You can now make some calculations to predict whether nitrogen is limiting.

First calculate the amount of N which is being supplied to the crop by sources other than the fertilizer applied by the farmer. The simplest way to do this is by calculating the N content of an unfertilized crop growing in a similar soil and environment when water is not limiting. Try to find a farmer who did not apply N either to his maize or to the previous crops in that field, and ask what yield he obtained when drought stress was not important. Assume that about 25 kg N/ha are required to produce each ton of grain.

N supplying capacity of soil/ha/season = tons of grain produced/ha x 25

>This N will come from several sources. One important source is soil organic matter, which will be abundant in a recently cleared field or after a long fallow, but which will tend to decline with continuous cropping (see Table 6 below). You can improve your estimate of the N supplying capacity of the soil in your region by finding out maize yields of unfertilized fields and relating them to their cropping histories. The other inputs of N will be from rain, dust, and non-symbiotic N fixation.

N from soil + (fertilizer N applied x 0.4)

Now add to this amount the N from the fertilizer applied by the farmer. The efficiency of recovery of applied fertilizer will vary, but you can assume for this calculation that about 40% of the fertilizer N applied is available to the plant. The total input of N will be:

Is this amount as large as that removed by a crop which yields the potential for the area? (Assume that, for a yield level near 4 tons, about 15 kg N/ha are removed for each ton of grain, and add to this another 10 kg N/ha per ton of grain if the stover is removed from the field.) If not, N supply may be limiting.

Evidence: soil analysis.

You can use soil analyses to determine whether to expect a response to P or K fertilizer. For these tests to be really accurate, however, they must be calibrated for the soils in the region.

For P. The Bray I test can be used for acid soils. A value of

For K. The results should be expressed as milliequivalents of K 1100 g soil. Depending on the soil, the sufficiency values vary widely, but in general, a value of

Table 6. Approximate amounts of N supplied annually from soil organic matter in different environments.

EnvironmentHistorykg N / ha / yr
Lowland tropical forest Recently cleared 55
Cropped > 4 years 22
High rainfall tropical Savannah
(1,250 mm/yr)
Long fallow 15
Short or no fallow 5
Low rainfall tropical Savannah
(850 mm/yr)
Long fallow 4
Short or no fallow 2
Tropical highland forest Recently cleared 45

Possible solutions

  • Increase fertilizer rate.
  • Change fertilizer application method or timing so that less is lost.
  • Improve drainage.
  • Reduce weed competition.
  • Lime to increase soil pH.
  • Apply micronutrients.