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close this bookTraditional Field Crops (Peace Corps, 1981, 283 p.)
close this folderAppendices
close this folderAppendix G - Hunger signs in the reference crops
View the documentNitrogen
View the documentPhosphorus
View the documentPotassium
View the documentCalcium
View the documentMagnesium
View the documentSulfur
View the documentZinc
View the documentIron
View the documentManganese
View the documentBoron

Nitrogen

Maize, Sorghum, Millet

Young plants are stunted and spindly with yellowish-green leaves. In older plants, the tips of the lower leaves first show yellowing which progresses up the mid-rib in a "V" shaped pattern, while the leaf margins remain green. In some cases, a general yellowing of the lower leaves occurs. In severe cases, the lower leaves soon turn brown and die from the tips down. (This "firing" can also be caused by drought which prevents N uptake.) Maize ears are mall and pinched at the tips.

Legumes

The lower leaves begin to turn light green and then yellow with the symptoms progressing gradually upward. Plant growth is stunted.

Phosphorus

Maize, Sorghum, Millet

Hunger signs are most likely during early growth. Mild shortages usually cause stunting without clear leaf symptoms. More severe shortages cause a purplish color starting at the tips of the lower (older) leaves which may begin to turn brown and die. Some varieties of maize and sorghum do not show a purplish color but rather a bronze coloration of the same pattern. Disregard purple stems.

In maize and sorghum, symptoms usually disappear once the plants reach 40-45 cm, but yields will be severely lowered. Maize ears from Pdeficient plants are somewhat twisted, have irregular seed rows, and seedless tips.

Legumes

Phosphorus hunger signs often are not well defined. Plants lack vigor and have few side branches. Upper leaves become dark green, but remain small. Flowering and maturation are retarded.

Potassium

Maize, Sorghum, Millet

The three crops rarely show symptoms the first several weeks of growth. The margins of the lower leaves turn yellow and die, starting at the tip. Potassium-deficient plants have short internodes and weak stalks. Maize stalks sliced lengthwise often reveal nodes that are a darkish brown. Maize ears from potassium-deficient plants are often small and may have pointed, poorly seeded tips.

Legumes

Potassium deficiency is seldom seen in beans, but can occur in highly infertile soils or those high in calcium and magnesium. Symptoms are yellowing and death of leaf tips and margins, beginning on the lower leaves and gradually moving upwards.

Calcium

Beans

Calcium deficiency in beans is uncommon, but most likely to occur in combination with aluminum toxicity in very acid soils. Leaves stay green with a slight yellowing at the margins and tips. Leaves may pucker and curl downwards. Peanuts

Light green plants with a high percentage of "pops" (unfilled pods) show symptoms of calcium deficiency.

Magnesium

Maize, Sorghum, Millet

A general yellowing of the lower leaves is the first sign. Eventually, the area between the veins turns light yellow to almost white while the veins remain fairly green. As the deficiency progresses, the leaves turn reddish-purple along their edges and tips, starting at the lower leaves and working upward. Beans

Most likely in acid soils or those high in Ca and K. Yellowing between the veins appears first on older leaves and then moves upward. Leaf tips show the first effects.

Sulfur

Where to suspect: Sulfur deficiencies may be suspected where there are volcanic or acid, sandy soils, and where low S fertilizers have been used for several years.

Maize, Sorghum, Millet

These crops have relatively low S needs. Stunted growth, delayed maturity, and a general yellowing of the leaves (as distinguished from N deficiency) are the main signs. Sometimes, the veins may stay green which may be mistaken for zinc or iron deficiency. However, iron and zinc hunger are more likely in basic or only slightly acid soils. Beans

Upper leaves become uniformly yellow.

Zinc

Zinc deficiencies occur where soil pH is above 6.8 and high rates of P are used, especially if placed in a band or hole near the seeds.

Maize

Maize shows the most clear-cut zinc hunger signs of all crops. If severe, symptoms appear within two weeks of emergence. A broad band of bleached tissue on each side of the midribs of the upper leaves, mainly on the lower part of the leaves, is typical. The mid-rib and leaf margin stay green, and the plants are stunted. Mild shortages may cause a striping between the veins similar to manganese or iron deficiency. However, in Fe and Mn shortages, this interveinal striping runs the full length of the leaf.

Sorghum

Similar to maize, but less interveinal striping, and the white band is more defined.

Legumes

Interveinal yellowing of the upper leaves.

Iron

Iron deficiencies can be suspected where soil pH is above 6.8.

Maize, Sorghum, Millet

Sorghum is much more prone to iron deficiency than maize. All three crops show an interveinal yellowing that extends the full length of the leaves and occurs mainly on the upper leaves.

Legumes

Interveinal yellowing of the upper leaves occurs. They eventually may turn uniformly yellow.

Manganese

Where to suspect: Manganese deficiencies are uncommon in maize, millet, or sorghum. It occurs in soils which have a pH of 6.8 or above and in sandy or heavily leached soils.

Peanuts

Yellowing between the veins of the upper leaves which eventually turn uniformly yellow and then bronze is a symptom.

Beans

Plants are stunted. Upper leaves become yellow between the small veins and eventually take on a bronzed appearance.

Manganese toxicity occurs on very acid soils and is accentuated by poor drainage. Beans are very susceptible. The upper leaves show an interveinal yellowing. Easily confused with Zn or Mg deficiency, but Zn deficiency is very uncommon in highly acid soils.

Boron

Where to suspect: Boron deficiencies can be suspected in acid, sandy soils or high pH soils. Beans and peanuts are the most susceptible of the reference crops.

Peanuts

Foliage may be normal, but kernels often have a hollowed out, brownish area in the meat. This is usually referred to as "internal damage".

Beans

Thick stems and leaves with yellow and dead spots. If less severe, leaves are puckered and curl downward. Easily confused with leafhopper or virus attack. In very severe cases, plants stay stunted and may die shortly after emergence. Boron toxicity can be caused by applying a fertilizer containing boron too close to the seed row or by applying B non-uniformly. Symptoms are yellowing and dying along the leaf margins of the plants shortly after emergence.