Chlorosis and necrosis of young leaves are early symptoms of manganese deficiency. Tomato plants growing in calcareous soils in Florida showed retarded growth, failure to blossom, chlorosis, and a necrotic spotting of the younger leaves until manganese was supplied. The gray speck disease of oats is due to too little manganese. The first seedling leaves of the oat plant are of a normal green; later leaves are faintly yellow and develop necrotic spots. "Pahala blight" of sugarcane arises from too little manganese. Snap beans show a chlorosis of the young leaves; each new leaf shows more chlorosis, and affected plants finally die. Young leaves of an ailing tobacco plant lose color in even the smallest veins; the contrast between the green and yellow places gives a checkered effect to the leaf. chlorotic leaves develop small lifeless spots, which may enlarge and fall out. The Spots are distributed over the leaf not only at the tip and margin, as with potassium deficiency. The acidity or alkalinity of the soil on which the Plant grows appears to dominate manganese absorption, as most instances Of deficiency of manganese have been reported on neutral or alkaline soils.

The effect of molybdenum deficiency was first mentioned as a cause of the whiptail disease of cauliflower in New Zealand and Australia. The disease restricts the development of the leaf lamina, so that sometimes the midribs are left bare. In extreme cases the growing point dies. The effects of a shortage of molybdenum on tobacco and tomatoes has been reported for plants grown in nutrient solutions. The tomato plant shows a mottling of the lower leaves, followed by necrosis and crinkling. The fruit set is poor because most of the blossoms shed. Tobacco shows much the same symptoms when molybdenum is deficient; the shedding of flower buds leads to a reduction in amount of seed. Various crops, particularly legumes, have responded favorably to the addition of molybdenum on serpentine and ironstone soils in some areas.

Shortage of nitrogen, perhaps the most common of the deficiencies, shows up at any time from the seedling stage to maturity. First the plant loses its normal green color. The growth rate slows down. Then lemon, orange, red, or purple tints develop and the older leaves dry or drop. Leaves that develop later when nitrogen is transferred to them from the older leaves are small; the production of fruit or seed is correspondingly reduced. The growth of nitrogen-deficient plants is sparse, spindly, and erect. The roots may be long and little branched; the twigs of trees are short and small. Small grains show a marked reduction in number of tillers and consequently yield poorly. Not all effects of nitrogen deficiency are bad, however. The growth of broadleaved plants, such as tobacco, can be regulated by withholding nitrogen to produce leaf of a certain type, such as the bright lemon-colored leaf known as the flue-cured type. Fruit trees on nitrogen-deficient soil may produce highly colored fruits that store well.

Shortages of phosphorus lower plant growth markedly. The symptoms are not always clearly defined. Usually the leaves are small and erect, the lateral buds are few, and the roots may be sparsely branched. But most of the effects of phosphorus deficiency apparently are more general. The leaves usually are dark green, but in later stages or in extreme cases they may be dull green and may show purplish tints. Sometimes necrosis is evident. When the older leaves dry up or shed they are dark brown to almost black. The cereals often show purpling on older leaves. Tobacco leaves are a dark gray green and maturity is delayed. Production of fruit and seed is reduced and slow.

chlorosis, commonly beginning on the older leaves at their tips and margins, is typical of potassium deficiency. Necrosis follows, first as small areas that gradually enlarge and merge. The dead areas may fall out so the leaves get a ragged appearance. Grasses, when potassium is deficient, show a yellowish streaking which, on older leaves, may develop into scorching. The stalks on such plants are short, roots are poor, and the ears are poorly filled at the tip. The tobacco plant becomes bluish green, mottled, and chlorotic. Generally the lower leaves show the first symptoms, but if the shortage operates during later growth stages of the plant, when growth is rapid, the upper leaves may show the first symptoms. Mottling is followed quickly by necrotic spotting at the leaf tips and margins between the veins. Tomato and the potato plants show much the same symptoms as tobacco. Tomato fruits fail to ripen evenly; often greenish-yellow patches are intermingled with the red of the red-fruited varieties. Cotton and the sweetpotato develop chlorosis and necrosis of the older leaves and some leaf shedding. Cotton rust is associated with potassium deficiency. Foliage of deciduous fruit trees becomes bluish green; intervein chlorosis, necrosis, and marginal scorch occur on older leaves; extreme cases involve dieback of shoots and branches and fruits of poor quality. Citrus fruits display small leaves, fluting or tucking along the midrib, small and poor fruit, and die-back in serious disorders.

The effects of sulfur deficiency on plant growth generally resemble those caused by shortage of nitrogen. The younger leaves display a pronounced yellowing with little or no drying of older leaves. While nitrogen shortage is accentuated and sometimes brought about by excessive rainfall, sulfur shortage is often more apparent during dry periods and in dry areas, since sulfur dioxide, a common air contaminant, is brought down by rainfall. Grasses lose their normal green color when sulfur is withheld. Leaves of legumes become yellow and develop brown spots; the plants are less succulent and have thin stems. The tobacco plant first shows light-green leaves; veins and the tissue between the veins lose their green color when sulfur is deficient. Much the same symptoms have been reported for the tomato. The tobacco plant recovers quickly from sulfur deficiency in times of adequate rainfall. Citrus trees show a marked yellowing of the younger leaves in the early stages of the deficiency. Some dieback of the twigs may occur later. A disease known as tea yellows is caused by sulfur deficiency. The initial stages of sulfur deficiency generally are marked by a yellowing of the younger leaves. When the condition becomes acute and lasting, the older leaves may turn yellow. Leaves of citrus and the tea bush may die back.