Little leaf and delayed bud break in almond and peach are zinc deficiency, not iron chlorosis. In the calcareous soils of Najafabad and Saman zinc is fixed; do not overdose the winter foliar spray.
In the almond orchards of Najafabad and Saman, the peach and nectarine of Semirom, and the apricot of Khorasan and Azerbaijan, every spring a number of trees wake later than the rest. The leaves at the shoot tips stay small, the internodes compress, and the tip of the branch takes on the shape of a brush. The grower sometimes blames a late frost, sometimes general weakness, and very often an iron deficiency. But this is the classic pattern of zinc deficiency: small leaves, short internodes, rosetted shoot tips and delayed bud break. Zinc has a role in building growth hormone and in cell division at the apical meristem; when it is short in new tissue, the tree becomes impoverished from the tip, not from the old leaves. If that picture is confused with iron chlorosis, a season of iron fertiliser is spent with no effect and the buds still open late.
Yellow young leaves are iron; little leaf and rosetting are zinc
Iron chlorosis in Iran's calcareous soils shows on the young leaves: a yellow blade, green veins, and leaf size usually close to normal. Zinc deficiency has a different face. The new leaf stays small and sometimes narrow or cupped, the internodes shorten, and the buds open late or incompletely. The colour may be pale green, but the dominant symptom is size and branch arrangement, not interveinal yellowing alone. Both deficiencies occur together in alkaline soil, especially in Najafabad, Saman and the calcareous plots of Khorasan. Treating one does not fix the other. Foliar iron greens the young leaves temporarily but does not reverse the rosetting and the delayed bud break. Conversely, a heavy zinc spray applied without need causes scorch and also disrupts iron uptake; that is, after a high dose the iron chlorosis may become more obvious. Diagnosis starts from the pattern in the crown and finishes with a leaf analysis at the standard time.
Almond on the calcareous soils west of Isfahan and around Saman is very sensitive to zinc deficiency, and its delayed awakening is very often mistaken for spring frost. Frost damages the flowers; it does not shorten internodes or cup the leaves. The peach and nectarine of Semirom and similar orchards spend their zinc reserve on the fruit in a heavy year and build weaker shoots the following year. The apricot of Khorasan and Azerbaijan is sometimes confused with a viral leaf curl. Zinc deficiency usually appears on the current season's shoots and is spread relatively symmetrically through the crown; some diseases take one side of the tree or a few scattered branches. The leaf analysis must be taken from mid-shoot leaves of the current year's growth in the middle of the growing season. A sample of severely undersized tip leaves gives an unrealistically low figure and pushes the grower into overapplication.
Zinc is in the soil; at high pH it is not in the soil solution
In many Iranian orchards, zinc is not short in total quantity. A pH usually between 7.6 and 8.6 in the calcareous plots of the plateau turns the element into an insoluble form. Active lime coats the surface of the particles, and excess phosphorus — which comes from heavy superphosphate applications in many stone-fruit orchards — intensifies the fixation. The roots of almond and peach become active early in spring, and the zinc requirement for shoot and flower growth is high in exactly those weeks. If the soil solution is empty, the symptom is carved into that year's shoot and summer fertiliser arrives too late for the bud. Irregular irrigation, a surface crust and low organic matter in the sandy plots of Saman and around Najafabad increase the roots' contact with the fixed layer. Spreading zinc sulphate over a crusted surface, without placing it in the band of canopy shade and without enough water, repeats that same fixation above pH 8.
Late-winter foliar spraying; soil application for the reserve
For an acute deficiency and to improve bud break in the same spring, a zinc foliar spray in late winter or at bud swell is the main tool. Zinc sulphate and zinc chelate can both be used; the choice depends on the cultivar's sensitivity, the daytime temperature at spraying, and that orchard's history of scorch. The effect of foliar spraying does not stay in the soil reserve. If the fixation continues, it has to be repeated the following year. Soil application means something when the element reaches the band of active roots. Above pH 8, a surface spread of sulphate loses much of its effect. Placement in the canopy shade, going in with rotted organic matter, and, in a drip orchard, injecting chelate during irrigation all improve the chances of mobility. Do not mix zinc chelate with high phosphorus in the same tank. EDTA and DTPA have a use in foliar sprays; do not expect long-term stability from them in a strongly alkaline soil.
- Dormant or bud-swell spraying: the response for little leaf and delayed bud break in the same spring.
- Spraying after fruit set: helps next year's reserve; keep the dose low.
- Soil application in autumn or early spring in the root band: correcting the reserve, not a rescue for that week.
- Do not repeat heavy phosphorus in the same band where you apply zinc.
A high dose does not correct the deficiency faster
The temptation on seeing a rosetted shoot tip is to double or triple the dose. Excess zinc burns the leaf, dries the bud and disturbs the uptake of iron and manganese. In peach and nectarine, the skin is thinner and the scorch shows sooner. Spray in cool weather with an even coverage, and do not repeat back to back in the same week. If you sprayed last year and this year the symptom is mild, measure the leaf first; repeating a high dose is unnecessary. A once-and-forget programme is not durable in calcareous soil, but monthly zinc spraying also exhausts the tree. Leaf monitoring every two years is the minimum. Severe pruning of peach and nectarine builds dense shoots; if zinc is short, those same shoots rosette. Do not put that down to a deficiency until you have seen the leaf figure.
If a peach wakes late every year and the leaves at the shoot tips stay like small spoons, measure the zinc first. A complete fertiliser without a number does not change this pattern.
- Separate little leaf and delayed bud break from frost, virus and iron chlorosis.
- Leaf analysis at the standard time; sample from mid-shoot leaves of the current year's growth.
- For the same spring: a zinc sulphate or chelate spray in late winter or at bud swell.
- For the reserve: soil application in the root band, with an eye on pH and phosphorus.
- Do not raise the dose; scorch and interference with iron cost more than the deficiency itself.
Zinc deficiency in almond, peach, nectarine and apricot is among the most common hidden deficiencies of Iran's calcareous orchards. The symptom starts at the bud and the new leaf because zinc is poorly mobile within the plant. Fixation at high pH is the main cause, not necessarily an absolute poverty of the element. Foliar spraying manages the deficiency for that season; correct soil application reduces the annual repetition. Overdoing it damages as much as ignoring it. In its stone-fruit programme, Farin Kesht Taban treats zinc separately from iron and ties the timing of the foliar spray to bud swell.
