Drought usually means midday wilting and dry soil at twenty to thirty centimetres. A deficiency shows a pattern on old or young leaves and in the veins. Dig first, fertilise second.
In the summers of Isfahan, Yazd and Kerman, a tree turns yellow or wilts, and the first response is usually a foliar fertiliser or an extra watering. Sometimes both are needed; very often one of them does harm. Fertiliser burns a thirsty tree, and too much water on a tree suffering iron chlorosis makes the lime and the lack of oxygen worse. The diagnosis is read from three places: which leaves are affected — old or young — what colour the veins are, and whether the soil at twenty to thirty centimetres is genuinely moist. On a visit, before opening the fertiliser, Farin Kesht Taban puts a spade in. That simple habit halves the cost of testing and spraying.
Old leaf or young leaf: mobile or immobile element
Mobile elements such as nitrogen, potassium and magnesium move from old leaves to young ones. Their deficiency shows first on the lower, older leaves: uniform yellowing for nitrogen, marginal scorch for potassium, interveinal yellowing of the old leaf for magnesium. Immobile elements such as iron, zinc, manganese, calcium and boron get stuck in new tissue. Their deficiency appears at the shoot tips and on young leaves: iron chlorosis with green veins on a fresh leaf, little leaf for zinc, deformity for boron. Drought disturbs this logic because it puts the whole crown under pressure: leaves of any age may fold, dull over, or wilt at midday and recover a little in the evening. If only the upper crown is yellow while the lower stays green, think about an immobile element or root damage on that side, not necessarily about drought across the whole orchard.
- Yellow young leaves with green veins: take iron seriously; first check moisture and lime.
- Yellowing of old leaves from the bottom of the crown: nitrogen, or natural senescence after a crop; separate the two with a leaf test.
- Scorched margins on old leaves: potassium, or salinity at the wet edge of the drip; a spade and the irrigation map are needed.
- Little leaf and short internodes on the current year's shoots: confirm zinc with a leaf test.
- Midday wilting and folded leaves at every age: drought or damaged roots first, not a complete fertiliser.
Read the veins, then dig
Interveinal chlorosis on a young leaf is almost always close to iron or manganese; separating them precisely takes a leaf test, not a colour from memory. Uniform yellowing of an old leaf is closer to nitrogen. Red or purple veins on some cultivars can be phosphorus, cold or simply the cultivar. Do not fertilise for any of these patterns while the soil at spade depth is dry and powdery. Put the spade in in the canopy shade, not at the foot of the trunk and not in the dry middle of the row. In Iran's sun the top ten centimetres always lie: the surface is dry with moisture beneath, or the surface is wet after a shallow watering with thirst below. Twenty to thirty centimetres is where the active roots of most fruit trees and many urban trees work. If it is dry there, the problem is water. If it is wet and smells foul there, the problem is drainage. If it is evenly moist there and the young leaves are still yellow, think about elements and pH.
Midday wilting against persistent chlorosis
A drought-stressed tree wilts at midday, folds or rolls its leaves, and recovers a little in the evening as it cools. If it stays wilted at night, the roots or the vascular tissue are damaged, or the drought has gone very far. A nutrient deficiency on its own usually does not cause midday wilting; the leaf is yellow or small but keeps its turgor, unless the deficiency comes with salinity or heat. The common Iranian combination is exactly this: insufficient irrigation plus lime. The tree is both wilting and chlorotic. Here the order of treatment matters: correct the moisture first, then the foliar spray or the chelate. Spraying iron on a wilting leaf causes scorch, and the grower concludes the fertiliser was counterfeit.
If you have not put a spade in, you still do not know whether the tree is hungry or thirsty. Fertiliser is the most expensive way to guess.
- Look at the same tree at midday and in the evening: does the leaf recover or not?
- Describe young leaves and old leaves separately and photograph the veins.
- Dig in the canopy shade to twenty to thirty centimetres and record moisture and smell.
- If the soil is dry, water and wait three to seven days; if it is wet and the tree is yellow, think about drainage and iron.
- Take the leaf test when there is no acute water stress, so the figures are not misleading.
A few diagnostic mistakes recur in the orchards Farkesht visits. One is taking a leaf test at the peak of thirst; element figures in a wilting leaf are misleading. Second, seeing iron chlorosis and immediately flooding the tree in calcareous clay; anaerobic roots take up iron even worse. Third, scorching the leaf margins after a saline fertiliser and calling it potassium deficiency. Fourth, treating yellowing from mite as the same as yellowing from nitrogen. Look at the underside of the leaf. If several trees in one row wilt at midday at the same time, look first at the irrigation line and dripper blockage; a nutrient deficiency usually differs tree by tree and by cultivar, not exactly simultaneously along a whole row. That distinction separates the fertiliser store from the filter repair.
The diagnosis in summary: recognise drought from midday wilting, leaves of every age and dry soil at root depth. Recognise a deficiency from the pattern of old versus young leaves and from the colour of the veins. In Iran's calcareous orchards the two usually arrive together; the order of work is water and root oxygen first, elements second. For the orchards it monitors, Farkesht gives the workers a simple sheet — midday / evening / spade / young leaf / old leaf — so the sprayer tank is not filled out of habit. If the pattern remains after the moisture has been corrected, then a test and a fertiliser make sense. Do not feed a thirsty tree; do not flood an underfed one.
