In this section we will try to inform about the mineral components that should be part of the fruit tree fertilizer, and from this, try to know the nutritional deficiencies from a visual inspection.
ESSENTIAL CONDITIONS FOR THE NUTRITION OF FRUIT TREES. MINERAL DEFICIENCIES IN FRUIT TREES
In plants we can find more than 100 elements, but only some of them are considered essential. These minerals are classified as follows.
Macroelements: 99% (C: 40-50%, O: 42-44%, H: 6-7%)
Primary macroelements: N, P, K.
Secondary macroelements: Ca, Mg, S
Essential trace elements: Fe, Mn, B, Zn, Cu, Mo, Cl.
FUNCTIONS OF NUTRITIONAL ELEMENTS
IMPORTANCE OF BORON
This element participates in the development of the pollen tube and the flowers.
In fruit trees, the deficiency is exceptional, and may be due to the high content of its antagonist, Ca.
IMPORTANCE OF CALCIUM
Calcium is abundant in the leaves and increases with age. It is also present in the bark. It is a deficiency that occurs only in very acid soils, so the corresponding solution is to reduce that acidity with limes (CaO or quicklime, slaked lime, gypsum, etc.).
IMPORTANCE OF MAGNESIUM
It is an important component of chlorophyll and in the fertilization of fruit trees, and it is found in developing organs such as flower buds in formation. It contributes to the formation of proteins and has great mobility in the plant.
IMPORTANCE OF ZINC
It is associated with the synthesis of indoleacetic acid (IAA). The lack of this element is solved with applications of zinc sulfate in irrigation and in foliar applications.
IMPORTANCE OF COPPER
Its role is considered similar to that of the previous element ZINC.
IMPORTANCE OF SULFUR
Sulfur deficiency is usually very rare, since when fertilizing fruit trees, indirect amendments of this mineral are already carried out. It is a key compound in the regulation of metabolic pathways and in the activation of organic acids.
IMPORTANCE OF PHOSPHORUS
Its deficiency produces delays in growth, defective fertilization, abnormal movements of reserves, delays in maturation, etc.
IMPORTANCE OF POTASSIUM
It is the element with the highest mobility and solubility in tissues. Regulates water absorption, perspiration, carbohydrate synthesis, etc. Its deficiency restricts the development of shoots and delays the fall of the leaf in autumn.
DISCOVERING THE GAPS
Sometimes the deficiencies can be seen with the naked eye, others require laboratory studies and foliar analysis. Here we are going to comment on the main deficiencies that may appear in crops.
Changes appear on old sheets. Leaves are lighter, pale green in color, turning yellow, including the veins. The yellowing of the leaves, although it begins with the old leaves, reaches the whole plant. One way to distinguish iron deficiency or iron chlorosis is to observe that in this case, chlorosis begins with the youngest leaves, as opposed to nitrogen deficiency.
Solution : application of nitrogen fertilizers (ammonium nitrate, calcium nitrate, potassium nitrate, etc.)
It is involved in the exchange of N in plant tissues. The presence of this deficiency is rare, and generally presents a chlorosis that begins in the adult leaves. This chlorosis can appear only in the nerves of the leaves or appear necrosis at the edges (with deformations in the form of a roll)
Solution: in general, increase the pH (add basicity to the soil) to unblock the molybdenum.
The first signs of potassium deficiency are seen on old leaves. These present the tips and edges of the leaves yellowing to dry over time. In some cases, redness of the young leaves is observed. From here the growth of the crop, fruiting and flowering are affected.
Solution : use of fertilizers with potassium content (ClK, potassium sulfate, potassium nitrate, monopotassium phosphate) in irrigations and foliar application of 2% potassium sulfate.
The deficiency of this mineral appears in its beginnings in the lower leaves, which correspond to the oldest. The coloring of the leaves begins with a dark green hue that turns reddish until dry.
Over time, the size of the leaves decreases and the shoots and stems become thinner.
Solution : fertilizer with phosphoric base inside the soil (from 10 cm) to facilitate access to roots, since this element has little mobility.
Iron deficiency (iron chlorosis) is one of the best known. The first manifestation begins in the young leaves, with a yellowish coloration of the leaf except the veins. The progress of this deficiency ends up yellowing the leaf completely and spreads to the adult leaves. It can be distinguished from other chlorosis because the culture presents this anomaly in a non-uniform way.
Solution: the origin of this deficiency may be largely due to a high soil pH. A temporary solution to improve the crop is the application of iron chelate fertilizers, but if the soil is basic the problem will arise again, so it is convenient to acidify the soil (acid peat, citric acid, iron chelates, etc. )
Manganese deficiency is manifested in the leaves and the most notable symptom is chlorosis since this element plays a fundamental role in photosynthesis. It starts on the young leaves. When the deficiency is severe, the new leaves emerge with freckles and striations all along. Although the striatum occurs between the ribs, it differs from that caused by the lack of Fe due to its irregularity and the appearance of freckles.
Solution: The appearance of this deficiency is mainly due to limestone soils (high pH) since the solubility and absorption of this mineral is decreased. It can also appear in soils with coarse texture, such as sandy ones. Manganese chelates are usually applied on irrigation or sprayed on the leaves, in addition to other commercial fertilizers such as manganese sulfate, manganese chloride, manganese nitrate, Agroxylate Mn®, etc.
Zinc deficiency is manifested in young leaves, producing a chlorotic mottling. In citrus, irregular bands appear along the main veins, on the bottom of the leaf that turns whitish yellow.
Shoot growth stops and the plant takes on a rosette-shaped appearance. In the final stage of the disease the branches necrotize and die from the tips. The severely affected plants stop producing fruits, or these are small and very bitter to the taste.
Solution: The appearance of this deficiency is conditioned by the cultivation in limestone soils, deficient in organic matter or very eroded, very cultivated soils. When the beginning of this deficiency is denoted, it is acted with Zinc chelates or Zinc sulfate.
The sulfur deficiency , although rare cases are the following features. The plant suffers from generalized chlorosis that includes the vascular bundles. It usually occurs in young leaves at the beginning, since sulfur has little mobility.
In general, they have a reduced growth, weakening the stems and becoming more brittle. Defoliation may occur in some crops. As the deficiency of this mineral evolves, the leaves tend to wrinkle.