How to help fruit trees overcome stress?

Every living being, even the plants we grow, feel best in optimal conditions, because when the plants are ‘happy and satisfied’ they give us the fruits we live on.

Any deviation from the optimum for the plant represents a smaller or larger stress that it has to deal with. Plants experience stress when they are grown in inadequate conditions (soil, moisture, sunlight…), if they are mechanically damaged (hail, cultivation…), exposed to drought, frost, chemical agents or attacked by plant diseases and pests.

Most often, several of these negative factors work together or one causes the appearance of the other. For example, if a plant has been exposed to a long-term effect of drought and lack of nutrients, it becomes susceptible to diseases. Unfortunately, despite the almost ideal climatic conditions that prevail in our country, we are often unable to provide the optimum for cultivated plants, or so we think.

Water is the basic element of life and the basic prerequisite for avoiding stress and ensuring high and stable yields. In fact, the most common cause of stress in fruit trees is lack of water. In our climatic conditions, the lack of water during the summer will usually not kill the plant, at least not an adult and healthy one, but it will cause a smaller crop and smaller fruits, as well as a weaker bud differentiation for the following year. This type of stress can be avoided by planting orchards close to available water, and alleviated by choosing species and varieties more tolerant to drought, whose fruits ripen earlier (for example, cherry and sour cherry grafted on magriva). Foliar feeding with nitrogen fertilizers with the addition of microelements during the dry period helps plants overcome stress.

Inadequate soil pH can often lead to stress due to the plant’s inability to absorb the necessary nutrients. A very low pH value in the majority of cultivated plants leads to a difficult uptake of some essential elements (Ca, Mg, P, Mo, B), and the reduced resistance of plants to diseases in a very acidic environment is precisely caused by the lack of calcium and the toxic effects of aluminum. That is why the acidity of the soil should be controlled more often (samples taken from the plant’s feeding zone) and, if necessary, intervene by introducing adequate amounts of lime fertilizer (if it is a question of low pH), or by destroying acidic fertilizers (potassium sulfate, elemental sulfur, UREA) if it is a question pH too high.

Unbalanced nutrition can often be the cause of fruit tree stress. A lack of nutrients, as well as an excess of certain mineral substances, can have negative consequences for the growth and fruiting of cultivated plants. The random throwing of large amounts of mineral fertilizers leads to the unnecessary accumulation of certain elements in the soil. A higher concentration of one element in the soil usually causes a lack of another in the plant tissue, which of course affects a number of disorders that occur in the plant. The most obvious phenomenon of unbalanced nutrition in orchards in our country is reflected in the excessive use of nitrogen fertilizers, which induce great lushness and lower fertility of fruit trees, as well as increased sensitivity of plants to certain diseases and pests. Properly dosed and complete nutrition of the plant is the basis for high and stable yields as well as increased resistance to diseases.

A common cause of stress in plants is improper use of plant protection products. The use of preparations outside of their proper purpose, combining preparations that are “not tolerated” as well as the use of high doses, often cause poisoning of plants. Plants need to be protected only when there is a justified reason for it and on the recommendation of an expert, while the recommendations of the manufacturer of chemical agents on dosage and the possibility of mixing with other protective agents and plant nutrients must be followed.

Excessive application of herbicides has a significant effect on reducing the resistance of fruit trees to diseases and drought, because it becomes more difficult to absorb water and nutrients (Mn, Zn, B), which disrupts the normal process of synthesis of substances essential for the functioning of the plant’s defense system. By growing grass mixtures in the middle row, in orchards that can be irrigated, we provide a friendly environment for the roots of cultivated plants, thus creating conditions for their better functioning and fruiting.

Source: B.Sc. Eng. Momir Nedić, PSSS Kruševac

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