Reasons for the need for fertilization

Walnuts are not pretentious and grow well both in deep permeable and nutrient-rich soils and in poorer ones. Their development in the same place for years depletes nutrients from the soil. They are also lost with the fruits and when the branches are pruned and the leaves fall. Every year, the walnut extracts 10 - 18 kg of nitrogen, 4 kg of phosphorus, and 20 kg of potassium from 1 acre. For their development, plants obtain most of their mineral nutrients from the water solution of the soil. When the tree is young, it acquires the necessary food reserves for bud development and growth from the stem and roots. More nutrients will be absorbed from the soil as the roots grow. The walnut needs balanced nutrition, according to the phase of development and the size of the yield. With a lack of mineral substances, they become sensitive to frost and diseases. We recommend the use of simple fertilizers (containing one element) obtained naturally without chemical treatment.

Types of fertilizers

They are simple, mixed, concentrated, and combined. Primes contain one element; the mixed two or more; complex ones are chemically joined by 2 nutritional elements. Concentrated ones have two or more times the active substance. And according to their origin, they are divided into mineral, organic, organometal, and bacterial.

  •   Organic Organic: contain few nutrients and must be fed in large quantities. On the other hand, we prefer them because they enrich the soil, improve microbial activity, and enrich soil structure and aeration. In addition, they are more economical and environmentally friendly.
  • Wood ash - contains 2-3% potassium and 0.5% phosphorus. It is very rich in potassium and also contains calcium. It can be used for fertilizer without looking for another source of this element. The ash obtained from broad-leaved trees is richer than that from conifers, and that from young trees is richer than from old and thick trees. It can be used in the pre-planting preparation of the plants and in their planting. In young fruiting plantations, ash can be used at any time. Water very quickly washes the potassium oxides from the ash, so it should be kept in a dry place.
  • Composting plant waste - this is rotted organic matter from plant waste. They are slow-release nitrogen fertilizers. They are all placed in a pile. They are watered several times in the summer. They usually sit for a year before being used. Compost that has not yet germinated weed seeds and has not fully decomposed is not recommended.

The benefits of this type are that the physical properties of the soil and its airiness are improved. This is a fertilization method that is not new but has gained particular popularity in recent years. If nutrients are properly managed using this method, soil pollution is reduced and crop fertility is increased. Compost can be applied to agricultural fields as fertilizer, added as a soil structure improver mixed with peat in horticulture, or used as a microbial additive to increase enzyme activity. This directly affects the physiological development of plants.

  • Manure - the content of nutrients is different, depending on the type of the given animal, the forage it is fed with and the bedding it uses. Sheep manure is the richest, followed by bird, horse, and beef manure. It is recommended to use it after it has "burned out" (decomposed). It is best if it has been aged for 5 years before being used. According to the analyses, manure, depending on its origin, can contain from 10 to 30 grams of boron in one ton of dry mass.
Nutrients in different types of fertilizer
A type of manure Water % An Organic Substance %  Nitrogen  % Phosphorus % Potassium % Magnesium %
Horse  70-71 24-25,5  0,56-0,58  0,28-0,29  0,60-0,64 0,10-0,14
Beef 76-77 20-20,5  0,4-0,45  0,20-0,23  0,45-0,50  0,30-0,40


64-65  30-31,6 0,75-0,83 0,21-0,24 0,65-0,67 0,31-0,32
Pork 70-72  23-25  0,44-0,45 0,17-0,19  0,58-0,60 0,14-0,17
Birds 55-57 40-43  1,60-1,65  1,5-1,55 0,83-0,86 2,30-2,45
Mixed 73-75 20-21  0,45-0,50  0,20-0,25  0,55-0,60 0,12-0,15

Good results are achieved when applying the manure concentrated in the soil depth. It has good water-holding properties: 1 kg of fertilizer can hold about 2 liters of water in the area of the root system of plants.

  • Biochar - A new modern technology for soil enrichment is the use of biochar. It processes excess solids and waste products from plant and animal husbandry. It is a complex thermochemical process by which thermal biomass and organic matter are decomposed at a temperature of 500-700 °C in an oxygen-free environment. The finished end product is a mixture of solid (pyrolysis coal), liquid (bio oil) and gaseous (methane, hydrogen, carbon monoxide and carbon dioxide) elements. Their ratio depends largely on the pyrolysis method used, the characteristics of the biomass and the reaction parameters. Pyrolysis charcoal, or biochar, can help reduce carbon emissions that are generally released from the burning and decomposition of woody biomass and agricultural waste. It improves soil characteristics such as structure, acidity and content of organic matter, as well as water availability. It is an organic material that decomposes in the soil over a very long period of time (hundreds of years). This is because it contains many pores and cavities within it and is resistant to microbial decay. Biochar helps to improve the condition of the soil, which affects the proper development of cultural plants. It can be seen not as competitive with composting, but as a complementary technology. Adding it in the early stages of composting can reduce processing times and increase heating temperatures, which kills more pathogens or weed seeds. It helps retain more nutrients and increases long-term carbon content.
  • Green Manuring - Cultivating the inter-row spaces around saplings with different crops brings a number of benefits. It improves nutrient and moisture status, slows down the erosion process (if any), improves soil structure and suppresses weed growth. Green (cover) crops provide many benefits, but they must be chosen correctly. Sowing such crops enriches the soil with nitrogen in a natural way. A large part of it is contained in plant residues and self-sowing plants. Once in the soil, they can be digested for up to three months. A basic principle when using green crops is to look for and cover all periods during which the soil remains without vegetation cover and is exposed to natural forces. We recommend that after harvest, plant residues are not burned, but plowed instead. Thus, the soil will be supplied with more nutrients. Some bacterial fertilizers fix atmospheric nitrogen, which is almost completely absorbed by plants. This influence of microorganisms has long been known in agriculture - legumes increase soil fertility by absorbing atmospheric nitrogen.
  • Biohumus is one of the most basic ways to preserve and enrich soil fertility. It is only necessary to maintain the population of garden worms. They live for about 16 years and feed on various types of manure and other organic waste. Through their processing, soils become more nutritious for plants and improve the water-air composition of soils. As a result of their movement, small channels are formed through which the necessary water is filtered, so that the roots do not rot.
  • Microbial fertilization is the introduction of beneficial bacteria into the soil. Through them, the soil becomes more saturated with oxygen and organic substances, the time for decomposition of plant residues is reduced and the unavailable nutrients are converted intothe soil in accessible forms. These are spore-form organisms that can capture ammonium film from the atmosphere. They build a connection between the plant and the environment by attracting beneficial microorganisms to the root zone, which support nutrition and protect the plant from diseases and harmful microorganisms. In this way, the need to spray pesticides is reduced or completely eliminated. This type of fertilization requires deep knowledge and a detailed analysis of the soil and the environment in order to achieve the desired effect of their application.


Where to do the fertilizing?

The most feeding roots are below the periphery of the crown and beyond. The thick roots are located around the trunk, along which there are almost no such nutrients and they cannot absorb the substances from there. Fertilizers should be distributed under the entire crown and about 0.5 m beyond it, where they will be best absorbed. When the soil is cultivated at a depth of 10 cm, more than 37% of the surface roots of the walnut are damaged, and when cultivated up to 20 cm, 65% of them are damaged. (p. 49 Dragan Brezovski) Other options for fertilization have been developed without requiring mechanical treatment of the land. In addition to mechanical fertilization, nutrients can be supplied to the soil by other modern methods.

Fertigatsi – this is a system for micro-irrigation and the introduction of concentrated fertilizers through the irrigation water. This happens through pipes that are buried under the soil. The solution is injected into a system. In order to avoid clogging, it is necessary to have the absolute aqueous dissolution of the substances. Excellent and fast results are achieved when calculations are made for the size of the space to be improved. Nutrients are easily absorbed by plants without much loss. It is advantageous because it allows it to be entered at small intervals. It is usually fertilized every one, two weeks or continuously. Through it, the necessary nutrients needed during the entire vegetation can be maintained. In this way, the need for pre-planting and periodic fertilization is eliminated. When drippers or micro-jets are used to wet only the border of the trees, the tree roots are concentrated right there and the absorption of the fertilizer by the tree is efficient and fast. When feeding plants, the irrigation cycle should be shorter than usual and the fertilizer should be applied in the last 30 to 60 minutes of watering. It is best if this happens a day or two after rain or irrigation so that the fertilizer is applied while the soil is still moist. A fertilizer's ability to dissolve in water is not always a good indicator of nutrient uptake. It is desirable to determine the fertilization rates and their composition on the basis of soil and leaf analysis.

Foliar application of nutrients - There is a faster effect of feeding when it is carried out by spraying substances on the leaves of the tree. It is necessary to spray from both the upper and lower sides. Thus, nutrient deficiency is quickly corrected. They are suitable when there are disturbances in small areas of an orchard or in random trees. If we compare fertigation and foliar spraying, we will find that the latter can be more expensive in terms of products and machinery needed for the application. In addition, increased attention to atmospheric conditions is necessary. Very hot days should be avoided when the strong sun can cause the leaves to burn. In very hot weather, the solution evaporates before the plant can absorb it. This method should also be avoided when there is rainfall that can wash the substances off the leaves.

PH analysis - The most important analysis to start with is related to soil Ph testing. If the value is not within the moderate limits, then it will be difficult for the plant to absorb the necessary elements and have a good development. The walnut tolerates a wide range of ph - from 5 to 8, but it develops best when the value is 6.5. There are different methods of fixing this value. A good supply of nutrients depends on the composition of the soil. If the ph value is above 5, nitrogen becomes available to plants, if it is above 6 and 7, then phosphorus becomes more available. When lime is added to the soil, the acidity is reduced, hence the possibility of absorption of phosphorus by the plant. Crops such as alfalfa and soybeans contain bacteria around their roots that make the availability of nitrogen in the soil higher. On the other hand, in very acidic soils, plants can hardly absorb nitrogen, phosphorus, and potassium. Acidic soil does not need nitrates. Slightly acidic soil reacts favorably to ammonium-nitrate fertilizers. Alkaline soil must be enriched with compounds to balance its composition. Otherwise, the plants develop poorly and their leaves turn yellow because they cannot absorb the required amount of iron. We recommend in this case sprinkling pine needles in the soil (they can be pine, fir, or spruce). When they decompose, the acidity of the soil increases. When the ph value is low, lime is added to raise it. This happens naturally in areas where the water is more calcareous. There are various and affordable ways to analyze the ph composition of the soil. We strongly recommend that at least one of these be carried out in order to be able to timely and quickly track the need of the walnut tree.

What impact does the individual element have?

Nitrogen - participates in building proteins. It accumulates as a reserve in the roots, stem, and skeletal branches. It mainly affects the increase in growth and fruiting. It determines the size and color of the leaves and the setting of the fruit buds. During the first three years, trees need about 100 grams of N per tree. The rate of fertilization is best determined after a soil analysis. After the trees reach 4 years and start production, the amount of N should be higher. In young plants, an abundant supply of nitrogen continues growth until late autumn, which is not good for the hardening of plants, they become especially sensitive during the winter season. The best time for fertilizing is March-April, before the start of vegetation. It is not advisable to fertilize in autumn, except when there are green crops planted around the walnuts. In the first year of the plant's life, do not fertilize. Its deficiency is recognized as the lightening and thinning of the leaves. Shoots have poor growth. In autumn, the leaves turn yellow and fall prematurely. It is recommended not to fertilize with nitrogen in the first year, and from the 2nd to the 5th year to use 160-200 g/tree nitrogen (N), 6-7-year-old tree - 200-300 g/tree nitrogen ( N) and for 8-10-year-old trees 300 g/tree of nitrogen (N).

Phosphorus also participates in the construction of proteins, helps the accumulation of sugars, and is absorbed by the plant when it is applied to a depth of 40 cm. It is best when watering is carried out immediately afterward, so through the water, it will go down into the soil layer. It is used in autumn and is associated with deep processing. In order not to damage the structure of the roots, they can be imported every 2-3 years. We recommend that it be applied 20 cm from the soil layer and then sprinkled with water so that it can reach the desired depth where it will be absorbed by the roots. It is good to use it before planting the tree in the planting pit, covering it with 5 cm of soil to avoid burning the roots of the plant, as a quantity of 0.5-1 kg can be used. In case of deficiency, the growth weakens, the yield decreases, and the shoots remain thin.

Potassium It has an electrochemical catalytic function, regulates respiration, and photosynthesis supports the root extraction and the setting of fruit buds. It affects the cold resistance and quality of the fruits. It also helps resistance to fungal diseases. The balance between potassium and nitrogen is very important for the good yield and quality of the nut. When applied superficially, it is retained up to a depth of 10 cm. In case of deficiency, the growth weakens, the yield decreases, and the shoots remain thin. The leaves in summer become small, turn white, and later curl up and turn gray at the bottom. In autumn, leaf shedding proceeds from the tip to the base. Corrective fertilization is carried out in holes with a depth of 10-15 cm or on the soil surface. Potassium is not washed outthe soil. The recommended annual rate of potassium is 7-20 kg/ha of potassium (K2O). A suitable period for fertilizing is early June.

Calcium - deficiency is rare, but can be corrected by applying CACO3 at 500 to 1000kg./ha. The low content in the soil solution can also be stimulated by adding magnesium. When the calcium level is normal, the presence of magnesium can slow its absorption.

Magnesium - in case of identified deficiencies of this element, 100 to 200 kg/ha are added. Depending on whether it is low or medium stocked. In magnesium-poor soils, it is good to plow before planting.

Boron – it is presentedin the soil solution as neutral boric acid. It participates in the construction of cell walls, flowers, and fruits. It also stimulates plant growth. In case of deficiency, weak growth is noticed, the shoots have short internodes, and the trees themselves look like bushes. When there is a serious shortage of pine, long shoots without leaves are noticed, mainly on the top of the tree. These shoots die the following winter. With a moderate deficiency of pine, a drop in fruit yield from apparently healthy trees is noticed. A suitable period of fertilization is 14 days before flowering (April, May) or after harvesting, but the effect is significantly less (with a norm of 55-85kg/ha). It lasts from 3 to 5 years and stops when the symptoms disappear.

Zinc - Walnuts are very sensitive to zinc deficiency. A characteristic deficiency is observed in soils treated with manure. Excess phosphorus interferes with the absorption of zinc. Zinc is needed for the opening of the buds and for the elongation of the walnut shoots. Facilitates overcoming extreme heat and dealing with diseases and drought. It has a very significant role in the regulation of nucleic acid functions (heredity, genes) and protein synthesis. Zinc is a co-factor in over 300 enzymes. In the walnut, zinc plays an important role in pollen formation, color, pollination, and yield. When there is a deficiency of zinc the leaves and fruits are small. The edges of the leaves curl upwards. Foliar fertilization is recommended in April-May or immediately after harvesting before leaf fall, but the effect is less. Walnuts have the highest zinc needs in the spring during spring growth. The recommended rate per tree is 10 kg of zinc and 5 kg of sulfur. Dissolved sulfur from the irrigation water keeps the zinc in a soluble form. It is introduced into the soil by deep plowing.

Iron and manganese - their availability depends on the solubility of their oxides. Fertilization with iron and manganese is carried out after soil amendments with sulfur, nitrogen fertilizers or ammonium sulfate have been made. Insufficient oxygen can result in an increased content of iron and manganese ions, which is toxic to root development.

Analysis methods

Nutrient uptake levels can also be determined by leaf analysis. It is done by randomly sampling trees in each block. Samples should consist of 50-100 leaves, including petioles. The collection of walnut leaves for sampling should be from shoots of medium vigor from trees of the same variety selected at random. Samples of damaged or old leaves from the middle of the tree are avoided. The most suitable time for analysis is the month of July when there is the least change in concentrations. Three levels of nutrient concentration are distinguished:minimum, optimum and excess. This analysis is more accurate than the soil analysis, but also more expensive. It would be best if both are combined to achieve optimal results.

Chemical analysis of the soil

Soil analysis is important to determine the soil reaction in order to develop the walnut plantation properly. There is more than one method by which to clarify the composition of the soil. Changing conditions and increased consumption leads to the development of the technical means used. Tillage improves physical, water, and air properties. It is important for obtaining a larger quantity of the grown produce. Various techniques are used to preserve the properties of soils. Applying minimal tillage to the soil is important to preserve its characteristics. Frequent processing causes compaction and dusting, and hence water and wind erosion. Minimal cultivations allow several activities to be carried out (sowing with seed drills equipped with bodies for applying fertilizers and herbicides and harvesting and watering).


There is a law that specifies values for optimal fertilization and optimal nutrient yields for types of plantations. It was created to clarify known application limits of mineral fertilizers. When applying amounts above the given levels, there are no proven improvements in production yields, but excess nutrients are considered toxic. This can lead to contamination. Fertilization can also be effective with available natural resources. When solid waste is converted into compost rich in organic compounds and no toxic, highly persistent biochemicals are used, a large amount of arable land can be preserved. Modern nature-ethical methods are needed to influence the wealth, fertility, and ecology of the soil in order to preserve its diversity but in a way that is protected and suitable for it.

 In conclusion, it should be emphasized that the introduction of fertilizers into the soil, both natural and artificial, must be done in accordance with generally accepted norms, rules, and technologies. Disruption of fertilization systems can lead to undesirable ecological and social consequences, expressed in the destruction of the environment, and the soil structure, the deterioration of the quality of agricultural production, and the deterioration of the health status of the population. In the past, when there were no mineral fertilizers, people used composted plant and organic residues. Yields were low with high nutritional qualities. Later, science discovered which mineral substances plants needed to maintain their productive potential, and thus soil fertility increased significantly. With chemical fertilization, the yields are undoubtedly increased, but when high doses are used, the soil is polluted. This also happens with inert impurities that are included in the composition of fertilizers. Introduced in larger quantities, they are carried from the surface waters into the underground and permanently pollute them. The use of pesticides for plant protection pollutes the soil. Very careful and timely handling is needed to reduce the quantities and their risk of them. Soil is a living system that provides life on earth. By implementing our actions, we have a responsibility to her and to the future generation. There are ways to get what we need without conflicting with nature.