Proper nutrition of the plant is one of the fundamental factors for good growth, profitable production, and standard quality of raspberry and blackberry fruits. The fertilization of these crops depends on: soil texture, soil pH reaction, and the presence of organic matter in orchards. Before planting, soil analysis must be performed to determine the presence of each macro and microelement in the soil, as well as the soil pH reaction. Also, during the growing season, leaf analysis should be performed to determine nutrients in the plant and to determine the state of nitrogen and potassium leaching in the soil. In this way, the necessary amount of nutrients to be used for raspberries and blackberries is determined. The growth vigor and habitus of the plant, the thickening of the shoots, the size and color of the leaf, are indicators of the plant's health status, as well as the need for fertilization. Raspberries and blackberries are usually fertilized with fertilizers in a combination of four methods: the use of manure manure, the distribution of mineral fertilizers in grain form, water-soluble fertilizers, crystalline fertilizers in the irrigation system, and the use of microelements through foliar treatment. Most fertilization from all methods depends on the nutrient content in the soil, the natural fertility of the soil, and the existing potential of the irrigation system. If there is no irrigation system, fertilization can be done by spreading manure from the manure and artificial fertilizer grains.
Fertilization with barn manure
Since stable manure is more valuable and easy to find, but with low nutrient content, it is recommended to use one ton per 0.10 ha and represents a very important fertilization program. The nutrient content in manure in manure has an irregular ratio between nitrogen, phosphorus, and potassium (N-P-K). Moreover, manure acts slowly. According to research, such manure acts for a period of up to three years. In the first year, 50% is used, in the second year 30%, and in the third year 20%. Therefore, following the usual practice in raspberry and blackberry orchards, burnt cattle manure should be used every third year in amounts of 1–2 tons per 10 ares, depending on the fertility of the soil.
Poultry manure with a high nitrogen content is recommended to be used in amounts of 0.5 – 1.0 tons per 10 ares. If the stable manure is prepared according to all criteria, its use can be done at any time during the season. Only the use of well-burned barnyard manure is recommended. When using organic fertilizers, especially unburned barn manure that is not inactivated and contains non-structural materials, it is difficult to spread in the gutters. In addition, unburned manure contains seeds of various weeds as well as many pests and pathogens that cause diseases. Burnt barn manure, with organic matter broken down at the appropriate scale, can be easily spread with a shovel or pitchfork and has multiple effects: it improves and preserves soil structure, increases soil fertility, stimulates the development of beneficial microorganisms, etc.
Research has shown that one ton of burnt manure used in raspberry and blackberry orchards contains 2 kg of effective nitrogen. Compost and straw mixed with manure represent a valuable supplement to organic matter in the soil but have less nutritional value compared to pure manure.
In raspberry and blackberry orchards, the organic matter in the form of barn manure is applied in autumn, after removing the shoots that have borne fruit. Such fertilizer affects the increase of nutrients in the soil and warms the plants during the winter period. Organic manure can be used in such a way that on both sides of the row shallow furrows are dug, at a distance of 45 cm from the shoots, these are filled with manure, and finally covered with soil. During soil preparation for raising raspberry and blackberry orchards, compost or manure should be spread into the grater or raised beds before planting, at a depth of 10 cm. Stable manure can also be used after planting, at the time when the plants reach a height of 8 cm. Fertilization with barn manure should be used once a year in raspberry and blackberry orchards, but it should not be the sole source of nutrients. In addition to manure, the use of mineral and water-soluble fertilizers is also recommended.
Fertilization with mineral fertilizers in the form of grains
The three most important elements for raspberries and blackberries are: nitrogen (N), potassium (K), and phosphorus (P). For the growth of these crops, regardless of the type of growth, approximately 3.5 kg of nitrogen per 0.10 ha should be used in the first year. However, the use of mineral fertilizers in the first year should be avoided until the shoots appear. Because young raspberry and blackberry plants are very sensitive and can be damaged by the increased concentration of salts in the soil. In the following years, for biennial raspberry and blackberry varieties, nitrogen (N) should be used at 7.5 kg/0.10 ha, while for one-year-old varieties of these crops, nitrogen at 11 kg/0.10 ha should be used. Phosphorus should be applied annually in amounts of 2.5–3 kg/0.10 ha. Potassium should also be applied every year, but in amounts of 5–6 kg/0.10 ha. Fertilization of biennial raspberry species should be done two or three times a year. It is better to fertilize in spring, when new growth begins, the second after May or early June, and the third in mid-July. In this case, the use of manure from the stable should also be considered to reduce the amount of mineral fertilizer.
If burnt barn manure is used, in this case the appropriate amount of nitrogen is 50%, but if fresh stable manure is used, the appropriate nitrogen amount can be 90%. When using mineral fertilizers, this moment should be taken into consideration. Mineral fertilization is done in rows 25 - 30 cm away from plants and inserted into the soil at a depth of 5 - 10 cm. Fertilization of raspberries and blackberries is done in combination: NPK 10:20:30, 10:12:26; CAN and UREA. Each year, stable manure is used at 400-600 kg/ha NPK, and in years when organic fertilizers are not used, the amount of mineral fertilizers is increased to 600-700 kg/ha. Spring fertilization represents supplementary fertilization and is done with nitrogenous mineral fertilizers, CAN or URE, in amounts of 200–300 kg/ha. If necessary, a second supplementary fertilization can be done to eliminate the appearance of nitrogen deficiency symptoms, with CAN or UREA, in amounts of 150–200 kg/ha.
Fertirigation – fertilization through irrigation
Before planting raspberries and blackberries, about 25% of the total amount of nitrogen, phosphorus, potassium, and micronutrient fertilizers can be used for fertilization. The remaining amounts of fertilizers with N, P, K can be used during the growing season through the irrigation system. Through this system, adjustments can be made as well as the use of the remaining amount of N, P, K if these have not been used in granule form or mixed with stable manure. On larger plots, pure nitrogen can be used in amounts of 3-5 kg/0.10 ha, pure phosphorus 1.5–2.0 kg/0.10 ha, and pure potassium in amounts of 3–4 kg/0.10 ha. These fertilizers should be applied in the middle of the shoot growth phase in spring and during the harvest phase. Nitrogen should not be used after mid-August. In soils rich in organic matter, the entire amount of N, P, and K can be utilized through the irrigation system, which ensures successful growth and good production. At least 50% of the nitrogen should be in nitrate form. Better results in the quantity and quality of raspberry fruits are achieved if N and K are used through the irrigation system or in the form of seeds. When mineral fertilizers are used in this way, the frequency of their use matters little compared to the amount of fertilizer used. Using a smaller amount of fertilizer several times through the irrigation system can, in most cases, help reduce leaf burns caused by the high concentration of salts in the soil. Water-soluble fertilizers are applied for a duration of 1-2 hours a day or every other day during the flowering and fruit formation phases. Commercial water-soluble fertilizers most often consist of nitrogen (N) and potassium (K). Concentrated fertilizers are easier to concentrate, are used in a very short time, and the amounts of nutrients are added to the soil. When using mineral fertilizers with irrigation, cases of system closure should be avoided, while fertilizers used in this way should be water-soluble. If several materials are used during irrigation, the mineral fertilizers in combination should not react with each other. Other chemical compounds used in this way must be compatible with the other elements used through the irrigation system. Such fertilizers with high or low pH are corrosive to copper, zinc, bronze alloys, and other metal parts of the irrigation system. For this reason, irrigation system components that come into contact with corrosive fertilizer mixtures must be made from corrosion-resistant steel, plastic, or other materials.
The fertilizers used through the irrigation system are: urea, potassium nitrate, ammonium phosphate. Phosphorus in the soil moves significantly if used through the irrigation system in smaller amounts. Raspberries and blackberries mainly need phosphorus early, so it is important that this element is used during planting or immediately after planting. Phosphorus-based fertilizers used through the irrigation system can react with potassium in water and form insoluble forms, which results in the closure of pipe holes. However, if the rules for using such fertilizers are followed through the irrigation system, this problem can be successfully avoided. The solution to this problem can be acidification of phosphoric acid in storage, mixing with sulfuric acid, or injecting sulfuric acid immediately after injecting phosphoric acid. Injecting acidic solutions into the irrigation water prevents phosphorus residue, but without harmful effects on the soil.
The use of micronutrient fertilizers through leaves
The shelf life of foliar fertilizers containing microelements is very limited. For this reason, more damage can be caused to raspberry and blackberry crops if these are used in large quantities. If the analysis confirms the absence of any microelement, the proper use of the specific microelement through foliar treatment may be sufficient to eliminate the detected disorders. Such treatments with microelements can be done every 10 days until the complete elimination of symptoms caused by their deficiency. Fertilizers formulated with microelements are added to the moistening agent if they do not contain such substances. Fertilizers for foliar treatment are not used during the flowering stage of raspberries and blackberries because they may have a phytotoxic effect on the flowers. Micronutrient fertilizers in grain form used for soil treatment do not have as much effect as micronutrient fertilizers used for foliar treatment.
Leaf analysis
For the proper adaptation of the fertilization program, tree growers must check the nutrient content in raspberry and blackberry plants every year. In accordance with the results of tissue analyses, it is necessary to undertake fertilization measures for the crops. To accurately determine these parameters, the leaves of these crops must be analyzed. For this purpose, 5 mature leaves along with the stem are taken from each plant, and in this way, a representative sample for analysis is formed. Undoubtedly, the selected plants from all parts of the orchard must be analyzed to determine that abnormal manifestations are related to nutrients. The optimal quantity, the amount below the optimal, and the maximum are presented in Table 2. A decline in production can occur if the amount of nutrients is below or above the optimal level.
Symptoms of nutrient deficiency
The nutritional status of raspberries and blackberries can mostly be determined by the external appearance of the plant's leaves. Symptoms of insufficient fertility can often be identified by specific signs for certain elements. Each of the macro and microelements shows characteristic symptoms of their deficiency in the plant. Visual diagnosis of the signs of nutrient deficiency in raspberry and blackberry plants is the second way growers can determine the fertilization regime and overcome fabricated problems. However, orchard damage is caused before the appearance of obvious symptoms. If the nutrient deficiency improves earlier, then plants can more easily overcome such a condition. Typical symptoms of nutrient deficiency in raspberry plant leaves are described in the following table and illustrated with photographs
Burns on the leaf edges and the appearance of a chestnut color on raspberry leaves are signs of potassium deficiency. Such leaves curl toward the underside, while the burned parts on the leaf surface appear twisted
Magnesium deficiency appears as yellowing of the old leaves, starting from the edges but spreading to the inner surface of the leaf
Iron deficiency appears with severe yellowing of the leaves and young shoots
