Stone fruits – also known as drupaceae – found the climate suitable for production in the southern and southeastern states of Brazil. In addition, research and genetic improvement have helped select varieties that are most adaptable to regional conditions. According to data from Embrapa, the states in the southern region of Brazil have the best natural conditions for the commercial production of plums and other stone fruits. Rio Grande do Sul is the largest national producer, with an average of 128,568 tons per year, corresponding to 63.8 % of the country's total production. It is followed by São Paulo, with 33,734, Santa Catarina, with 17,790 and Paraná, with 10,641 tons per year. Among the group of stone fruits produced in Brazil, peach production stands out (Prunus persica vulgaris L.), followed by plum (Prunus salicina L.) and nectarine (Prunus persica nucipersica L.), with the area with peach trees representing more than 80 % of the cultivated area (Fachinello et al., 2011). Other stone fruits such as cherries and apricots have insignificant production.
According to Rombolà et al. (2012), the nutritional requirements of drupaceae at full production capacity vary greatly depending on the species and rootstock adopted, increasing significantly according to the production volume. At this stage, nutrient exports are determined by the growth of perennial organs, pruned wood, fallen leaves, and fruits. At this stage, two minerals are essential: nitrogen (N) and potassium (K), which must be used in orchard maintenance fertilization. However, it is important to mention that inadequate fertilization can cause damage to plants, thus leaving them more susceptible to phytopathogens. In general, excess nitrogen and lack of potassium in plants increase the intensity of occurrence of diseases, such as brown rot, bacterial blight, branch blight, among others, as cited by Mayer et al. (2019).
How does potassium act on plants?
Potassium is an essential macronutrient for plant growth and development that affects several fundamental physiological processes (Clarkson and Hanson, 1980). It is the most abundant cation in plant cells and can be stored in the cytoplasm and/or vacuole, while the distribution of K concentrations between these compartments determines its function in the plant (Marschner, 1995). Furthermore, K is characterized by high mobility, not only in short-distance transport, such as between individual cells and neighboring tissues, but also in long-distance transport – through the xylem and phloem. These characteristics make K the main nutrient responsible for controlling several physiological and biochemical processes in plants, such as: enzyme activation, regulation of cellular osmotic potential, neutralization of soluble and insoluble molecular anions, and stabilization of cellular pH (Marschner, 1995).
Potassium plays an integral role in plant-water relationships and is related to numerous physiological functions where water is involved, including transpiration, maintenance of cell turgor, stomatal opening and closing, and enzyme activation. In addition, it acts in photosynthesis and translocation of photosynthesized organisms, as it is indirectly related to the synthesis of the enzyme RuBisCO – responsible for catalyzing the reactions necessary for the assimilation of CO2 and subsequent conversion into glucose. As already mentioned, due to the fact that K is related to enzymatic activations, it is also capable of promoting plant resistance to biotic and abiotic stresses.
For stone fruit trees, as already mentioned, the main mineral elements that plants need are nitrogen and potassium. K participates directly or indirectly in numerous biochemical processes of plants and is involved in carbohydrate metabolism, photosynthesis and respiration (Song et al., 2015). In orchards, potassium fertilization is related to fruit quality (Nava et al., 2008; Lester et al., 2010). K is an extremely important nutrient for fruit quality, promoting more intense color and improving flavor. Because it is related to aspects such as carbohydrate transport through the plant, adequate K nutrition promotes the development of larger and sweeter fruits and, therefore, with high commercial quality, since it maintains the balance between sugar and acid levels and improves storage potential. However, excess of this nutrient can reduce the storage potential of fruits after harvest and inhibit magnesium absorption, accentuating imbalances and reducing post-harvest durability (Cuquel et al., 2004).
Symptoms of Potassium Deficiency in Stone Fruits
K deficiencies result in alterations in numerous physiological functions, including water relations, enzyme activation, ion charge balance, poor growth, reduced yield and reduced resistance to stress (Oosterhuis et al., 2014). Initially, necrotic spots appear on the leaves along almost the entire edge of the blade, progressing towards the central vein, but without, however, reaching the entire leaf. The edges of the leaves curl upwards until they touch, forming a characteristic cartridge. Because K is a highly mobile element in the plant, symptoms are first observed in older leaves. Then, under deficiency, K moves easily to the leaves that are growing and, therefore, require a greater demand (Fernandes et al., 2006; Yost et al., 2011).
Potassium is associated with the lignification process of sclerenchyma cells, giving plants increased leaf and fruit skin thickness, promoting resistance to pests and diseases. When potassium is deficient, plants become susceptible to diseases, reducing fruit production and quality (Serrat et al., 2004), and stone fruits are very vulnerable to deficiency of this element (Malavolta et al., 1997). Especially in peach crops, K deficiency is associated, in many studies, with brown rot infection (Monilinia fructicola Winter) – the main disease of stone fruit trees, especially during the flowering and final stages of fruiting. The coincidence of environmental conditions favorable to the disease with the fruiting period favors the rotting of fruits still on the plant, causing mummified fruits that can serve as a source of secondary inoculum (Hong et al., 1997).
ETIXAMIN KALLY® – Exclusive ILSA Brasil technology
Due to the importance of potassium for stone fruit trees, an adequate supply of this nutrient can be a determining factor for good production. ILSA Brasil recommends the use of the organomineral fertilizer ETIXAMIN KALLY®, formulated in soluble powder for application via foliar application or fertigation. This fertilizer is produced from GELAMIN®, an organic matrix manufactured from collagen and, therefore, characterized by a high concentration of nitrogen, amino acids and organic carbon, obtained through an innovative and sustainable industrial process called Fully Controlled Enzymatic Hydrolysis (FCHE®).
In addition to K and N, ETIXAMIN KALLY® simultaneously provides amino acids and sulfur, which sets it apart from similar fertilizers. OK, as already mentioned, is essential for fruit quality, as it is associated with the translocation process of sugars and organic acids, contributing to the ideal balance between acidity and soluble solids content. Amino acids, in turn, are activators of enzymes and phytohormones, which act directly and indirectly in the photosynthetic process and, consequently, in the transport of sugars in the plant.
Fertilization with ETIXAMIN KALLY® increases fruit quality and also favors resistance against biotic and abiotic stresses, since potassium, as already mentioned, is directly related to enzyme activation, promoting crop protection, in addition to increasing the lignification process of the leaf cuticle and cell wall, which prevents the entry of phytopathogens and the progress of infections.
In addition, this fertilizer stimulates photosynthesis and many other metabolic processes, promoting balanced plant growth and increasing productivity. Furthermore, as it is a sustainable technology in all its production processes, ETIXAMIN KALLY®, like all ILSA Brasil fertilizers, has a low environmental impact.
ILSA Brazil Fertilization Plan for Stone Fruit Trees
Figure 1. Peach tree phenological phases and ILSA fertilization plan.
In addition to ETIXAMIN Kally®, ILSA Brasil also offers other organomineral fertilizers manufactured from the matrices GELAMIN® (base for foliar application and fertigation) and AZOGEL® (base for solids applied via soil), which can be applied throughout the entire production cycle of drupaceae, improving the quality of the plant stand. For foliar application, ILSA Brasil also recommends the fertilizer ILSAMIN Boro®, indicated for the entire flowering period, as it stimulates the process of pollen tube development and flower opening, preventing floral abortions and also promoting resistance to abiotic stresses. For drupaceae under fertigation systems, ILSADRIP Forte®, which can also be applied via foliar application, is recommended for the supply of amino acids in all stages of plant development – vegetative and reproductive, especially during periods of abiotic stress, as it enhances the plant's metabolic processes and increases productivity.
The AZOGEL® matrix is used to obtain the AZOSLOW® and N-TIME+® fertilizers, which can be applied in the early stages of development, gradually providing organic nitrogen (N) and carbon (C) in addition to amino acids, ensuring high absorption efficiency and, therefore, avoiding losses due to volatilization. Gradual MIX® is also recommended for all vegetative and reproductive stages of the plant, in addition to the post-harvest period, as it is a soil fertilizer with NPK and rich in amino acids, which have formulations for both budding (GM 10 18 07) and coverage (GM 08 00 28).
It is important to mention that fertilization in orchards must be rational, which presupposes the appropriate use of fertilizers, avoiding insufficient or excessive applications, in order to provide the orchard with the nutrients that are actually needed, in the appropriate quantities and at the appropriate times, while simultaneously preserving the environment. To this end, it is necessary not only to know the state of soil fertility, but also to know whether the nutrients present there are being effectively used by the crop. Therefore, the doses to be used are not described in the text, as they should be based on soil analysis and on the recommendation of an agricultural engineer.
Bibliographic references
CLARKSON, DT, AND JB HANSON. The Mineral Nutrition of Higher Plants. Annu. Rev. Plant Physiology, vol. 31, p. 239-298, 1980.
CUQUEL, FL; HADLICH, E.; CALEGARIO, FF Postharvest in stone fruit trees. STONE FRUIT TREES: An ecological view. 2004. p. 317 – 331.
EMBRAPA – Brazilian Agricultural Research Corporation. Available at: https://www.embrapa.br/agencia-de-informacao-tecnologica/
FERNANDES, MS Mineral Nutrition of Plants. 1st ed. Viçosa: UFV, 2006. 432 p.
HONG, C.; HOLTZ, BA; MORGAN, DP; MICHAILIDES, TJ Significance of thinned fruit as a source of the secondary inoculum of Monilinia fructicola in California nectarine orchards. Plant Disease, v.81, p.519-524, 1997.
LESTER, GE; JIFON, JL & MAKUS, DJ Impact of potassium nutrition on postharvest fruit quality: Melon (Cucumis melo L) case study. Plant and Soil, vol. 335, n. 1-2, p. 117–131, 2010.
MALAVOLTA, E.; VITTI, GC; OLIVEIRA, SA Assessment of the nutritional status of plants: principles and applications. Piracicaba, Potafós, 2 ed., 1997. 319 p.
MARSCHNER, H. Mineral Nutrition of Higher Plants. 2. ed., San Diego: Academic Press, 1995. 889 p.
MAYER, NA; FRANZON, RC; RASEIRA, MCB Peach, nectarine and plum: the producer asks, Embrapa answers. Embrapa, Brasília, 2019. 296 p.
NAVA, G.; ROQUE-DECHEN, A. & RIBEIRO-NACHTIGAL, G. Nitrogen and potassium fertilization affect apple fruit quality in southern Brazil. Communications in Soil Science and Plant Analysis, vol. 39, no. 1-2, p. 96-107, 2008.
OOSTERHUIS, DM; LOKA, DA; RAPER, TB Potassium and Stress Alleviation: Physiological Functions and Management in Cotton. International Potash Institute, vol. 38, p. 19-40, 2014.
ROMBOLÀ, AD; SORRENTI, G.; MARODIN, GAB; DE PIERI, AZ; BARCA, E. Nutrition and soil management of stone fruit trees in temperate climate regions. Semina: Agricultural Sciences, Londrina, v. 33, n. 2, p. 639-654, 2012.
SERRAT, BM; REISSMANN, CB; MOTTA, ACV; MARQUES, R. Mineral Nutrition of Stone Fruit Trees. Stone Fruit Trees: An Ecological View, p. 71 – 96, 2004.
SONG, Z.; GUO, S.; ZHANG, C.; ZHANG, B.; MA, R.; KORIR, NK & YU, M. KT/HAK/KUP potassium transporter genes differentially expressed during fruit development, ripening, and postharvest shelf-life of 'Xiahui6' peaches. Acta Physiologiae Plantarum, vol. 37, no. 7, p. 131, 2015.
YOST, MA et al. Potassium management during the rotation from alfalfa to corn. Agronomy Journal, vol. 103, no. 6, p. 1785- 1793, 2011.
Authors
- Agricultural Eng. Msc. Aline Tramontini dos Santos
- Agricultural Eng. Msc. Carolina Custodio Pinto
- Agricultural Eng. Msc. Thiago Stella de Freitas
