Fertilization management of geranium

Geranium belongs to the genus Pelargonium. There are more than 250 species of geranium and a variety of hybrids. The main species are horseshoe leaf geranium (ZonalPelargoniums, Latin name Pelargoniumxhortorum), ivy leaf geranium (P.peltatum, English Ivy-LeavedPelargoniums), and imperial geranium (English name RegalPelargoniums, Latin name Pelargoniumxdomesticum) and so on.

The production of geranium requires an adequate supply of nutrients and a slightly sour pH value. This paper mainly summarizes the nutrition problems in the production of geranium, including horseshoe leaf type geranium, ivy leaf type geranium and imperial geranium.

The pH value, EC value and nutrition level suitable for the growth of geranium are shown in Table 1. The determination methods in this paper are all the values of saturated leaching solution. The index parameters required by different kinds of geraniums are also different, and the function, deficiency symptoms, poisoning symptoms and fertilization methods of each nutrient element will be described in detail below. For example, if the geranium is fertilized and then watered, 20% of the nutrients will be leached, and the EC value will be reduced. If you use underground irrigation or reduce the number of watering, the amount of nutrients can be reduced by 25% to 50% to achieve a similar effect as the former. The deficiency symptoms and poisoning symptoms of the horseshoe leaf type geranium are shown in Table 2.

PH value: the appropriate pH value varies with the type of geranium and the culture medium used. For the horseshoe leaf type geranium, the pH value of the substrate should be between 5.8and 6.2.If the geranium is cultivated in soil, the pH value of the substrate should be between 6.0and 6.5.If the geranium is cultivated in soil, it is suitable for the geranium with horseshoe leaf to be cultivated in soilless culture. For ivy leaf type geranium and emperor geranium, the suitable pH range is 0.3 units lower than that of horseshoe leaf type geranium. If the pH value of the soil needs to be adjusted, acid fertilizer or acid injection can be applied to reduce the pH value, and lime or hydrated lime containing dolomite can be used to increase the pH value.

Electrical conductivity (EC) value: for horseshoe leaf type geranium and emperor geranium, the suitable EC value is 1.5 to 2.5mS/cm, while that of ivy leaf type geranium is slightly lower than this value. Producers can use water leaching to reduce the EC value of the matrix, or they can use the method of reducing the amount of fertilizer application. If the EC value is low, it is necessary to increase the amount of fertilizer application, especially the EC value of the matrix around the root.

Nitrogen element (N): the function of nitrogen element is to synthesize amino acids, proteins, enzymes and nucleic acids. When nitrogen is deficient, the plant will grow slowly, ossify, aging ahead of time, the lower leaves lack green and yellowing, and the leaves fall off ahead of time. When nitrogen deficiency is serious, plant development slows down and flowering is delayed. Geranium is sensitive to ammonia nitrogen (NH4+) poisoning, characterized by old leaf curl, leaf discoloration or necrosis. When fertilizing, the amount of nitrate nitrogen (NO3-) accounts for more than 75% of the total nitrogen, which will avoid the symptoms of ammonia nitrogen poisoning. For geraniums with horseshoe and ivy leaves, the concentration of nitrogen can be between 200ppm and 250ppm. The emperor geranium needs less nitrogen, and the nitrogen sources in the fertilizers of calcium nitrate, potassium nitrate, ammonia nitrate, 20Mel 10Mel 20 or 15Mel 5Mel 25 are more beneficial to the plant.

Phosphorus element (P): the role of phosphorus element in plants is to provide energy transformation (ADP), nucleic acid, enzyme, cell membrane composition and so on. It not only plays an important role in the development of roots and flowers, but also stimulates the rapid growth of plants. The first symptom of phosphorus deficiency is that the plant is ossified and the leaves turn dark green. When the deficiency of phosphorus is more serious, the lower leaves of the plant will turn purplish red, then wilt and turn yellow, or even completely necrotic.

Too much phosphorus can also slow plant growth and lead to the lack of many elements, such as iron, zinc, copper and manganese. The fertilization concentration of phosphorus element can be between 5ppm and 20ppm. Phosphorus can promote stem growth, so it is necessary to limit its application to prevent plant overgrowth. Before sowing, fertilizers containing perphosphate can be added to the substrate, and liquid fertilizers containing phosphorus can also be applied, such as ammonia phosphate, potassium phosphate, 20 Mel, 10 Mel, 20, 15 Mel, 5 Mel, 25, etc. Note that when calculating the content of phosphorus, the content on the bag is the amount of P2O5, and the content of phosphorus can be multiplied by 0.437.

Potassium (K): potassium is the catalyst of metabolism, which enables stomata to perform its function normally and improve disease resistance. Potassium deficiency plants will appear lower leaf edge necrosis, stem and petiole weak; too much potassium will reduce the absorption of calcium, magnesium, manganese, zinc and ammonia nitrogen. The normal concentration of potassium is from 150ppm to 250ppm. In order to avoid that potassium does not affect the absorption of calcium and magnesium by plants, the proportion of K:Ca:Mg in fertilizer can be controlled at 4:2:1 (similar to poinsettia). The better sources of potassium are potassium nitrate, 20 Mel 10 Mel 20 or 15 Mel 5 Mel 25 fertilizers. Keep in mind that when calculating the fertilization ratio, the content on the bag refers to the percentage of K2O, so the potassium content needs to be multiplied by the parameter 0.83.

Calcium (Ca): calcium is the main component of cell wall. The main symptom of plant calcium deficiency is blackening and necrosis of stem and root growth point. Calcium is an immovable element in plants and is absorbed by root tips. Excessive calcium will reduce the absorption of potassium, magnesium and boron by plants. It is suggested that the concentration of calcium fertilizer is from 50ppm to 100ppm, and the proportion of K:Ca:Mg in fertilizer is 4:2:1. Irrigation water (if the content of calcium is high), lime containing dolomite, and calcium nitrate can also provide calcium.

Magnesium (Mg): magnesium plays an important role in the molecular composition of chlorophyll and the activation of enzymes. The symptoms of magnesium deficiency in the plant are that the veins of the old leaves are green and the leaves may curl upward; too much magnesium will reduce the absorption of calcium by the plant. The concentration of 25ppm to 50ppm is fine. Note that the proportion of K:Ca:Mg in the fertilizer is 4:2:1. Lime and magnesium sulfate containing dolomite can be used as magnesium sources. In order to correct magnesium deficiency, magnesium sulfate solution can be used to irrigate the root. Be careful not to mix it with other fertilizers and apply it once a month to prevent the occurrence of magnesium deficiency.

Iron (Fe): like magnesium, iron plays an important role in the formation of chlorophyll. The symptom of iron deficiency in the plant is that the veins of the new leaves are green and the apex is necrotic in severe cases. Iron deficiency will occur when the pH value of soil matrix is too high, root necrosis or the content of phosphorus, manganese and copper is too high. Too high iron content will lead to insufficient absorption of manganese by plants, and when the pH value of the substrate is too low (pH7.0), the availability of iron will decrease, which will lead to iron deficiency (iron deficiency chlorosis), so it is necessary to detect the pH value and alkalinity of irrigation water and inject acid into the irrigation water if necessary.