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Fertilizing winter oilseed rape - how to do it right?

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Winter rapeseed is an oil plant of great economic importance. Its crops in Poland occupy 95 percent of all oilseed crops area. This is why we chose fertilization of winter oilseed rape as the topic of our next article.

Locations rich in humus and calcium classes I-III show the highest efficiency for cultivation. Class IV soils have a worse yield. Rapeseed likes high air humidity, and preferably stands with a total rainfall of more than 520 mm. It sprouts after 7 days. It is a plant with a strong, pile-like root system, which can reach 50-60 cm in autumn, and 120-290 cm in full vegetation. Oilseed rape needs 65-80 days with an average temperature above 5°C to develop properly in autumn. Important elements in the initial stage of winter oilseed rape cultivation are:

Additionally, you should remember about fertilizing winter rapeseed, which we write about later in this article.

Winter oilseed rape and its needs

Winter oilseed rape is a plant that requires very large amounts of nutrients, i.e. intensive and proper fertilization. The basis is to provide the plant with properly balanced and selected ingredients - foreground, background and microelements. Only such comprehensive fertilization of winter oilseed rape gives a chance to achieve the optimal course of vegetation and, as a result, to obtain a yield of the assumed size and quality.

Assuming the average soil fertility, the nutritional demand of rapeseed to produce 1 t of seeds and the appropriate weight of straw and roots is as follows:

Nitrogen (N) - 50 - 60 kg, Phosphorus (P2O5) - 25 - 30 kg, Potassium (K2O) - 60 - 70 kg, Calcium (CaO) - 39 - 70 kg, Magnesium (MgO) - 6 - 11 kg, Sulfur (S) - 18 - 22 kg, Boron (B) - 60 - 120 g, Copper (Cu) - 10 - 40 g, Iron (Fe) - 260 g, Manganese (Mn) - 50 - 100 g, Zinc (Zn ) - 160 - 180 g, Molybdenum (Mo) - 1 - 2 g.

The key parameter is the appropriate soil pH, which in this case should be 6.0 - 7.0 and the fact that rapeseed grows badly on soils poor in magnesium.

Rapeseed and fertilization - how to fertilize winter oilseed rape?

In this case, it is recommended to fertilize winter oilseed rape with well-absorbed (soluble) forms of phosphorus and potassium, using complex fertilizers used for stubble or for sowing. The use of nitrate nitrogen should be avoided as it reduces the frost resistance of rape. In autumn, the average demand for rape with a yield of 4 - 5 t/ha is: nitrogen - 60 - 80 kg, phosphorus - 80 - 110 kg, potassium - 140 - 180 kg. In practice, in rape crops, all the required phosphorus is supplied in autumn, while potassium is divided into 2 autumn doses of 50% or in doses of 75 and 25%. Phosphorus at this time is responsible for building the foundation of the future crop, that is, the development of the root system. Potassium thickens the cell sap (increases frost resistance), regulates the water balance in the plant and creates a leaf rosette. When determining specific doses of fertilization, the soil abundance in individual components (soil tests), introducing components from harvest residues or organic fertilizers (manure, slurry, liquid manure) should of course be taken into account.

A properly developed oilseed rape should have 8 - 12 leaves in autumn, an unraised and thick (1 - 2 cm) root neck, and a sufficiently deep and pile-like root system. In fact, already in autumn, rape produces branching buds of side shoots - from the 5 - 6 leaf stage and inflorescence formation - from the 8 leaf stage.

As important as the soil fertilization of winter oilseed rape is the supply of nutrients through the leaves. This method of supplying micronutrients to the plant is many times more effective than the soil fertilization of rape, and additionally allows for faster supplementation of the necessary ingredients. In the case of macronutrients, it may be a supplementary treatment to soil fertilization, especially in the event of unfavorable weather conditions (low temperatures, water shortages). It is also worth recalling that the root system is not always efficient enough to provide a sufficient amount of nutrients, especially in critical phases of plant growth. In the cultivation of oilseed rape in the autumn, it is advantageous to use a foliar supply of plants with sulfur and magnesium.

Rapeseed foliar fertilization

In the case of micronutrients, foliar feeding of oilseed rape should be considered as basic, because in this way all the micronutrient needs of the plant can be covered. It should be remembered that the use of micronutrients is treated as a preventive treatment. Waiting for signs of deficiencies - often difficult to diagnose - and performing the treatment interventions, in each case results in a certain decrease in yield. Foliar fertilization of oilseed rape should start in autumn at the 6-8 leaf stage. Extensive research in this area and practice show that oilseed rape should be fertilized with boron (low level in 80% of soils in Poland), manganese, copper, molybdenum, zinc and iron. The legitimacy of the use of microelements already at the stage of autumn treatments justifies their influence on a number of important processes taking place in this period.

Boron - is responsible for saturating rapeseed roots with sugar, which increases winter hardiness. It influences the development of generative organs and stimulates the overwintering processes. Deficiency symptoms include empty space in the root under the growth cone and fringe reddening of the leaves.

Manganese - intensifies the photosynthesis process, lowers the level of auxins (which results in growth inhibition and preparation for resting period), has an impact on the proper uptake of phosphorus and, consequently, the development of the root system. The symptoms of deficiencies include marbling of leaves.

Molybdenum - is responsible for the proper transformation of nitrogen - improvement of winter hardiness.

Copper and Zinc - regulate the hormonal balance - resistance to diseases.

Iron - is responsible for building tissues.

As a result of using a micronutrient fertilizer with a rich composition, we can obtain a very wide spectrum of action, namely: increasing the chances of overwintering, intensifying the development of individual parts of the plant, improving disease resistance, proper metabolism and nutrient uptake.

In order to take full advantage of the effectiveness of such treatment, an appropriately balanced and well-absorbed foliar fertilizer should be selected, suitable for simultaneous use with fungicides and inecticides.

Fertilization of rape in spring - starting dose for rape

With the beginning of the spring season, winter oilseed rape should be fertilized primarily with nitrogen, sulfur and micronutrients, and supplemented with magnesium, potassium and phosphorus. Soil fertilization of rape with sulfur should be carried out before the start of spring vegetation (early spring), because sulfur is one of the most important ingredients influencing nitrogen absorption. In practice, sulfur fertilization is most often performed together with other ingredients, i.e. nitrogen, magnet and potassium. First, we apply macronutrients, often on still frozen soil - in the absence of snow cover.

We supply micronutrients for plants in the foliar form. For this reason, their application occurs later, after the plants have at least partially restored the assimilation apparatus. The higher ambient temperature is also important here, since the physiological activity of the plant is required for the effective application of foliar fertilizer to rape. In practice, it is assumed that in spring it is an average temperature of 5-10 degrees Celsius. An important factor influencing the proper performance of rape fertilization from early spring is the evaluation of the yield potential of crops. This potential is the result of several factors, such as: the condition of plants in the autumn growing season, the course of winter, soil quality and the prevailing weather conditions. The experience of previous years indicates a tendency towards a long autumn vegetation of rape, which means that larger and better developed plants show increased nutritional needs. In the case of too low supply from the soil, plants show deficiencies, which results in slower regeneration and poor growth. In this situation, it is crucial that nitrogen and other nutrients are given to the plant as early as possible. There is a saying that "nitrogen should wait for the rapeseed", but the timing must be right, as stimulating the plants with nitrogen before the spring frosts return can damage plants.

Fertilization of winter rapeseed with nitrogen

Fertilizing oilseed rape with nitrogen has a strong influence on the yielding effects of plants. The required spring nitrogen dose is the product of the assumed yield (t/ha) and the unit nitrogen uptake (kg/N) for the production (1 t) of seeds together with the appropriate weight of straw and roots, after subtracting the assumed existing nitrogen content in the soil.

After determining the fertilization needs, the next stage of the procedure is to divide the dose, the date of application and the type of fertilizer (nitrogen forms). As previously mentioned, the first dose of nitrogen should be given as soon as possible, while the second should be given 2-4 weeks apart, but not later than 4 weeks before flowering. In practice, this means that if we give the first dose of nitrogen in early March, we will try to use the second dose in the middle of this month. In the case of intensive nitrogen fertilization, three doses should be applied, oscillating between - 60%, 30% and 10%.

Delayed nitrogen fertilization increases the susceptibility of plants to lodging, causes later and long-lasting flowering, as well as excessive vegetative development. As a consequence, the flowers are less pollinated and the pods develop worse, leading to a deterioration of the yield and difficult harvesting. Under certain conditions, eg prolonged winter or anticipated long-term drought, it is possible to use nitrogen in one - increased - dose. It will bring much less losses than late application or application in conditions where the fertilizer will not work.

The selection of the form of nitrogen in the fertilizer used is equally important. This is especially true for the first dose and it is advisable that at least a significant part of it should be an easily accessible form of nitrate (NO3), which enables faster regeneration and reconstruction of the leaf rosette.

Application of foliar fertilizers is performed in spring in two standard treatments. It is important to use a fertilizer that corresponds to the composition of the current nutritional needs of plants. The key micronutrients that should be supplied to rapeseed from the beginning of spring vegetation are boron, manganese, molybdenum, copper, zinc and iron. The first one should be performed in the rosette phase, i.e. 8-10 leaves, the second in the budding phase. During this period, there is a rapid increase in plant mass, which causes a very high demand for nutrients. The supply of key micronutrients has a direct impact on the proper course of vegetation, resistance to pathogens, yield and seed quality, and regulates many processes related to metabolism during the period of intensive spring growing.

Boron - significantly influences pollination and fertilization, improves the process of flower formation, thus increasing the number of pods and seeds, supports the growth of root cells and the uptake of potassium. It regulates the water balance, improves transpiration and respiration. Deficiency reduces inflorescences, the number of pods and seeds, increases susceptibility to diseases, reduces frost resistance and causes stem cracking.

Manganese - is responsible for the synthesis of chlorophyll and carbohydrates and for stimulating the growth of new cells. It has a positive effect on the expansion of lateral roots, improves their health, and stimulates the uptake of phosphorus and iron from the soil. Deficiency results in stunted growth, susceptibility to disease, reduced number of pods and less oily seeds.

Iron - is responsible for the synthesis of chlorophyll, carotene and lignin, affects the number of ribosomes, and therefore takes part directly in the process of protein synthesis

The complex of copper (Cu), zinc (Zn), molybdenum (Mo), boron (B), manganese (Mn) and iron (Fe) as well as amino acids and vitamins, significantly improves the transport of nutrients in the plant, increases the possibility of taking and using nutrients from soil, improves resistance to stress conditions (drought, excess water, frost, pest attacks), increases the concentration of chlorophyll, leading to a higher degree of photosynthesis.

It should be remembered that the key factor influencing the effectiveness and quality of the micronutrient fertilization of rapeseed is an appropriately high concentration of nutrients and the possibility of their absorption by the plant (penetration through the cuticles). The possibility of using them together with insecticide protection or fungicides gives very good results.

The lack of availability of any macro or micronutrients results in the appearance of characteristic symptoms. Usually, it is difficult to say unequivocally which component is missing, because it can often be more than one element at the same time. Sometimes the occurrence of a deficiency does not produce visible effects, and we find out about it at the time of harvest, after a reduction in the yield is found.

Characteristic symptoms of nutrient deficiency for winter oilseed rape

Nitrogen - slower growth, underdeveloped root system, yellowing of leaves, shortening of shoots, accelerated maturation.

Phosphorus - purple discoloration, leaves turn blue, slower growth, poor flower and seed setting, shortening of shoots.

Potassium - yellowing of the edges of the leaf blade, poorly developed shoots, poor flowering and ripening.

Magnesium - bright purple leaves between veins, thin leaf blade.

Calcium - necrosis of leaf edges, small leaves, poor flowering and pod formation, stunted growth and browning of roots.

Sulfur - young leaves take a boat-like shape, the leaf blade turns purple, flowers are light yellow turning into white, weak binding of pods and seeds.

Boron - browning of the root, dieback of the growth cone, "corkiness" of the shell, poorly formed seeds, fine seeds and browning seeds before maturation.

Manganese - stunting, chlorotic discoloration on plants.

Copper - leaves elongated, whitened, dieback of the growth cone.

Zinc - weak flower and seed setting, small leaves with light spots.

Molybdenum - yellowing and dieback of leaf buds, death of growth cones, deformation and yellowing of leaves.

Iron - green leaf veins, leaf yellowing all over.

In order to prevent possible shortages, winter oilseed rape should be fertilized. If you are interested in DR GREEN fertilizers, please contact us or visit our online store with fertilizers!

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