- Does it make sense to apply NPK fertilizers as a top dressing?
- What is the mobility of phosphorus?
Phosphorus is needed right from the start, the top dressing will not have time to move
If the fertilizer has not been applied yet, because, for example, it has not reached the farm, and the rape has been sown, then we can say that there is no way out – the multi-ingredient must be applied top dressing. But we must also remember that the effectiveness of such an application is much lower than pre-sowing fertilization. In this context, special attention must be paid to phosphorus. While potassium is applied top dressing during vegetation, both in late autumn and before the resumption of spring vegetation, the justification for such an application of phosphorus is unfortunately small.
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When to plow for winter cereals?
First of all, phosphorus is a component with low mobility, its movement in the soil profile is very small. Hanging it with the soil allows for such movement of this macroelement so that it gets to the zone in which it is needed – and let us note that its special usefulness is related, among other things, to the starting period after sowing, because it affects the development of the root system. Of course, it is also needed in later afzcah (depending on the plant), although even then it must be properly moved. If we take into account the low mobility of phosphorus, we will notice that when it is applied top dressing, without mixing it with the soil, it will remain in the top layer of the soil. This is very unfavorable, because this layer is susceptible to drying, and therefore the solubility of P will be minimal. In addition, we will not offer the component to the root system in this way.
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The capitation application is a lifeline
Phosphorus movement is much slower than potassium. The best absorption of the element is observed in the root zone, and it is only from there that it can be absorbed by plants, also in later development stages. Meanwhile, the daily movement of phosphorus in the soil profile is much less than 1 mm per day (up to 0.4 mm per day in favourable conditions). Therefore, any later phosphorus deficiencies should be supplemented through foliar application. Although this way we will not satisfy the nutritional needs of the plant, we will ensure quick absorption. However, if it is necessary to fertilise after top dressing, it is of course possible – and even necessary – but only in very good moisture conditions. Phosphorus supplied in this way will no longer be able to participate in the initial development of the root system, but over time – in good moisture conditions – it is able to reach the zone from which it will be taken. Nevertheless, this is an emergency solution. Pre-sowing application and mixing the fertiliser with the soil will always be a better solution.
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How quickly does rapeseed sprout?
