Potassium fertilization of sugar beet
Sugar beet is a plant of great economic importance in Poland. In recent years, average sugar beet yields have increased significantly, but they are lower than in the EU, which is mainly due to underestimating of potassium fertilization.
Potassium takes part in the formation of carbohydrates. It increases the photosynthesis efficiency in leaves and the rate of sucrose transportation to roots. A good potassium nutrition also improves the use of nitrogen by sugar beet. Potassium plays a role in regulation of water management in plants. Thanks to this, plants well-fed with potassium are more resistant to water shortages and more easily withstand periodic droughts, more and more frequently occurring in Poland. Potassium deficiency increases the level of infestation by pathogens, regardless of the level of nitrogen nutrition. Potassium also increases the resistance of beetroot plants to aphids and beetroot nematodes.
Potassium deficiency in beet is manifested by dark green with a bluish shade of leaves. At the tops and edges of the lower leaves, a yellowish green band appears, gradually covering the entire lamella, which dies prematurely, taking on a brown and dark brown colour.
The potassium content of the soil should be at least at medium level. Potassium fertilization has a positive effect on the root yield. If the potassium content of the soil is very low, the application of potassium salt may increase the root yield by 25%. At the same time, the sugar content increases. Application of potassium causes reduction of roots’ content of Alpha-Amino nitrogen which is a very harmful molasses-forming element. The result of such potassium performance is an increase in the technological yield of sugar by 21%.
Sugar beet is an exceptionally potassium-loving plant. For the production of 1 tonne of roots with an appropriate weight of leaves, sugar beet plants have to uptake from 6 to 9 kg of potassium (K2O). This means that at a yield of 60 t/ha beet should absorb as much as 360-540 kg K2O/ha. The dose of potassium must be adapted to the abundance of soil in the available forms of this component.With a very low potassium content in the soil, the doses range from 350 kg K2O/ha on heavy soil to 400 kg K2O/ha on medium soil.
Sugar beet fertilization for root yield ≥ 50 t/ha
|
Nutrient content | Doses N [kg/ha] | Doses P2O5 [kg/ha] | Doses K2O [kg/ha] | |
|---|---|---|---|---|
| medium soil | heavy soil | |||
| Very low | 120-140 | 100-120 | 400 | 350 |
| Low | 90-120 | 80-100 | 300-400 | 250-350 |
| Medium | 60-90 | 60-80 | 200-300 | 150-250 |
| High | 30-60 | 40-60 | 100-200 | 50-150 |
| Very high | 30 | 20-40 | 50-100 | <50 |
When the farmer does not know the soil’s abundance of available phosphorus and potassium, fertilizer doses can determined indicatively on the basis of the N:P:K ratio. For sugar beet fertilization they amount to 1:0,8:1,2.
Sugar beet plants react very well to the chloride form of potassium fertilizers, because they are chloro-loving. Therefore, for most farms the best fertilizer is high K2O content potassium salt (60% K2O). On the soils with low potassium content, it is best to apply potassium fertilizers in increased doses 2 years before beet cultivation, under forecrop.
On the soils with at least medium abundance of potassium it is enough to do it under the forecrop, or ultimately after harvesting the forecrop and before winter ploughing. The spring application of potassium fertilizers is less advantageous, because it does not allow sufficient mixing with the soil during pre-sowing cultivation.
Written by dr inż. Arkadiusz Artyszak