Potassium fertilization of cereals
Poland is a significant producer of cereal grain in the European Union, the world's largest producer of triticale and the second largest producer of rye. However compared to other European countries, yields of cereals obtained in Poland are much lower.
Yield-forming function of potassium
In addition to nitrogen, potassium is absorbed by the plants in the largest quantities. With the yields of cereals in Poland, the uptake of potassium on a 1 ha field varies from just over 88 kg to about 114.5 kg K2O on good rye soils and from about 113 kg to 148 kg K2O on very good wheat soils. This means that the doses of potassium fertilizers applied in Poland are usually too small to satisfy the nutritional needs of plants.
Potassium takes part in the water management of plants and in the process of plant growth. Potassium activates enzymes, takes part in basic biochemical processes, in the transport of mineral and organic compounds in plants. In addition, potassium directly and indirectly increases winter resistance. What is also important is the contribution of potassium to the metabolism of nitrogen compounds in the plant. Insufficient supply of potassium in plants promotes the accumulation of simple nitrogen compounds in plants: nitrates, amines and other nonprotein nitrogen compounds, reducing the quality of yield.
Effect of potassium on yields
In the conditions of deficiency of potassium forms available for plants in the soil, the application of potassium results in a significant increase in cereal yields. Application of optimal potassium dose on soils with low content of this nutrient may cause an increase in rye grain yield of 0.2 t, over 0.3 t of wheat and oat grain and 0.6 t of barley grain. It is believed that the optimum soil potassium content is medium (class III), which enables farmers both to obtain expected crop yields and to apply with fertilizers the same amount of nutrient as was elevated with the crop yield.
On soils with a lower than medium abundance in potassium, the doses of potassium fertilizers shall be appropriately increased in order to improve the growth conditions and plant nutrition.
Doses of potassium fertilizers for basic cereal crops on arable land
|
Cereals | Soil suitability complex | Potassium doses (kg K2O/ha) | ||||
|---|---|---|---|---|---|---|
| Soil abundance | ||||||
| very low | low | medium | high | very high | ||
| Witner wheat | 1, 2, 10 | 110 | 90 | 75 | 65 | 20 |
| | 3, 4, 8, 11 | 100 | 80 | 65 | 55 | 20 |
| | 5 | 80 | 70 | 60 | 50 | 20 |
| Rye | 1, 2, 10 | 125 | 100 | 85 | 70 | 30 |
| | 3, 4, 8 | 115 | 90 | 75 | 60 | 30 |
| | 5 | 115 | 90 | 75 | 60 | 30 |
| | 6, 9 | 85 | 70 | 55 | 45 | – |
| Triticale | 1, 2, 10 | 100 | 85 | 80 | 65 | 25 |
| | 3, 4, 8, 11 | 100 | 80 | 65 | 55 | 20 |
| | 5, 6, 9 | 95 | 80 | 70 | 60 | 30 |
| Spring barley | 1, 2, 10 | 90 | 75 | 60 | 50 | – |
| | 3, 4, 8, 11 | 85 | 60 | 50 | 35 | – |
| | 5 | 85 | 85 | 70 | 55 | 15 |
Cereals can be successfully fertilized with potassium chloride fertilizers with high potassium concentration (e.g. potassium salt 60%). The optimal timing for the application of potassium fertilizers is the pre-sowing period. Potassium cation is well sorbed by the solid phase of the soil, which limits its leaching. For this reason, potassium fertilizers can be used in the autumn. On light and very light soils however there is a risk of washing out of potassium applied in autumn for spring cereals. Therefore, in order to reduce potassium losses, it is possible to apply this fertilizer in early spring.
Written by Dr Tomasz Sosulski