Fruit plants
Under conditions of good potassium supply to plants, the fruit is better coloured, more firm, has a better taste and has better storing ability. Plants optimally nourished with potassium are more resistant to low temperatures in winter. With a potassium deficit, the fruit yields are significantly lower and the tree shoots are short and thin.
Although the nutritional requirements of most fruit trees are lower than those of field crops, their fertilizer system needs to be carefully planned in order to achieve high quality yields. Mature trees planted in dense spacing, depending on soil and climatic conditions and the agrotechnology used, take 50-120 kg N, 5-20 kg P205 and 60-150 kg K20 per hectare per annum. 40-60% of nitrogen and 40-70% of potassium and phosphorus out of above mentioned quantities are taken out of the field in yield and remain in the woody parts of the trees. After application of the optimal recommended NPK doses before the planting of trees, the fertilization of fruit plants may be unnecessary within the next 2-4 years. Due to the fact that most potassium is accumulated in fruit, 50-120 kg K20/ha (about 80-200 kg of potassium salt per 1 ha) should be applied every year in the fruit bearing orchard. The dose of potassium depends to a large extent on the rootstock used, the variety and age of plants and climatic conditions. According to the recommendations of the Institute of Pomology and Floriculture in Skierniewice (2009), depending on the content of nutrients in the soil, the doses of phosphorus and potassium are within the limits given in Table 1.
Phosphorus and potassium fertilization on fruit plantations, kg/ha
| Specification | P2O5 | K2O | ||||
|---|---|---|---|---|---|---|
| Nutrient availability class | Nutrient availability class | |||||
| low | medium | high | low | medium | high | |
| prior to starting up plant nursery | 50-70 | 30-50 | 10-20* | 70-90 | 50-70 | - |
| prior to starting up orchard | 300 | 100-200 | 50-100* | 150-300 | 100-200 | 20-40** |
| orchard giving fruits | 80-120 | 50-80 | 20-40** | |||
* - on soils where phosphorus fertilizers were not applied for at least 6-8 years
** - on heavy soils
The dose of nitrogen is dependent on the content of organic matter concentrating nitrogen.
Doses of nitrogen application in orchards, kg N/ha
| Specification | Organic matter content in soil (%) | ||
|---|---|---|---|
| 0,5-1,5 | 1,6-2,5 | 2,6-3,5 | |
| Plant nursery - 1st year | 80-100 | 60-80 | 40-60 |
| Following years | 60-80 | 40-60 | 20-40 |
| Orchards - first 3 years | 15-20* | 10-15* | 5-10* |
| Following years | 60-80 | 40-60 | 20-40 |
* - N dose in g/m2
Plants well supplied in potassium fruits have better colour, are firmer, taste better and are better for storing. Plants optimally nourished with potassium are more resistant to low temperatures in winter. Deficiency of K leads to considerably lower fruit yield and shoots are short and thin.