by The condition of the cucumber leaves and fruits can tell you what nutrients the plant lacks. If you notice that the edges of the cucumber leaves have turned yellow, this indicates an unbalanced diet and, most often, a potassium deficiency. How can you eliminate this problem and prevent it from occurring in the future?
Cucumbers have a relatively short growing season and quickly enter the fruiting phase. During the ripening of the fruit, the plants consume a large amount of nutrients, but especially a lot of potassium. This macronutrient plays an important role in the formation of carbohydrates and cell division, increases the resistance of plants to diseases and adverse environmental conditions, and affects the taste of the fruit.
It is precisely with a lack of potassium that a pale yellow border first appears along the edges of the leaves, which becomes brighter over time. With acute potassium deficiency, the fruits acquire a pear-shaped form, can taste bitter, the leaves become covered with brown spots, and the border along the edges of the leaf blades becomes brown and begins to crumble, that is, the so-called “marginal leaf burn” appears. The lower leaves suffer first, as they are older.
Cucumber leaves dry out and turn white, starting from the edge, also with a calcium deficiency. However, this first appears on young leaves: they not only become lighter, but also deform, then the growth point dies, and the stems become woody. With a calcium deficiency, the lower leaves remain green.
How to Prevent and Treat Potassium Deficiency
Since cucumbers grow well and bear fruit only in fertile soil, when preparing the bed, add not only organic fertilizers (biohumus, compost, humus), but also mineral fertilizers that contain essential macro- and microelements in an accessible form (Rodnichok, Biofertilizer Vegetables, OMU Universal, AVA Universal, etc.).
During the fruiting period, fertilize with potassium fertilizer every two weeks: potassium sulfate (15 g per 10 l of water, 0,5 l per bush), potassium monophosphate (10 g per 10 l of water, 0,5 l per bush) or a complex fertilizer with a high content of phosphorus and potassium (Kristalon Orange, AgroMaster 3.11.38+4, Agricola for cucumbers, zucchini, squash, etc.). If the soil on the site is acidic or slightly acidic (pH lower than 6,7), carry out 2-3 root fertilizing of cucumbers with ash infusion (150 g per 10 l of water, 1 l per bush).
Apply root fertilizer to cucumbers only after watering. Try to alternate root and foliar fertilizers, mineral and organic. Adjust the amount of fertilizer applied depending on the condition of the plants and the manufacturer’s recommendations.
Frequent fertilizing with small doses of various potassium fertilizers is better than a single application of potassium in large quantities, since when potassium is present in excess in the soil, it turns into inaccessible forms and prevents the absorption of magnesium, calcium, ammonium nitrogen, manganese and some other elements.
Why is potassium poorly absorbed?
Even if you applied the required amount of potassium or complex fertilizers when planting, this does not mean that the plants will necessarily receive adequate nutrition. For example, potassium, like nitrogen, is a fairly mobile element and can simply be washed out of the soil, especially if your site has sandy loam, sandy or peaty soil. But there are other reasons for poor potassium absorption:
- Low or very high temperature. The optimum temperature for cucumber development is 20-25°C during the day and 16-18°C at night. However, it is not always possible to create such ideal conditions. At temperatures below 12°C, the cucumber root system loses the ability to absorb water and nutrients from the soil, so on cold days it is advisable to carry out only foliar feeding. And in the heat, when the soil overheats, many nutrients also become unavailable. In this regard, fertilizers should be applied at an air temperature of no higher than 25°C, for example, in the morning or evening.
- Excessive calcium in the soilWhen calcium is added in excess (for example, during deoxidation or liming of the soil), potassium is bound and is not absorbed by the root system of plants, since potassium and calcium are antagonist elements.
- Irregular watering. Cucumbers, as is known, are a moisture-loving crop. Therefore, it is necessary to water the plantings regularly, as the soil dries out, using warm water at a temperature of 23-25 ° C. In order for mineral substances from the soil to be well absorbed, the soil in the root zone should always be moderately moist, especially during the fruiting period. However, excessive watering of cucumbers should be avoided, since this leads to the leaching of essential nutrients and the appearance of root and root rot.
To protect the soil from temperature fluctuations and retain moisture in the root zone, it is advisable to mulch the bed with hay, straw, rotted sawdust or other material. Mulching will help to facilitate the care of the plantings and reduce the frequency of watering.
As a result of the lack of any macronutrient, the yield of cucumbers and the nutritional value of the fruit decrease. In addition, inadequate nutrition leads to the fact that the bushes as a whole develop poorly and lose the ability to resist diseases. Therefore, try to look at your plants more often so as not to miss the beginning of the problem and solve it in a timely manner.
