by Cucumbers have high requirements for soil fertility, as well as humidity and temperature conditions. But it is not always possible to create suitable conditions for this crop. And sometimes we notice that cucumbers develop slowly, the leaves turn yellow at the edges, and the ovaries fall off.
To grow cucumbers, gardeners try to select a plot with the best and most fertile soil, since this heat-loving plant develops well and bears fruit abundantly only on light, loose soil with a large amount of organic matter. Cucumber does not tolerate a high concentration of mineral salts in the soil – therefore, you need to be very responsible when fertilizing the crop and select fertilizer, taking into account the signs of a lack of a particular nutrient.
What cucumbers lack
During the flowering and fruiting period, cucumbers consume a lot of nutrients. And they especially need a sufficient amount of nitrogen, potassium and calcium. Potassium plays an important role in the process of photosynthesis, affects the taste of fruits. Calcium is involved in the formation and division of cells, regulates water balance, ensures the full development of the root system. In addition, both potassium and calcium increase plant resistance to various diseases.
With a lack of potassium, the lower leaves of the cucumber begin to turn yellow at the edges. Later, the tips and edges of the leaves begin to die off (marginal “burn” of the leaves). The leaf blades are deformed, twisted, the veins seem to be immersed in the leaf tissue. A lack of potassium usually causes a delay in growth and formation of ovaries, and later often leads to the appearance of curved and bitter fruits.
If a yellow border appears on the upper, young leaves, this indicates a calcium deficiency. With a strong deficiency, plants lag in growth, the apical points of the bushes begin to die off, and apical rot of the fruits appears, since calcium first enters the lower leaves, and then the upper part of the plant and the fruits.
Why Nutrients Are Not Absorbed
Even if you have carefully prepared the bed for planting cucumbers, limed the soil, some macronutrients may still be unavailable for absorption by the root system. Why does this happen? There are several reasons for this:
- Lack of moisture. If watered irregularly, cucumbers develop poorly, the root system does not absorb nutrients from the soil, and the fruits of some varieties may taste bitter, since they accumulate the bitter substance cucurbitacin. Cucumbers need to be watered as the soil dries out, moistening the soil to the depth of the root layer, that is, 20-25 cm. For watering, only warm water should be used, the temperature of which is 20-22 ° C. In cold or cloudy weather, watering should be limited to prevent the development of root rot.
- Sandy soil. On sandy loams, cucumbers often suffer from a lack of moisture and nutrition, since nitrogen and potassium are quickly washed out into the lower layers of the soil with constant watering. Therefore, if the soil on your site is sandy or sandy loam, then you need to water and feed cucumbers more often.
- Low or high temperature. The optimum temperature for cucumber development is 20-25°C during the day and 16-18°C at night. At temperatures below 12°C, the cucumber root system loses the ability to absorb water and nutrients from the soil – therefore, 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, and their transpiration is disrupted. In this regard, fertilizers should be applied at an air temperature of no higher than 25°C, for example, in the morning or evening.
- Unbalanced feeding. Calcium and potassium are antagonist elements. With excessive application of potassium fertilizers, calcium is poorly absorbed and vice versa: after liming the soil, potassium starvation is often observed. Boron and nitrogen in nitrate form promote the absorption of calcium and its movement through plant tissues, and excess magnesium, ammonium nitrogen, potassium reduce the availability of calcium. Therefore, it is very important to apply fertilizers that are balanced in composition and, if necessary, carry out foliar feeding.
How to feed cucumbers to save the harvest
The lack of nutrients can be eliminated by root and foliar feeding. But before applying fertilizers, you need to take a close look at the plants and understand what the cucumbers lack – potassium or calcium.
To quickly stop calcium starvation and yellowing of the upper leaves of cucumbers, foliar feeding with complex fertilizers will help: Brexil Sa, AgroBor Sa and KalMagBor+ME, Kalcifol 25. If there is not enough nitrogen in the soil and cucumbers do not grow fat, then calcium nitrate can be used as a fertilizer, which is suitable for both root and foliar feeding, especially in the first half of the growing season.
To prevent calcium deficiency in the future, dolomite flour, chalk, and lime can be added to the soil in the fall. However, before you start liming the soil, you should check its acidity so as not to make a mistake with the rate of application of lime fertilizers.
To cope with potassium deficiency of cucumbers during the fruiting period, root feeding with a solution of mineral fertilizer with an increased potassium content will help. For this, you can use potassium sulfate (20 g per 10 l of water), potassium nitrate (15 g per 10 l of water), as well as complex fertilizers with microelements: Kristalon orange, Kristalon green (cucumber), AgroMaster 15.3.38 + 4, Agricola for cucumbers, zucchini, squash, etc.
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.
In addition, wood ash is an excellent source of potassium, calcium and other nutrients. This universal fertilizer can be used in the form of an infusion throughout the entire fruiting period of cucumbers. To prepare an ash infusion and ensure effective absorption of potassium, pour 1,5 cups of ash into 10 liters of warm water and leave for several hours. Then add 1 teaspoon of citric acid to the solution, mix thoroughly and feed the cucumbers, using 1 liter of infusion per bush.
In addition to potassium, cucumbers need nitrogen throughout the season, which is best applied in the form of organic fertilizers. As fertilizer, you can use an infusion of weeds (nettle, dandelion, goutweed, clover, horsetail), an infusion of mullein, biohumus, as well as fermented “tea”, i.e. an infusion of rotted grass. Such fertilizers allow you to extend the period of active fruiting of cucumbers, stimulate the development of young shoots and the formation of new ovaries.
To avoid imbalance of macro- and microelements during the growing season of cucumbers, try to maintain crop rotation, maintain soil fertility: sow green manure after harvesting, apply organic fertilizers when preparing the bed. Do not forget about the simple rule: how much harvest we have collected, so many nutrients we must return to the soil.
It is not always easy to determine the lack of a particular nutrient. Sometimes the signs of deficiency are not clearly expressed, and they can be mistaken for the beginning of some disease. Therefore, inspect the plantings as often as possible in order to fertilize or treat the plants in time.
