Botanical and biological features
The cucumber (Cucumis sativus L.) is an annual herbaceous plant belonging to the Cucurbitaceae family. The root is a tap one and branching. The bulk of the roots are located in the arable layer. Under favorable conditions, the emergence occurs 4-6 days after sowing. The stem length and the number of side shoots vary greatly according to the variety and growing conditions.
Cucumber is a very heat-loving plant. The optimum germination temperature is 25–30˚С, and the optimum growth temperature is 25–28˚С. Germination occurs at temperatures not lower than 15–16˚С. Cucumber plants can die even at temperatures as high as 5–7˚С if they are exposed to these temperatures for a long period time.
Cucumber has moderate requirements for light conditions – lower than those of tomato, pepper and eggplant. However, low light conditions, which occur in greenhouse cultivation, tend to result in drawn plants and lower yields.
Cucumber is a moisture-loving plant. The optimum soil moisture content for adequate cucumber growth and fruiting is 80–85% of field moisture capacity and the relative air humidity is 90%. High requirements of cucumber for soil and air humidity are due to its poorly developed root system characterized by low absorbing capacity and to its bulky and vigorous above-ground portion which evaporates large quantities of water.
In crop rotation, cucumber normally follows winter wheat, peas, potato, onion and cabbage. Sowing is performed when the soil at the seeding depth (4–5 cm) has warmed up to 15˚С. At lower temperatures, the seeds get mouldy. The planting pattern is 120–150 х 30 cm (2–2,5 pl/m2) with vertical culture and 120+30 х 25–30 cm (4,5–5 pl/m2) with horizontal culture. The seeding rate is 1,5–3 g per 10 m2 (1,5–3 kg/ha).
Cucumber is characterized by high depletion of soil nutrients, particularly potassium and nitrogen. The crop responds very well to high rates of fresh manure application: up to 80–100 kg per 10 m2 (80–100 ton/ha). In addition to manure, mineral fertilizers (nitroammophoska) should be applied at a rate of 700 g per 10 m2 (N 110, P2O5 110, K2O 110 kg of active substance per hectare) with autumn soil cultivation. During the growing season, regular applications of potassium nitrate are made at rate of 400–500 g per 10 m2. Good results have been achieved when fertigating cucumber with Terraflex C (17-7-21+3MgO+МЕ). Magnesium sulfate is applied at a rate of 300–600 g per 10 m2 (Mg2O 50–100 kg of active substance per hectare). Chlorine-containing fertilizers adversely affect cucumber. The fertilizer application rates are adjusted according to the soil nutrient status data.
Cucumber has very high water requirements. During the growing season, 7 to 10 irrigations are given to the crop with the water application rate of 350–400 l per 10 m2 (350–400 m3/ha). Combining drip irrigation with application of water-soluble fertilizers through the drip irrigation system (fertigation) is a highly efficient technique resulting in a more uniform moisture and fertilizer distribution in the root zone, more efficient water use, less soil compaction, and no soil crust formed. Readily soluble mineral fertilizers are given with each water application.
Excellent results are obtained when growing cucumbers on wire trellis. This technique has the following advantages: plants are not injured during cultural operations, harvesting is easier, the efficiency of all the operations is improved and the yield is increased considerably. With the trellis culture, the cucumber plant can be trained in a variety of ways. One possible shaping is to remove all the side-shoots and ovaries from the first 3–5 nodes, pinch side-shoots (suckers) above the first node in subsequent 2–3 nodes and, later on, pinch suckers above nodes 2–4, depending on the plant condition. Once the vine has reached the trellis, it is tossed over the top wire, trained along the plant row and then down the trellis.
Better results are achieved when cucumbers are sown in wind-protected fields or when the field is surrounded by strips (coulisse) of tall-growing crops.
The fruit should be picked every day or every other day and not allowed to overgrow. The overgrown fruit retard the development of young ovaries, causing their wilting. Therefore, regular picking of fruit tends to increase the actual yield.
The most important diseases are Downy mildew, Anthracnose and Bacteriosis. As preventive measures, systematic fungicide sprays with Acrobat MC, Aliette, Curzate, Quadris and Previcur are made every 7–10 days. Using Previcur 607 – a preparation with properties of a growth-promoting substance – has proven to be a very effective control measure, in particular against root rots. Downy mildew can be controlled with Bayleton, Saprol, Topaz and Topsin.
Among the pests attacking cucumbers, the most destructive are the spider mite, aphids and thrips. These can be controlled with Actellic, Talstar and other insecticides. Biologics such as Actofit also provide effective control of spider mites (most effective at temperatures above 18–20˚С)