As a crop choice for greenhouse growers, cucumbers remain an excellent option. These long or snack-sized seedless vegetables continue to be popular with consumers because of their consistently high quality, long shelf life and great taste.
The USDA states that U.S. demand for fresh cucumbers has been on an upward trend since the 1970s. In addition, import volume into the U.S. (mostly from Mexico and Canada) has continued a 50-year upward trend, eclipsing domestic field-grown production which started to decline around 2010. “Imports grew from a 35 percent share of availability in 1990 to 1994 to 80 percent in 2015 to 2020,” states the USDA. “By 2020, imports accounted for almost 90 percent of the domestic market.”
It’s no surprise, therefore, that in 2022, the De Ruiter Experience Center in The Netherlands will be testing hundreds of new greenhouse cucumber varieties in a new dedicated facility after previously conducting trials only on tomatoes. This will help growers address challenges with pathogens and achieve higher yields than ever before.
Due to the popularity of greenhouse food production in general (due to the consistently high-quality products), more growers are now investing in large-scale cucumber greenhouse farming, which usually includes year-round production.
Because of its scale and the risk of disease and other factors that may reduce yield, controlled environment food production must employ the latest greenhouse innovation technology and best practices to ensure high yields and high-quality harvests. Disease control through adequate treatment of growing medium and irrigation water treatment system is critical.
Greenhouse cucumber plants grow at a rapid pace, with fruit production starting 60 to 70 days after seeding. The temperature should range between 75° and 80° F (24° and 26° C), and while higher brief daytime temperatures can be tolerated, prolonged heat is a quality risk. Greenhouse cucumbers can be grown at much lower temperatures to save on heating costs, but because it slows the growth rate and lengthens the production cycle, it may not be a viable option for some growers.
This crop is grown both in soil (well-drained and low in soluble salts) or in a soilless growing medium such as peat-lite (a mixture of sphagnum peat and vermiculite or perlite) or sawmill by-products (mixtures of bark, wood chips and sawdust). Greenhouse cucumbers can also be grown hydroponically.
For soil cultivation, growers add potassium, phosphorus and nitrogen before planting, and the soil should also be tested ahead of planting for pH and micro-mineral levels. If a deficiency of a minor mineral becomes apparent during crop growth, plants can be treated with foliar applications.
The use of manure is feasible but must be managed closely in terms of soil salinity.
In soilless cultivation, a nutrient solution is applied in every irrigation cycle using different irrigation systems, for example through drip irrigation tubes.
There are two viral pathogens, cucumber mosaic and watermelon mosaic, that are serious threats. Aphids can transmit mosaic viruses from other susceptible crops and weeds from outside the greenhouse. Powdery mildews (Sphaerotheca fuligenea) are also a problem, but resistant varieties are available. Gray mold (Botrytis cinerea) infections can appear when humidity is not properly controlled. Infections of Pythium sp. can occur in cucumber plantings, known as ‘post-emergence damp-off.’
Crooking (excessive curving of the vegetable) can arise due to a variety of factors but humidity, temperature extremes and lack of proper fertilization are believed to be contributors. Insects that can jeopardize greenhouse cucumbers include white flies (Trialeurodes vaporarium), two-spotted mites (Tetranychus urticae), vegetable leaf miners (Liriomyza sativae), cabbage loopers (Tricoplusia ni), and greenhouse thrips (Heliothrips haemorrhoidalis).
Pythium, commonly referred to as water molds, can cause serious infections for many greenhouse vegetable crops, including cucumbers. An infection of Pythium can result in significant crop losses if not treated and several species of Pythium can lead to “damping-off in seedlings and crown and root rot in greenhouse cucumber, pepper and tomato crops,” according to the British Columbia Ministry of Agriculture, Food and Fisheries.
Growers are looking for ways to reduce their inputs, especially with the rise of sustainable agriculture practices which focus on reducing water, chemical pesticide, and fertilizer use. Sustainable, chemical-free methods of controlling disease, increasing fertilizer uptake efficiency, and improving irrigation water efficiency are now available with AgTech.
Besides new innovative technologies that are automating harvesting and packing processes and AI systems that better control the growing environment, there are also AgTech solutions that enhance irrigation water. The injection of nanobubbles into irrigation water is emerging as a superior water treatment method that prevents and reduces pathogens such as Phytophthora and Pythium through the unique chemical and physical properties of nanobubbles.
Quality irrigation water is imperative for large-scale cucumber plant and root health as well as crop production. Greenhouse growers often reuse irrigation water from source water basins, resulting in decreased irrigation water quality over time, including decreased dissolved oxygen and increased bacteria and algae growth. Without oxygen present in the root zone, plants cannot take up nutrients and water from their roots leading to poor plant and root health and low cucumber crop production.
When nanobubbles are created using oxygen, they supersaturate the water with dissolved oxygen at a sustained high level. Supersaturated levels of dissolved oxygen (DO) in the water will improve the availability of oxygen which consequently reduces root pathogens, improves root growth and health leading to enhanced nutrient absorption. All this can be achieved relatively quickly and cost-efficient when using an oxygen generator that produces oxygen with 93% purity and a technology that transfers gas into water with an extremely high 85% efficiency.
Green Circle Farms in Leamington, Canada, reported high levels of Pythium in their seven-acre cucumber and pepper greenhouse. After implementing Moleaer’s nanobubble technology, they noticed suppressed disease resulting in reduced chemical treatment costs. Green Circle Farms also noted nanobubble enriched irrigation water led to better root health, improved plant vigor and increased crop yield.
In addition to increased dissolved oxygen levels, nanobubble’s unique properties have added benefits to enhance irrigation water for cucumber growers. When nanobubbles come in contact with contaminants, they collapse producing hydroxyl radicals, a highly effective oxidant, that lyses bacteria cells, breaks up biofilm and algae, and reduces pathogens. Nanobubbles also improve irrigation water quality by reducing its surface tension which increases soil moisture and nutrient uptake as the water is held near the root zone longer. This has helped cucumber growers improve fertilizer efficiency by improving mixing in fertigation tanks to reduce fertilizer runoff and loss from leaching as well as creating improved conditions at the root zone to increase plant nutrient uptake efficiency.
Demand for fresh indoor-grown greenhouse cucumbers, and greenhouse food production in general, will continue to increase. Greenhouse growers must use every tool at their disposal, including innovative technologies, to prevent disease and ensure high-quality yield through super-high root oxygenation and the unique properties of nanobubbles and other aspects of production that support plant health and vigorous growth.