Maximum Yield USA December 2016 | Page 137

CHLORIDE LEVELS A similar, yet often misdiagnosed, issue stems from the cucumber plant’s sensitivity to chloride. Chloride uptake by cucumber plants accumulates in the foliage, producing a band of pale green tissue around the leaf margin, followed by scorching and browning of the edges. Cucumbers need a good-quality water supply that doesn’t contain high sodium chloride (common salt) levels. Sodium chloride can be a common problem in many water supplies and where domestic water softener units are being used, and recirculating systems are particularly more prone to chloride buildup when sodium chloride is present in the water supply. The use of an alternative water source or reverse osmosis is a good option to clear things up. In addition, avoid using fertilizers and nutrient products that contain potassium chloride and calcium chloride. “ DUE TO THE rapid and prolific nature of fruit production, cucumbers have a particularly high requirement for potassium, much of which ends up in the fruit tissue and plays a role in flavor, firmness, shelf life, and overall compositional quality.” CUCUMBER NUTRITION Cucumber nutrition is like that of other heavily fruiting crops, with an emphasis on the use of vegetative and fruiting formulations as the plant moves through the different growth stages. Due to the rapid and prolific nature of fruit production, cucumbers have a particularly high requirement for potassium, much of which ends up in the fruit tissue and plays a role in flavor, firmness, shelf life, and overall compositional quality. Potassium also affects stress resistance, plant turgor, and osmotic control. However, deficiencies can be common in recirculating systems with heavily fruiting cucumber crops. The recommended potassium levels during fruiting are 200-350 ppm. Using a potassium booster or aggressive bloom nutrient products usually provides these levels. Calcium levels are also essential during this phase and should be boosted as the first fruit are set. Boron is another common nutritional problem with cucumbers. Plants deficient in this nutrient develop fruit that has cavities or is hollow in the center. Young fruit may also drop from the plant, have corky markings or yellow streaks on the skin, or develop a curved shape, while newer leaves may become distorted. Recommended levels of boron in the nutrient solution are 0.5-0.8 ppm. SYSTEM SHARING While it’s common for an indoor garden to have a number of different plant species sharing the same recirculating nutrient solution and system, cucumbers can place a particularly high demand on oxygen and certain nutrients. They also produce large amounts of organic root exudates. This may require a higher frequency of solution replacement, additional methods of oxygenation, and regular monitoring, as well as keeping a check on potassium levels during the fruit phase. Maximum Yield USA  |  December 2016 135