This article on feeding cucumbers explains the best fertiliser mixes to use for growing cucumbers for the home gardener.
Use the Right Feed Mix for Better Cucumbers & More of Them!
Greenhouse cucumbers are generally grown in the same house as tomatoes, peppers and aubergines by home gardeners and naturally enough the gardeners tend to just feed the cucumbers with the same feed they are using for the tomatoes.
A tomato feed will be near ideal for peppers and aubergines, all three belong to same family, solanaceae, as potatoes but cucumbers are cucurbits – members of the Cucurbitaceae family – like courgettes, marrows, pumpkins and squashes. A tomato feed is not ideal for this family and especially not the cucumber.
Generally the result of feeding cucumbers with a tomato feed are acceptable but much better results can result if you feed cucumbers with a more appropriately balanced fertiliser.
High Nitrogen Requirement in Cucumber Feed
By looking at a mature cucumber plant it’s apparent the leaf area is much greater than a mature tomato plant. Since the fuel of leaf growth is nitrogen, it’s obvious that cucumbers require more nitrogen than the other major nutrients, unlike tomatoes whose prime need is for potash. A good quality tomato feed will supply the major nutrients (NPK) in a ratio around 10:10:30 usually with added nutrients such as magnesium and other trace elements.
Looking at the recommendations for commercial cucumber growers, they agree that a much higher nitrogen level is required along with magnesium, calcium and other trace elements like boron, iron and manganese.
Easily Available Fertilisers to Feed Cucumbers
Another option is to use S-Chelate 12-Star which provides calcium in a chelated form so remaining bio-available along with NPK and other micro-nutrients.
Many organic growers will use comfrey liquid as a greenhouse tomato feed. It’s well suited to this as the NPK ratio is very similar to commercial tomato feeds but, once again, it’s not ideal to feed cucumbers.
A better organic feed for cucumbers would be a nettle tea, made by steeping nettles for 3 to 6 weeks in water. Another organic liquid high nitrogen feed that would benefit cucumbers can be made by steeping a hessian sack full of fairly fresh horse droppings in a barrel of water until the water turns dark brown. This is called a muck tea.
A good level of home-made compost in the border should provide the trace element requirements to feed cucumbers.