Organic liquids often give plants the quick boost they need to grow strong and resist diseases and pests. Countless traditional recipes for homemade liquid "teas" exist, using everything from manure to stinging nettle. Gardeners can also readily find organic liquids from sea-based products, both fish and plant, at nurseries. Finally, some intrepid farmers and home gardeners are even experimenting with milk and urine.
Liquid fertilizers work especially well as foliar or root feeders. In foliar feeding, the gardener applies the liquid plant food directly onto the leaves of the growing plant, allowing for a quick boost of nutrients. Watering around the base of the plant with liquid fertilizer helps get the nutrients straight to the roots. Vegetables respond extremely well to this treatment, especially ones that set fruit like tomatoes, pepper and eggplants. Apply at transplant and at fruiting time, at least once a week.
Manure and Compost Teas
Thrifty gardeners usually make aged manure or compost fertilizer teas by placing the material in a burlap bag, soaking it in a large container of water for a number of days or weeks, and then using the infused water via watering can or bucket. Fancier contraption exist that feature a spigot and hose attachment. After several weeks, the brew is ready to use. Put 10 to 16 parts water to 1 part fertilizer tea in your sprayer or watering can, and apply liberally to plants.
A common European recipe for herbal fertilizer tea contains stinging nettles, while American organic farmers seem to prefer comfrey. Obviously the two plants can be combined for a double-benefit fertilizer. To make the nettle plant food, use gloves through most of the process. The process follows that of manure tea, although the material needn't be confined to a burlap bag.
Brews for Disease and Pest Control
Many of the liquids listed here as fertilizers also work well for combating disease and plants, simply because strong plants are resistant to these ills. But it's worth trying some of the hundreds of folk remedies of botanical teas, including horsetail tea to fight rust, crushed, garlic or peppers for aphids and wormwood for moths and caterpillars.
From the Dairy Aisle
Some gardeners swear by powdered or liquefied eggshells to add calcium and phosphorous to their soils and directly onto plants. To use eggshells in liquid form, simply steep about two dozen eggshells in a gallon of water overnight and strain. Milk provides nitrogen, and can be applied at a strength of about four parts water to one part milk.
Nitrogen from the Sea
Most garden centers stock organic liquid fish emulsion or kelp extraction, or sometimes a mixture of both. The mixtures are especially high in nitrogen, but also contain other nutrients, depending on the formula. The preparations either come in concentrated form, which should be diluted with water, or the more expensive pre-mixed varieties. Follow the directions on the label.
Believe it or not, human urine makes an ideal plant food. If used fresh, and well-diluted with water, urine provides plenty of nitrogen to plants. Interested gardeners should use clean jars to collect the urine, and dilute it in water by a ratio of about 10 parts water to 1 part urine. When applying, avoid getting the mixture on the foliage. The American Cancer Society's Journal of Agricultural and Food Chemistry deems human urine a cheap, pathogen-free alternative to commercial liquid fertilizer.