Foliar feeding addresses the immediate needs of a growing crop, as opposed to long-term soil deficiencies, by spraying water-soluble fertilizers onto the leaf surface of the plants. All plants absorb nutrients through their leaves and stems, using stomata—little openings similar to the pores of our skin. Plants absorb foliar sprays 20 times faster than soil-applied nutrients. Foliars help plants compensate for soil deficiencies (low fertility, low soil temperature, etc.) during the growing season.
Foliars fortify plants facing other types of stress as well, such as drought, heat, cold, mechanical or insect damage or the onset of disease-susceptible periods. Foliar feeding can also be timed to encourage and/or enhance critical points in the plant’s growth cycle, such as seedling emergence or rapid growth phases or flowering, fruiting and seed formation. Many crops benefit from 6–8 foliar applications per season. Some growers apply weekly foliars at low concentrations to improve nutrient balance.
Foliar feeding should not be done in the heat of the day. Leaf stomata (pores) close at temperatures above 85°F
Foliar feeding is best done in the early hours of the day, because spraying in the evening may encourage powdery mildew. If evening feeding is necessary, do it a couple of hours before sunset.
If using a micronized substance, be sure that it is fully "in solution" before spraying. Less soluble powders may also need frequent agitation during spraying.
Therm-X70 is the best spreader-sticker on the market. Check the spray mixture pH using a pH meter and make sure it is between 5.5 and 6.5 for maximum effect. Apple cider vinegar is excellent for lowering a high pH. Farmers should measure the oxygen content of their foliar solution with an ORP Meter. If the ORP reading is below 150, add 35% food grade hydrogen peroxide to improve uptake. All of the foliar materials mentioned above can be combined in the sprayer. Add Therm-X70 last, to reduce excess foaming.
Home Gardeners Start with a nitrogen fertilizer like PVFS Liquid Fish. Combine this with a kelp extract (PVFS Kelp or Maxicrop). Then, later in the season, to encourage flowering rather than vegetative growth, hold back the nitrogen and continue with kelp. Commercial Growers use plant tissue testing, as well as sampling with field meters and refractometers see Soil Monitoring Tools section to determine foliar needs and responses. It contains everything necessary for plant health and it can perform marvels for your crop. To address specific needs or deficiencies, consider the following: For calcium, use Calcium 25. To increase potassium, add Soluble Sulfate of Potash. Kelp extracts (Kelp or Maxicrop) are the best general source of trace minerals.
Fertilizing through an irrigation system is referred to as Fertigation. Historically, the products used (known as “injectables”) in this type of application have primarily been conventional (nonorganic), or, if organic, uneconomical. Now that micronized organic fertilizers have been developed, these limitations have been minimized. Irrigation lines should always be cleaned after fertigation by flushing with clean water before and/or after fertilizing. Use Therm-X70 when flushing irrigation lines.