Plants and animals have some of the same nutritional needs. Tomato plants can suffer from calcium, magnesium, potassium, iron and manganese deficiencies just like humans can. Many of these minerals are found in multivitamins manufactured for human use. In fact, many organic vitamins pull these minerals straight from tomato and other vegetable plants. You can resolve some vitamin and mineral deficiencies in plants, such as tomato plants, by giving them a multivitamin.
Send a sample of the soil that your tomato plants are growing in into your local county extension office to be tested. The report will reveal the mineral content of your soil. While not harmful, a multivitamin supplement will be unnecessary if your soil is quite fertile. However, if you find that there is a dearth of a certain necessary mineral in your soil, look for a multivitamin with high amounts of that mineral.
Find an appropriate multivitamin. The best multivitamins for plant use are organic and contain minerals derived from plant sources.
Crush the multivitamins into a fine powder using your mortar and pestle.
Mix the water, sparkling water and crushed multivitamin in the large container.
Transfer the solution into your watering can. Water your tomato plants deeply at their base until the soil is saturated but not soaking.
Water your tomato plants with the multivitamin 3 to 4 times per growing season. The vitamin C found in most multivitamins can help your tomato plants with weather changes. If possible, water them with multivitamins a week or so before the seasons change.