The effect of different fertilizers on tomato plants

Tomato plants are highly adaptable, low-maintenance plants that yield a desirable fruit for a multitude of culinary uses. However, fruit production is influenced greatly by the care practices employed. Even the fertilizer can affect plants in different ways. If your plants aren't achieving the growth and development you hoped for, chances are the problem has to do with the fertilizer.

Planting Preparation
Although tomato plants grow well in just about any soil, you can enhance their growth and development by preparing the soil before planting. Fortify the soil by adding a layer of organic fertilizer such as compost, manure or peat moss. These fertilizers increase the soil's nutrient content and aid in plant growth, as they help roots absorb moisture and nutrients.

Nitrogen
When your tomato plants look lush, green and healthy but fail to form fruit, the fertilizer might be to blame. A fertilizer with too much nitrogen (N) can make plants grow quickly, but can also impede fruit development. In particular, plants that receive too much nitrogen develop many leaves but few or no blossoms, which are required for fruit to set. Change to a more balanced fertilizer formula of equal or nearly equal amounts of nitrogen, phosphorous and potassium (NPK).

Phosphorous
Tomato plants probably aren't getting enough phosphorous if they appear healthy but have fruit that never ripens or fruit of irregular size. Phosphorous (P) encourages fruit development. Switch to a fertilizer with higher amounts of phosphorous if your tomato plants have a fruiting problem.

Potassium
Fertilizers with concentrations potassium (K) of 50 percent or more can cause a tomato plant to suffer from calcium deficiency. A calcium-deficient plant growing in less-than-optimal environmental conditions is prone to blossom rot, which causes blossoms to drop prematurely. Blossom rot severely reduces crop production because the fruit isn't able to form. Apply 3/4 cup of lime to the soil around each plant to counteract the fertilizer's effects and replace the fertilizer formula with one that contains less potassium. Lime helps reverse the damage done to the plant before the nutrient imbalance is corrected.

Considerations
A fertilizer low in nitrogen, high in phosphorus and medium to high in potassium is often ideal for initial soil preparation, according to horticulturist David Trinklein of the University of Missouri Extension. He suggests an initial application of a fertilizer with an NPK ratio of 8-32-16 or 6-24-24. Do not use a fertilizer containing urea or ammonium nitrate because those chemicals can interfere with plant development. Once plants begin to develop, apply a balanced fertilizer with NPK ratios of 5-10-5 or 5-10-10 to enhance normal plant maintenance. Apply it at a rate of 1 lb. per 100 square feet.

Tomato fertilizer ingredients

Using a fertilizer designed for the needs of tomato plants will help you grow stronger, healthier plants that, in turn, will produce more tomatoes. Tomato-plant fertilizers consist of three main components: nitrogen, phosphorous and potassium. Before planting your tomato plants, apply a tomato fertilizer to the garden's soil at a rate of 1 pound per 100 square feet. Work the fertilizer into the soil, to a depth of 6 inches, with a rototiller.

Nitrogen
Nitrogen, also referred to as N, is the fertilizer component that contributes to the tomato plant's growth. While it's a good idea to use a fertilizer that contains nitrogen for your tomatoes, the fertilizer should not be high in nitrogen. Excessive nitrogen applied to tomato plants results in accelerated leaf and stem growth, but reduced fruit production. A garden fertilizer such as 8-32-16 or 6-24-24 is recommended. The first number represents the percentage of nitrogen in the fertilizer and, as you can see, the nitrogen level is much less than the phosphorus and potassium. Once the tomatoes reach the size of golf balls, add 1 tablespoon of ammonium nitrate around the base of the plant, and again three to six weeks after, to boost tomato size.

Phosphorus
Phosphorous, often referred to as P, is the fertilizer component responsible for growth of the roots and maturation of the plant. When looking for a tomato fertilizer, choose one in which the phosphorous, always represented by the second of the three numbers, is either the highest number or equal to the last number, which represents potassium. To produce the phosphorous for fertilizer, rock phosphate is treated with acid to make it soluble. Just how much of this soluble phosphorous actually gets to the tomato plant depends on factors such as the soil's moisture content, pH level, minerals and temperature. Soils with a fine texture, such as clay soils, will hold more of the soluble phosphorous than rough, sandy soils. High pH levels and excessive moisture due to high rainfall also lower the level of phosphorous that is absorbed by the tomato plants.

Potassium
The role of potassium, also referred to as K, is not as well known as that of the other two elements. What is known is that potassium is believed to be responsible for the movement of nutrients, carbohydrates and water within the tomato plants, as well as increasing the plant's resistance against disease and insects. This makes it just as essential as nitrogen and phosphorous, because without potassium, tomato plants become stunted and produce fewer tomatoes.

How to use seaweed to fertilize tomato plants?

Seaweed is among the best gifts nature makes available for the gardener. Seaweed will benefit your garden any time of year, but it is especially useful as a mulch to protect plants during hot, dry weather. In our garden, we’ve come to rely on seaweed as a valuable, yet free, source of fertilizer, mulch and organic pest control all in one natural material.

Benefits of seaweed for gardening

Gathering seaweed for the garden has always been a favorite outing for our family. We usually take a small skiff to a nearby beach and load up with as many sacks as we can safely transport home. It’s fun for children, as they can participate as well as an adult, or they can simply enjoy the beach while we gather the seaweed. As we fill up our sacks, our thoughts drift to the many benefits this will bring our garden.

• Saves water, keeps soil moist at ground level

The purpose of any mulch is to keep garden soil from drying out at the surface. And by preventing moisture from evaporating, mulch reduces the need for watering. The practice of mulching is essential in areas where conditions are hot and dry.

• Eliminates the need to weed

Mulch covers the soil and blocks new weeds from sprouting. Because the soil beneath the mulch remains moist, any weeds which do manage to sprout through the mulch are easy to pick.

• Repels slugs and other pests

Slugs are immediately repelled by two things – salt and sharp-edged materials. Seaweed has a natural salt content which repels slugs, and within a few days of application it dries and becomes quite crispy. Slugs do not like “crispy” surfaces, as the sharp salty edges cut into the soft body tissue. While some mulches may provide hiding spots for slugs, earwigs and other pests, seaweed mulch does not have this disadvantage.

• Enriches the soil

Seaweed is a broad spectrum fertilizer that is rich in beneficial trace minerals and hormones that stimulate plant growth. Seaweed is high in carbohydrates which are essential building blocks in growing plants, and low in cellulose so it breaks down readily. Seaweed shares no diseases with land plants.

• Boosts lethargic plants

Seaweed fertilizer contains an abundance of fully chelated (ready to use) micro-nutrients which can be readily absorbed by plants without any further chemical decomposition needed.

• Helps lighten the soil

Compacted soil can benefit as seaweed mulch breaks down. As the material becomes incorporated into the soil, aeration is improved and the soil becomes more crumbly and moist.

• Does not contain weed seeds, unlike bark mulch

Two years ago we used commercial bark mulch to cover our garden pathways for the purpose of blocking weeds. Today, these pathways are sprouting horsetail, an invasive weed which can be difficult to eradicate. Seaweed does not bring any foreign weed seeds into your garden.

• It’s free!

But what about salt? Is this a problem?
We have been using seaweed as mulch for many years and have not seen any adverse effect, such as a salt overload in the soil. In our region we have plentiful rain. If you are concerned about salt, seaweed can be spread out over the driveway and rinsed with a hose. Of course this is not an issue if you are using freshwater lake weed.

Gathering seaweed for use in the garden

• Gather ‘mid-beach’

Seaweed is often found scattered on the beach from the water’s edge to the highest point of recent high tides. The seaweed ‘mid-beach’ is drier than seaweed at the tide line and therefore lighter to carry. It also has fewer bugs than the seaweed high up on the beach, and is a little more pleasant to gather.

• Use fine, broken up seaweed

Look for patches of seaweed that are smaller in leaf size as this will be easier to apply as mulch. Set large kelp fronds aside – the wide pieces are difficult to form around plants in the garden beds. The kelp can be used to make ‘kelp tea’ and used as a foliar spray to deter insect pests.

• Use onion sacks or woven poly bags or buckets

We like onion sacks for gathering seaweed because they are lightweight, the water drains out easily, and they are easy to grip. They are also small enough that we don’t overload ourselves with heavy sacks. Woven poly bags are great if you can find them – ask at your whole foods store because these bags are used to ship whole grains. Don’t use plastic garbage bags as they are too difficult to handle. Your hands get slimy when picking seaweed and this transfers to the bag making it slippery.

• Limit your impact by picking lightly from several areas

Each patch of seaweed provides food and shelter for many small marine species. Pick no more than a third of the seaweed from any patch, and move on to another spot.

Applying seaweed to your garden beds

• Apply seaweed within 36 hours of gathering

Seaweed breaks down quickly, especially when in an enclosed sack. If you leave the seaweed in the sacks too long, it gets sludgy and slimy, and is more difficult to spread evenly over the soil.

• Apply thickly, at least 4 – 6” deep

Spread the seaweed thickly and evenly around the garden beds to cover any exposed soil. You may think you’re adding too much, but in a few days you will think otherwise.

• Reapply in one week, another 4 – 6” deep

Seaweed shrinks when it dries. Even a generous layer of seaweed will dry in a few hot days to expose much of the soil. The seaweed will become very stiff and crispy. Ideally, you should reapply in a week or so, and this second application will dry out but still provide good coverage for your soil. Once we make the second application, our beds are usually well-mulched for at least 4 – 6 weeks even in hot, dry weather.

• Leave a clear space around plant stems

Once you have spread the seaweed around the plants, push it back just a little from the plant stems so they are not in direct contact with the wet seaweed. Once it dries, the seaweed will naturally ‘shrink’ away from the stems, but it’s a good habit with any mulch to keep plant stems clear.

• It’s OK to mix seaweed with other mulch

We use whatever mulch we can get, and it doesn’t matter if you mix several varieties of mulch on a garden bed. For example, our tomatoes are mulched with dried grass clippings (straw) and topped with seaweed. In the fall we’ll add maple leaves. Mix and match, it matters not.

• Don’t use seaweed to cover garden pathways

Some people use seaweed as a pathway mulch but this is a waste of good seaweed, which is better used on the garden soil for the reasons listed above. If seaweed is used on pathways, it quickly thins out to allow weeds to get through. And the seaweed will become very slippery underfoot after a rain.

Is sugar a good fertilizer for tomato plants?

The Facts
Sugar acts as a counter-balance to excess nitrogen in the soil. These types of soils, known as "rich" soils, promote foliage at the expense of flowers.

Function
Carbons require nitrogen to decompose, so adding carbon-rich additives to the soil help deplete it of excess nitrogen. Wood chips are an excellent form of carbon for large areas but sugar works equally as well for small gardens.

Considerations
While sugar is not really considered a fertilizer, in that it adds no nutrients to the soil, it is a carbon that will use up excess nitrogen. Use 4.5 lbs. of sugar for each 10 square feet of soil.

Fish emulsion & tomatoes

It's nearly impossible to grow tomatoes without giving them regular fertilizer. Many gardeners prefer using organic fertilizer on their homegrown fruit, but ordinary compost and manure--while useful when growing tomatoes--doesn't adequately feed tomato plants. Many other types of organic fertilizer aren't adequate for tomatoes, either, producing spindly, sickly plants. That's why fish emulsion is so popular among tomato gardeners.

What Is It?
Fish emulsion (sometimes called fish fertilizer or liquid fish emulsion) is an organic, liquid fertilizer made from byproducts of the fish industry. It's particularly useful for lawns and leafy green vegetables, having a high level of nitrogen. It's typically sold as a concentrate that gardeners dilute with water. Although it often has a fishy smell, deodorized versions are available at gardening centers.

Nutrients
Commercial fertilizers are labeled with three numbers separated by dashes. These numbers tell gardeners the percentage by weight of three nutrients every plant needs: nitrogen, phosphorus and potassium (N-P-K). Most fish emulsion is rated 5-1-1 or 5-2-2.

Fish emulsion, applied twice weekly, helps tomato plants grow larger and faster than plants that are not fertilized. Specifically, the nitrogen in the fish fertilizer encourages lots of leaves and branches, which help support the tomato plant's large root system and bountiful crop.

Why use it?
Tomatoes require plenty of water. However, watering depletes soil of nutrients tomatoes need to thrive. Therefore, frequent fertilizing of tomatoes is necessary. Although non-organic fertilizers may be used on tomatoes, they may add too much salt to the soil, thereby stunting the plant. Fish emulsion is a better choice because there is no danger of over-salting--yet the emulsion releases nutrients quickly to the tomato plant.

How to Use It?
Dilute the fish emulsion according to the manufacturer's directions, then put it in a garden sprayer and apply it to the tomato plant's leaves. Do not apply during the hottest part of the day, since this could potentially burn the plant's leaves--and will certainly make the fertilizer scent stronger.

How to Make Your Own?
It's possible to make your own fish emulsion, but fishing for the purpose of using the catch for fertilizer is discouraged. Home-made versions of fish emulsion can contain higher levels of nutrients, since already processed, commercial fish have less oil and bones, and therefore less proteins and other nutrients. In addition, home-made versions can have higher levels of fungi and bacteria--both essential to a healthy garden.

To make your own emulsion, take a five-gallon bucket (placed in a sunny location) and fill it halfway with leaves or sawdust. Add fish and fill with water. A couple of tablespoons of molasses added to the mixture will help it decompose faster and can reduce the smell.

Allow the mixture to ferment for three months. A layer of oil will form on the top of the water; skim it off with a large spoon and place in a separate container. Dilute with water (about 1-to-1) before spraying plants.

The best fertilizer combination for tomatoes

Many gardeners have secret fertilizer recipes for growing the biggest and tastiest tomatoes. Even agriculture experts offer competing nutritional theories. Most everyone agrees on several details. First, use minimal nitrogen on tomatoes---nitrogen supports vine growth, not flowers and fruit. Second, make sure your soil pH is nearly neutral, between 6.5 and 7.0. Third, start your fertilization program with a comprehensive soil test. Don't apply phosphate or potassium, for example, if your soil has plenty already.

Best Combinations

According to University of Missouri Extension, a standard tomato fertilization program starts with adding fertilizer to the soil before planting. Because tomatoes are heavy feeders, supplement with regular side applications of fast-release fertilizer during the growing season. A fertilizer low in nitrogen (N), high in phosphorous (P) and medium or high in potassium (K)---the three numbers in fertilizer nutrient analysis, always in that order---is ideal for tomatoes. The best analyses for tomato fertilizers are 8-32-16 and 6-24-24, according to the University of Missour. These are high in phosphorous in order to support flower and fruit development. But Cornell University's College of Agriculture prefers a balanced fertilizer, with similar amounts of N, P and K, and just about any balanced fertilizer will do, such as 10-10-10.

Inorganic Combinations

Sometimes called synthetic or chemical fertilizer, inorganic fertilizer types are those with N, P and K immediately available for plant use. Inorganic fertilizers also come in slow-release forms, which are typically more expensive. Cornell's suggested 10-10-10 all-purpose fertilizer is easier to find than the University of Missouri's 8-32-16 and 6-24-24 recommended formulations, but both should be available in slow- and fast-release forms. Very easy to use as 60-day slow-release fertilizer "spikes" you stick in the ground near each tomato plant, Jobe's Fertilizer Spikes for Tomatoes have a nutrient analysis of 8-24-8. Other good tomato fertilizers---though they may be labeled as flower or "bloom" fertilizers---will be high in phosphorous, with nutrient ratios such as 10-20-10, 15-30-15, 12-24-12 or 8-16-8. Miracle-Gro Tomato Plant Food, by contrast, is 18-18-21--very similar, proportionately, to all-purpose 10-10-10 fertilizer, just more concentrated.

Organic Combinations

The same general trends in plant nutrient needs and proportions hold up with commercial organic fertilizers, but the process is much more complex. This is because plant nutrients in organic fertilizers are bound up in organic compounds, which are not available to plants for use until these compounds are broken down in the soil by microbes. This makes it harder for gardeners or growers to know exactly how much of any given nutrient is immediately available, although building living, dynamic soil eventually delivers high levels of all nutrients. Commercial organic products feasible for tomatoes include Dr. Earth Organic 5 Tomato, Vegetable & Herb Fertilizer, with a nutrient analysis of 5-7-3, and Fox Farms' Happy Frog Fruit & Flower Organic Fertilizer, with a nutrient analysis of 5-8-4. But organic growers experiment with many approaches, including devising their own fertilizer combinations and blends. To meet the relatively low nitrogen levels needed by tomatoes, for example, some very successful tomato farmers grow legumes or "green manure" crops during the previous season, because legumes "fix" atmospheric nitrogen and make it available in the soil. Composted chicken manure is a good source of both nitrogen and phosphorous. Bone meal is an excellent phosphorous source, and wood ashes provide quick phosphate and potash. Organic fertilizers such as liquid fish emulsion can be used in the garden and also on container-grown tomatoes.

How to feed tomato plants in containers?

Tomato plants grow well in containers, provided the pots are large enough and the plants are kept well-watered and fed. Tomato plants grown in an open garden pull nutrients as needed from the soil. In containers, tomato plants often need more frequent feeding, as the nutrients in smaller quantities of soil deplete quickly. Feed these tomato plants at least once every 10 to 14 days. This is assuming you are using liquid or granules, rather than fertiliser spikes (these are left in the soil).

1. Use a good starter fertiliser, mixed in with the potting soil, when you first plant tomatoes. If you've already planted them in containers, add a water-soluble starter fertiliser to the top 2.5 cm (1 inch) of soil and water it in well. When water starts seeping out of the container base, you've watered deeply enough. If you are using a liquid fertiliser, apply it carefully to avoid splashes and follow mixing directions and application directions fully.
2. Fertilize the plant again in two weeks. This time, use either another water-soluble liquid or granule fertiliser (for tomatoes) or add a tomato fertiliser spike to the pot. Fertiliser spikes release fertiliser gradually over time (up to two months) -- these may be more convenient if you have a very busy schedule. No matter which kind of fertiliser you use, water the soil well so the fertiliser travels down towards the plant roots where the plant can use it.
3. Continue fertilising the plant every two weeks (unless you use spikes), until the first fruit blossoms appear. When this occurs, start fertilising every week throughout the rest of the growing season.

Tomatoes are heavy feeders. They are greedy and like lots of food. Use tomato fertilizer wisely and your plants will reward you.

Why container watering impacts feeding

Tomatoes in pots and containers require frequent watering or they will dry out. But watering leaches nutrients out of container plants. So you need to be especially vigilant to include tomato fertilizer in your container gardening plan to get best results.

Try these top tips for fertilizing tomatoes in pots

• Add a slow-release fertilizer (like Osmocote) to your containers when planting. Nutrients will disperse over time.
• Try grass clippings. They do double duty as mulch. Apply a couple of inches to the soil surface of your containers.
• One easy way to fertilize tomatoes is to mix a small amount of soluble, balanced tomato fertilizer (like Miracle Grow for Tomatoes) into water. Fertilize and water at the same time.
• When it comes to fertilizing tomatoes in pots, little and often is better than a lot, less often. Tomatoes like regular feedings of small amounts of fertilizer rather than infrequent, large doses. Some gardeners swear by weekly feedings or even more often. Others say every two weeks is enough. Take time to find out the best schedule that works for your plants. There are plenty of variables including tomato variety, container size, plant size, your weather, and potting mix type.
• You’ll know you’re feeding plants too much when they produce more leaves than fruit. If production is low or foliage starts to yellow, you’re probably not feeding enough.
• A good fertilizer to use on container tomatoes should have more phosphorus (the middle number in a fertilizer’s 3-number series) than nitrogen (the first number in a fertilizer’s 3-number series). Too much nitrogen can mean lots of leaves and few fruit.
• Avoid feeding tomatoes at the peak of the day or when weather is really hot – say, when temperatures are over 90-95 degrees. Extra nutrients are hard for plants to digest in the heat.