Garden Fertilizer: Choosing and Using It Wisely

Jun 14, 2021by Juanita Schulze

A productive garden needs suitable soil, water, sunlight and nutrients. Fertilizer can help meet a plant's nutrient needs, but more is not automatically better. The useful question is not which product promises the biggest vegetables. It is what your soil and crops actually need.

Garden fertilizers include liquid products, dry blends and materials derived from plants or animals. Compost and cover crops can also contribute to soil management, although they do not all work like a complete fertilizer. Understanding those differences helps you choose a sensible approach.

David's Garden Seeds® does not sell organic fertilizer. This guide brings together practical advice on choosing fertilizers and using soil-building materials in your own garden.

Start with a Soil Test

A soil test gives you a better starting point than guessing from leaf color or adding a favorite product every season. It can help identify nutrient levels and pH conditions that affect plant growth.

Follow the laboratory's sampling directions and tell it what you plan to grow. Use its recommendations alongside the fertilizer label. If the soil already contains plenty of a nutrient, adding more can waste money or create problems.

Read our soil testing article for related guidance.

Understand the Fertilizer Label

The three prominent numbers on many fertilizer packages describe the guaranteed percentages of nitrogen, phosphate and potash, commonly called N-P-K. They do not describe the entire quality of the product or tell you how much your garden needs.

Compare products using their nutrient analysis, directions, intended use and recommended application rate. A concentrated product and a dilute liquid cannot be compared simply by container size. An all-purpose product is not necessarily the best fit for every bed.

Measure the growing area and the product rather than estimating a handful for each plant. Keep concentrated fertilizer from contacting seeds, stems or roots unless the directions specifically call for that placement.

For label examples and explanations of individual nutrients, read NPK Fertilizer Explained: What the Numbers Mean for Your Garden.

David uses fertilizers from Medina Agriculture Products. Explore Medina Agriculture Products and review each product's label and directions to decide whether it fits your garden's needs.

Organic Fertilizers and Nutrient Release

Many organic fertilizers come from plant or animal materials, including seed meals, fish-based products and processed manures. Their nutrient content and release patterns vary. Natural does not automatically mean suitable for every crop or growing method.

Many organic materials rely on microbial activity to release much of their nutrient content. Temperature, moisture, aeration and the material itself influence that process. Release may slow in cold or dry soil, but there is no single temperature cutoff for every product.

Some liquid or processed products provide nutrients more readily than others. Read the analysis and product information instead of assuming every organic fertilizer acts slowly or behaves like compost.

Fish Emulsion: David's Preference

David has long favored liquid fish emulsion in the garden. That personal preference is part of our growing experience, not proof that one product is best for every soil or crop.

Fish-based fertilizers vary in analysis and concentration. Dilute and apply according to the particular product's directions. If using a hose-end attachment, check that it can deliver the intended rate rather than assuming every setting produces the same mixture.

A strong smell is not a measure of effectiveness. Consider storage, application conditions and access by pets when using animal-derived products.

Seaweed and Plant-Based Products

Seaweed products, alfalfa meal, soybean meal and other plant-derived materials differ in what they supply and how quickly nutrients become available. Some are marketed primarily as supplements rather than complete nutrient programs.

Read the actual analysis instead of treating all natural materials as interchangeable. A material sold for another lawn or landscape purpose is not automatically appropriate for a vegetable seedbed. Check its intended use before applying it around newly sown crops.

Compost Builds Soil, but It Is Not a Universal Fertilizer

Suitable finished compost can help improve soil structure and water management while contributing nutrients. Its composition varies, so adding compost does not guarantee that every crop has a balanced nutrient supply or turn unsuitable material into good growing soil.

Repeated heavy applications can build up nutrients, particularly phosphorus, or salts. Use appropriate amounts and consider the compost's source and testing information where available.

For practical guidance, read How to Make Compost for Your Vegetable Garden.

Bone Meal, Lime and Homemade Blends

Bone meal and other phosphorus sources belong in a feeding plan only where soil and crop needs justify additional phosphorus. More phosphorus does not automatically mean more flowers or fruit.

Lime changes soil pH and is not a routine ingredient for every vegetable garden. Dolomitic lime also supplies magnesium, which may or may not be needed. A blend containing agricultural lime and dolomitic lime can raise pH unnecessarily if the soil is already suitable or alkaline.

Mixing several natural ingredients does not guarantee a balanced fertilizer. Nutrient content varies, and volume measurements alone may not provide the rate your crop needs. Account for nutrients already supplied by compost and other products before adding a homemade blend.

If the calculation is unclear, ask your local Extension office or soil-testing service for help. There is no single recipe that reliably revitalizes every poor soil. Compaction, drainage, pH and nutrient problems need different solutions.

A Family Lesson from Cow Manure

Juanita remembers her grandfather, Floyd Pitcher, using cow manure in his large vegetable garden in Hyde Park, New York. His garden produced food for preserving and plenty to share with family and neighbors.

That memory is a reminder of how rewarding good soil care can be. It is not a reason to assume that any manure, in any condition or quantity, belongs beside a crop you are about to harvest.

Chicken, Cow and Rabbit Manure: Think Beyond Plant Burn

Animal manures can supply nutrients, but they can also contain pathogens, salts, weed seeds or other unwanted materials. Their nutrient concentrations differ, and bedding changes the mixture further.

Fresh poultry manure can injure plants, but plant burn is only one concern. Rabbit manure should not be described as automatically safe to apply around edible crops merely because it may be less likely to burn plants.

For a home food garden, choose properly treated products with clear directions, or obtain reliable guidance for manure handling, composting and application timing. Simply leaving manure in a pile or calling it aged does not establish that a managed composting process has reduced pathogen risks. Finished appearance alone is not proof of treatment.

Do not place untreated manure on edible plant parts or use it as a routine side-dressing near harvest. Do not treat incompletely decomposed material as finished compost. Never use dog or cat manure in vegetable garden soil or a compost pile intended for it.

University of Maryland Extension's organic matter and soil amendment guide explains manure considerations and ways to reduce pathogen risks.

Use Cover Crops with a Plan

Cover crops can protect soil and add organic material. Legumes can contribute nitrogen under suitable conditions, while grasses and other species offer different benefits. Select a crop suited to the season and your intended planting schedule.

Plan how and when you will terminate it before sowing vegetables. Mature, bulky material can take time to break down, and an unmanaged cover crop can become a competitor. Planting every cover crop in fall and turning it under on one fixed schedule is not appropriate everywhere.

Apply Nutrients Where and When They Are Needed

Consider the crop's growth stage and the soil-test recommendation. Some plantings benefit from a measured application before planting and a later feeding; others may need less because the soil already has adequate nutrients.

Keep fertilizer on the intended growing area and away from drains and waterways. Avoid applications likely to wash away in heavy rain, and follow label directions for watering in a product. Do not increase the concentration to make a struggling plant recover faster.

Yellowing, wilting or slow growth can come from waterlogged roots, drought, cold soil, pests, disease or other causes. Diagnose the problem before adding more fertilizer.

Containers and Recordkeeping

Container gardens need their own approach. A potting mix may already contain fertilizer, and a ground-soil recommendation cannot simply be transferred to a pot without adjustment. Match the feeding plan to the crop, growing medium and product.

Record what you apply, how much and when. Combine those notes with soil-test results and plant observations so next season's decisions are based on evidence rather than habit.

Organic Does Not Mean Unlimited or Risk-Free

Organic and manufactured mineral fertilizers can both be misused. The practical choice depends on nutrient needs, product characteristics, availability and your growing approach.

Use protective equipment as directed and store products securely away from children and pets. Avoid collecting unknown animal waste or disturbing guano deposits as a do-it-yourself fertilizer source.

A healthy garden depends on light, water, drainage, root space and suitable nutrition, not simply more products. Choose materials for a clear purpose and resist adding something just because it sounds beneficial.

Frequently Asked Questions

What is the best fertilizer for every vegetable?

There is no single best choice for every soil and crop. Start with soil information and choose a product that supplies what is needed at an appropriate rate.

Can compost replace all fertilizer?

Sometimes soil and compost supply enough for a particular crop, but not always. Compost composition and crop needs vary, so testing and observation matter.

Is rabbit manure safe because it is called a cold manure?

That term does not establish food safety. Consider treatment, handling, application timing and pathogen risks separately from the possibility of plant burn.

Should I fertilize every time I water?

Only if an appropriate product and feeding program specifically call for it. Follow directions suited to the crop, growing medium and product rather than applying one schedule to every garden.