One Fertilizer Habit Most Gardeners Overlook

Growing plants involves a lot more than supplying the right amount of water and sunlight. There are 17 micro- and macronutrients that plants need to thrive. These include carbon and oxygen that are naturally obtained from the air, but primary macronutrients such as nitrogen and potassium typically need to come from the soil. Plants might start to grow slower or produce less healthy harvests if these soil-based nutrients aren't replaced after being absorbed, and this is where fertilizers come in handy. Whether you use organic fertilizers like manure and compost, or synthetic, manufactured fertilizers such as ammonium sulfate, the goal is to reincorporate nutrients or amend other aspects of the soil such as pH level. A mistake that gardeners often make is simply top-dressing their fertilizers to try and achieve a healthy lawn landscape instead of mixing them into the soil.

Nitrogen is one of the more common soil additives, often applied by top-dressing or side-dressing fertilizer in places where natural decomposition isn't supplying enough. Top-dressing means you lay a nutrient fertilizer around the entire plant while it's growing, whereas side-dressing involves just a line of fertilizer often along the edge of a row of crops that require lots of nitrogen such as sweet corn. Tissue testing the soil tells you how much nitrogen you need at a given time. However, the nutrient is easily leached from the soil, so most of the excess you apply could be caught in runoff that contaminates the local water supply. Applying too much in concentrated areas could also lead to fertilizer burn, damaging your plants. Those are a couple reasons why incorporating fertilizer deeper into the soil is easier — and safer — for home gardeners.

Uniformly applying fertilizer across your garden soil and incorporating it into at least the top 4 to 6 inches is known as the broadcast application method. Fertilizers such as bone meal will have a more granular texture, whereas making your own DIY compost may result in more of a moist, soil-like additive you'll have to incorporate. Broadcast application works best with granular fertilizers, both slow-release compounds and water-soluble materials. It should be easy to lay out nutrient particulates by hand, but if you have something larger than a garden bed for your tomatoes, consider investing in a fertilizer spreader to get an even coating across the area.

Avoid applying too much fertilizer early on, especially with the broadcast method. You don't want to find yourself in a situation where your entire garden is inhospitable because a thick layer of nitrogen is damaging your plants before they have the chance to grow. Start with a small amount at the time of planting if you know your soil needs the additive, and see how demand shifts throughout the growing season. 

Tillage is the best way to incorporate fertilizer or manure. This involves turning the soil over with a fork, shovel, or rake. If you have more land to till, you might need heavier machinery. This process should be done during autumn so you can break up plant debris and prevent pests from nesting in it over the winter. Never till wet soil, and keep in mind that tilling could increase erosion. Regardless, tilling increases the likelihood that soil-based nutrients will reach your plants.

Using and tilling fertilizers is an especially important step for container-based plants in potting soil, as this limited growing space will more easily lose its nutrient content. With that in mind, you should avoid applying fertilizers and watering your plants at the same time. Doing both at once increases the odds that you'll be leaching nutrients such as nitrogen out of the soil before it gets incorporated. But there are even more problems to consider with over application of fertilizers than the environmental impact of nitrogen runoff, or potential fertilizer burn. If you're growing vegetables in particular, having too much nitrogen in the soil might result in an abundance of leafy growths with fewer edible crop production.

Shifting to entirely water-based fertilizer methods could be a solution to your woes. For example, a foliar application method involves mixing fertilizer and water before spraying that solution directly on your plants. Trickle irrigation can also be used to feed water-based fertilizers directly into the soil, often deploying it deeper beneath the topsoil so it will begin more integrated than fertilizers applied via top- or side-dressing. Mixing the soil additives by hand is still useful for your plants, and using tools such as small garden tillers can help deal with other concerns like weeds. Just be aware that not all fertilizers are created equal, so you'll want to figure out which fertilizers supply certain nutrients before jumping straight into the application stage.