How Much Rain is Too Much After Fertilizing the Lawn?

Last updated on November 20, 2020

The short answer is no more than half an inch in 24 hours. The details are explained below. Read on to find out how to time your lawn fertilizing as well.

Sometimes gardens, plants, and vegetation need a little bit of help to grow. The nutrients in the soil can be deficient and fertilizer must be used.

Fertilizer is fairly routinely used for lawns and gardens, particularly when growing vegetables or flowers that are not native to the region. Though a common practice among lawn care experts, there are many variables to consider when fertilizing.

Climate and weather, soil type, and geographic locations are importing to consider prior to fertilizing. Fertilizer does need to be watered into the ground, however, too much water can wash away the nutrients, making the fertilizer less effective. 

Timing your fertilization perfectly can make the most of it. However, not checking and considering the weather can render your fertilizer useless and a waste of valuable time and money.

So how much water is too much and what can be done about it? 

What's Inside?

Timing

sprouting grass

When to fertilize is an important question. Fertilizing at the wrong time, or providing too much fertilizer can result in weed growth or even burning the lawn or crops. 

It’s generally recommended that fertilizer be applied around the time that grass and vegetation are actively growing. This may vary depending on geographic location but is often between February and April.

Once the season has been selected, it is time to look at the weather. 

Fertilizing after heavy rainfall isn’t typically recommended. The wet ground may help the nutrients to spread, however, it will not  “water in” the fertilizer the same way and may prevent the nutrients from entering at the roots where it is most effective. 

If one chooses to fertilize after heavy rainfall, it is typically best to wait until the grass is dry, or at least two days, after a heavy rainfall before fertilizing. 

It is also worth noting that even if the ground is wet, watering after fertilizing will still be necessary. Watering already saturated ground may not be effective when fertilizing. 

It’s a common belief that fertilizing before a heavy rainfall is the best. The assumption being that the rainfall will help to “water in” the fertilizer. While this may be true, there are other considerations to be made as well.

Fertilizing before a rainfall may mean too much water. As with all aspects of gardening and lawn care, the right balance of water is needed. 

Heavy rainfall may wash away the fertilizer, preventing it from ever entering the soil and therefore not providing necessary nutrients to plants and grass. 

It is also possible for heavy rainfall to wash the fertilizer into other water, potentially polluting public water sources.

How Much is Too Much?

rainfall on grass

After fertilizing, a little bit of water will be required within 24 hours, generally no more than half an inch. After that, it is best to allow the ground to sit for at least 2 days. 

Many different types of fertilizers require constant levels of moisture for several days or weeks, be sure that upcoming rainfall will be sufficient to maintain appropriate levels of moisture. 

If you decide to allow nature to take care of “watering in” the fertilizer, it will take some planning. Too little rain will not effectively spread the nutrients, but too much could wash it all away and be a potential hazard to other water sources. 

In general, if you do not want to water using an irrigation or sprinkler system, it is best to fertilize before rain is expected, not after. However, if rainfall is expected to be heavy or lasts more than a day, it may be best to hold off on the fertilizer. 

It is also important that the water within the first 24 hours be evenly distributed. This means that if there are areas that are prone to flooding, or that are on higher ground, rain alone may not be enough to effectively spread the nutrients. 

More than half an inch of rain can increase the risk of washing away the fertilizer and draining dangerously into sensitive areas, less may not be effective in settling the fertilizer. 

Overall it is best to fertilize two days before rain is expected, provided it is average rainfall. 

Other Considerations

sprinkler

If chancing the rain seems too risky there are other options to consider. Irrigation and sprinklers can offer the correct amount of rain and can typically ensure that the water is evenly spread. 

Another thing to consider is the composition of the soil. Soil that is a little more sandy may have a very different response to heavy rainfall with fertilizer washing away quickly. In comparison, thicker soil will be able to withstand and absorb heavy amounts of rain. 

While the amount of rain that will fall in the days after fertilization is important, sunlight should also be considered. When checking the weather, ensure that there will be adequate sunlight expected in the 2-3 days that follow. 

Instructions

types of fertilizer

While it may seem fairly straightforward, it is always best to consult the instructions on the fertilizer being used. 

The amount of water may be different depending on the composition of the fertilizer, the time of year, geographic location, and the vegetation being grown. 

Be sure to consider the possibility of runoff and potential for pollution regardless, but when in doubt regarding when to fertilize or how much water is needed, it is best to rely on the instructions.

Fertilizing is common and often necessary for growing and maintaining a thriving garden.  Fertilizing can also be quite an investment of time and money, as such, it is important that the timing be efficient.

Considering the amount of rain and sun expected, the composition of the soil and the potential for contamination and runoff can ensure that fertilizing is both effective and safe for the environment. 

Too much rain may wash away the fertilizer before it can be absorbed at the roots, where it is most needed. Like all aspects of gardening and lawn care, it is imperative to have the right balance of water and sun for your lawn to thrive. 

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