Fertilizing is one of the critical elements that keep lawns and gardens healthy and booming. However, proper application of fertilizers, including knowing how and when to water, is very important. Since rain is the most natural way of watering, it makes sense to know how long fertilizer can sit before rainfall.
Although the best time to water fertilizer is immediately after you apply it, you can allow it to sit on your lawn or garden up to 48 hours before it rains. However, if the air temperature is above 85°F (29°C), fertilizers left for over 24 hours can volatilize and burn the grass or plant roots.
The rest of this article will focus on the frequency and conditions for fertilizing and watering, including how to time fertilization with the rain, how often you should water after fertilizing, and the ideal amount of water or rain needed for fertilizers to be effective.
What Is the Best Time to Water After Fertilizing?
When dry fertilizer is applied to the soil, it must be “watered in” so that the nutrients can be dissolved and absorbed by plant roots. So, the best time to water after fertilizing is immediately after spreading it. The longer the fertilizer sits on the soil, the higher the chance of fertilizer burn. Of course, I recommend using a slow-release organic fertilizer (Click to see Amazon listing) to help avoid this issue from ever occurring.
Rain provides even land coverage over the entire lawn or garden. If you’re not expecting rain within a day or two, water the soil thoroughly but not too much, applying at least 1/4 or 1/2 inch (0.7 or 1.3 cm) of water. Spreading fertilizer when the grass or field is still wet can also damage or burn your lawn. Also, if you applied fertilizers with herbicide or weed killer, you must wait until after 24 hours before watering it.
However, if you’re applying liquid fertilizer, it is a different story. The grass or plants must be thoroughly watered with plain water before liquid fertilizer is applied. This helps to prevent fertilizer burn, especially if the soil is dry.
Fertilizing or watering is best done early in the morning, before the air temperature rises, or late in the evening when the atmospheric temperature is typically low. This gives the soil enough time to absorb the material before the full heat of the day. Avoid spreading fertilizer on extremely hot days or during a drought when the soil is seriously lacking moisture.
How Should You Time Fertilization With Rain?
Most people prefer fertilizing before it rains rather than after, but there are advantages and disadvantages to both. What is most important is to know how to properly time your fertilizer application, whether before or after a rain.
Fertilizing Before a Rain
You can spread fertilizer before a rainfall as long as it is expected to be mild or light. Light rainfall a day or two after fertilizing can be a substitute for immediate watering. However, if you’re expecting heavy rainfall, it’s best to fertilize several days before the downpour or wait a few days later.
The danger with fertilizing before heavy or hard rain is that the fertilizer may be washed away before it has a chance to dissolve and be absorbed by plant roots. This is especially true if the land is steep.
Other than washing away your fertilizer, heavy rainfall can also present a danger to the environment. The heavy water can carry the fertilizer into the storm sewer system and contaminate groundwater, springs, lakes, rivers, and other bodies of water nearby.
Such contamination can have a drastic impact on the creatures and plants close to these bodies of water.
Fertilizing After a Rain
From an environmental standpoint, fertilizing after rain is the better option. There is no danger of the fertilizer being washed away, and the soil would be in good condition to distribute the fertilizer to grass or plant roots.
Before spreading your fertilizer, wait until the grass blades or plant leaves are dry. Follow up with a light, thorough sprinkling of 1/4 or 1/2 inch of water immediately after applying the fertilizer. This will help the fertilizer to dissolve and distribute properly into the soil.
How Often Should You Water After Fertilizing?
Asides from the initial fertilizer watering in, the soil must be carefully and regularly watered to keep the grass or plants healthy. The timing and frequency of watering both depend on the type of soil, type of plants, and the season or weather.
After the initial watering in of your fertilizer, wait at least 2 to 3 days before watering again. This allows the roots of the plants to properly absorb the nutrients from the fertilizer. Here are some guidelines on how to water in different seasons.
During the summer, lawns need to be soaked to a depth of 4 to 6 inches (10 to 15 cm) per week. This requires at least one-inch (2.5 cm) of water per week to reach deep into the roots of the grass. Some types of grass require only 2 1/4 inches (0.7 cm) of water during hot or dry weather.
Let your lawn dry out before the next watering. If your grass changes from green to brown despite watering, increase the amount of water (but don’t oversaturate) to keep the grasses fresh and green.
Watering Cool-Season Grasses
Cool-Season grasses grow best in moderately cool temperatures of fall and spring. Their growth is slowed down during the summer, and they can even go dormant. In moderate summer conditions, you can still stick to your regular lawn-watering schedule. This is key, keeping soil healthy by watering regularly keeps crabgrass from sprouting up. Also, make sure you have used a good pre-emergent during the Spring.
To keep cool-season grasses green and gorgeous during hot weather, change to a schedule of one-inch (2.5 cm) or 6 to 8 inches (15 to 20 cm) of water per week, including rainfall.
How Much Water or Rain Is Too Much?
Most grasses require 1/4 or 1/2 inch (0.7 or 1.3 cm) of irrigation or rainwater after fertilizer is applied. Light rainfall is about 0.10 inch (0.25 cm) per hour, and moderate rainfall is somewhere around 0.11 to 0.30 inch (0.3 to 0.8 cm) per hour. If you get more than 3 inches (7.6 cm) of rainfall over a day or two, you may have lost most of the nutrients from your fertilizer.
A common sign of overwatering is severely compacted soils. Dying patches can also indicate that your grass is getting too much water. If you walk on the grass and it squishes or feels spongy, that’s another sign. You may also notice an increase in bugs and an accelerated growth of weeds.
If you’re not sure whether your grass is getting enough water, check for wilting leaf blades or color changes from green to brown or bluish-grey color. You can also perform a “footprint” test by walking across your lawn. If the grass doesn’t bounce back after 10 minutes, you need to water it more.
If none of this works, you may have heavily compacted soils. I have this issue since I live in the south which has mostly clay soils. I used a liquid aerator as well as mechanical aeration to solve the issue.
Fertilizer must be watered in after being applied to a lawn or garden. While the best practice is to water in fertilizer immediately after spreading it, you can still wait up to 48 hours before it rains. If you live in a high-temperature environment, you must water the fertilizer in after leaving it on the lawn for 24 hours.
Avoid spreading fertilizer before a heavy rainfall or when the grass is wet. Instead, you can fertilize several days before the rain or a few days later. Generally, your grass and plants need about one inch of rainfall or irrigation water per week to flourish and stay healthy.
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