How to Properly Fertilize Corn

Soil Fertility

Just like any crop, soil fertility is a crucial factor in proper corn production. Improper soil pH, nutrient deficiencies and toxicities can all lead to lower corn yields. Ideally, soil intended for corn production should range from level 6 to 7.

Soil with a pH of 5.5 or lower can lead to a variety of problems in fertilizing corn, including:

• Increased aluminum and manganese levels that may stunt growth or kill the plant.
• Decreased availability of nitrogen, sulfur, phosphorus, potassium, calcium and magnesium.
• Limited root growth.
• Insufficient activity from necessary soil microorganisms.

How to Test Your Soil's Fertility

Since low pH can lead to such impactful consequences, you should test your soil's pH so you can address any fertility issues before you begin growing corn. While you should check your soil's pH at least every three years, it wouldn't hurt to run more frequent tests if you can. If you have a yearly rotation of corn, it may be more beneficial to test your soil yearly to verify you have adequate soil fertility.

Testing your soil isn't as easy as grabbing a bit of dirt and sending it off to the lab — OK, it kind of is — but there are some steps you need to take to ensure you collect a quality soil sample:

1. Tools: Always use the proper collection tools when taking a soil sample. Augers and soil probes are recommended for the best quality sample, but a spade and clean buckets can also do the trick.
2. Location: You'll want to grab a variety of samples from different parts of your land. Take samples of upland and bottomland soil, light and dark-colored soil and soil with unique or varying textures. This will give you a full picture of your soil's health, and not just the soil for one small, specific area.
3. Technique: Use a soil map to identify and collect varying soil samples from around your property. Typically, you should aim to make your sample 4 to 6 inches in depth, depending on the type of land.

The Importance of Nitrogen

Corn plants are known to be greedy for nitrogen. Corn typically needs more nitrogen than the air and soil can give. Without supplemental nitrogen, your successful corn yield dreams will be crushed.

Corn plants suffering from a nitrogen deficiency will make this problem known in a few ways:

1. These plants will take on a pale, yellowish-green look.
2. You may notice a yellow inverted V-shaped pattern developing on the tips of older or lower leaves.
3. The corn plant leaves will begin to die in that same inverted-V pattern.

Luckily, this can be avoided with proper nitrogen management. Around 1 pound of nitrogen is needed per expected bushel yield. This can change, depending on the land's location. Nitrogen moves fairly quickly in moist and humid climates. This means some farmland, specifically those with drier, lighter and sandier soil, may be able to use less nitrogen.

Proper soil sampling can help you determine the correct levels for your own farmland.

Causes of Low Nitrogen Levels

Significant amounts of nitrogen loss can continue throughout the growing season, so it's important to add nitrogen supplements at various points of the season routinely. If nitrogen is added all at once, your soil will start off strong but eventually lose considerable amounts of nitrogen throughout the growing process — leaving you with corn yield loss.

Nitrogen levels can decrease for a few different reasons, including:

• Denitrification: Denitrification occurs in soil with water-logged anaerobic conditions due to poorly drained soil or areas that experience excessive rainfall.
• Leaching: Leaching is most common in soils with low cation exchange capacity (CEC). These soils also tend to have a sandy texture and experience high rainfall.
• Runoff: Another cause of nitrogen loss is runoff, where nitrogen and other nutrients are physically carried away by excess water draining into waterways.
• Volatilization: This type of nitrogen loss typically occurs in hot and humid climates and in soils with a pH higher than 7.

Since a lot of nitrogen loss comes from excessive rainfall and moisture, it's crucial to have well-draining soil. In fact, well-drained soil is a crucial corn-growing condition for maximum growth and yield.