Skip to Main Content

Corn Root Damage Caused by Fertilizer

Many farmers in Indiana utilize starter fertilizer applications, specifically applied through the planter and in close proximity to the seed, which are known to provide benefits such as early crop access to necessary nutrients, improved and more rapid plant growth, and reduced grain moisture at harvest. However, placing fertilizer close to the seed at planting can increase the potential for root damage and poor crop establishment, especially when improper products and/or rates are used. In addition, these risks can be exacerbated in coarser soil textures and in drier soil conditions that follow planting.

Damage caused by starter fertilizer applications can typically be identified by examining the roots of a corn plant, especially if there are areas of a field with noticeable stand establishment and/or stand loss issues. Most starter fertilizer damage observed can be attributed to in-furrow, or pop-up fertilizer applications due to fertilizer being placed directly on the seed. However, damage can also occur from 2x2 starter fertilizer applications and from pre-plant anhydrous and urea applications if too high of rates, shallow injection depth, and/or dry conditions at planting are observed. Yet, these application methods can greatly reduce the risk of potential injury as compared to an in-furrow application. Starter fertilizer damage is often most noticeable from a damaged radicle (the first root that emerges from the seed as it develops; Figures 1 and 2). The radicle will typically be short and brown/black in color and almost looks like someone may have taken a lighter to it. In addition, significant damage to the mesocotyl (white, root-like tissue between the seed and the base of the plant) can also occur from excessive starter fertilizer rates (Figure 3).

Corn root damage caused by starter fertilizer is often attributed to the salt content present in fertilizers and the fertilizer salt index is often used to promote and sell safer in-furrow options. However, ammonia formation in the rooting zone from urea-based fertilizers can also contribute to these observed issues. For example, when high rates of nitrogen are applied close to the seed and rooting zone, ammonia can form and result in injury to the roots. Both the risk of injury from ammonia formation and the risk of salt injury are typically why it is important to limit the amount of N + K2O applied in a starter application. However, potassium is typically not recommended in a starter fertilizer application unless soil test levels are low (<70 ppm).

According to the Tri-State Fertilizer recommendations (https://agcrops.osu.edu/FertilityResources/tri-state_info), starter fertilizer applications are less risky when applied in a 2x2 application and rates should range from 20 – 40 lbs per acre of N, P2O5, and K2O and should not exceed a rate of 100 lbs per acre of salt fertilizers (N + K2O). As for in-furrow applications of fertilizers, salt fertilizer (N + K2O) should not exceed 8 lbs per acre on heavier soils and 5 lbs per acre on sandier soils (<5 CEC). In addition, it is also important to avoid the use of thiosulfate products (e.g, ATS) applied in-furrow due to potential seed germination issues.

starterdamage2.png

Figure 1. Corn radicle damage caused by excessively high in-furrow nitrogen fertilizer application. NW Indiana, 2022.

starterdamage1.png

Figure 2. Corn radicle damage caused by excessively high pre-plant N fertilizer application combined with dry soil conditions. NC Indiana, 2023.

starterdamage3.png

Figure 2. Corn mesocotyl damage caused by excessively high 2x2 N fertilizer application (>100 lbs per acre). E Indiana, 2022.

Featured Stories

Corn Black Layer
Understanding Black Layer Formation in Corn

The use of the term “black layer” is often a universal method among farmers and...

Read More
Corn Cover Crop
Paying Attention to In-Season Nitrogen Timing is Important when following a Rye Cover Crop

Managing and maintaining a high-yielding corn crop following a cereal rye cover crop can often be...

Read More
corn silk
Stalk and Ear Rots: The Importance of Identifying Them Now to Help with Harvest Decisions

It is now time to evaluate fields for any stalk or ear rot symptoms. This will aid in making...

Read More
corn silk
Silk Emergence, Silk Length, and Missing "Butt" Kernels

The process of pollination is one of the most critical periods for grain yield determination in...

Read More
corn silk
Top "Dieback" and Senescence Patterns in Corn

As corn plants progress through grain fill and approach maturity, plant leaves naturally begin to...

Read More
corn haze
How Does Wildfire Smoke Impact Corn Growth?

In recent years, Indiana has experienced an increase in air quality concerns during the summer...

Read More
To Top