Elevating Corn Yield with Incremental Fertility and Hybrid Selection

INSIGHTS

• Incremental application of nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) resulted in a 13.5 Bu/A yield increase across 38 trials over a 4-year period.
• Observed yield responses were related to weather-induced nutrient deficiency correction, enhanced early-season growth, and extended grain fill window.
• Hybrid-specific responses to incremental fertility were characterized through multi-site testing over multiple years.

Introduction

The availability of several key soil nutrients is dictated by weather conditions, especially during periods of emergence and early growth. Initial plant deficiencies can slow early-season growth and development as well as impact yield if they persist into later growth stages. Unfortunately, it is difficult to predict weather-induced nutrient deficiencies until the plant shows symptoms. Supplemental, incremental fertility provides an opportunity to reduce the risk of nutrient loss. It also builds an additional nutrient pool near seedlings that plants can pull from if yield potential and nutrient demand simultaneously increase later in the season.

Understanding how hybrids respond to various management decisions (e.g., seeding rate, fungicide, nitrogen, fertility) helps to match appropriate hybrids to distinct management styles. Golden Harvest conducts annual research trials to analyze how the corn portfolio responds to incremental fertility management.

Testing Responses to Incremental Fertility

Since 2021, the Agronomy in Action research team has tested how incremental fertility impacts individual hybrid performance. These trials have applied 70, 36, 32, 17, and 0.15 lbs N/A, P₂O₅, K₂O, S, and Zn, respectively, through in-furrow, 2×2×2, and surface dribble methods. This approach differs from traditional starter fertilizers like 10-34-0 because individually applied nutrient quantities are high enough to help overcome minor nutrient deficiencies or elevate yield when conditions allow.

Individual hybrids ranging from 80- to 118-day relative maturity (RM) are tested across multiple sites to characterize how Golden Harvest^® hybrids respond to incremental fertility. Specifically, twelve to eighteen hybrids are tested at each location, depending on the RM range. Soil types, soil nutrient status, planting dates, and yield levels vary considerably, thus providing an opportunity to understand how individual hybrids respond to incremental fertility across an array of environmental conditions. Each hybrid is planted into a base and incremental fertility program. The base program consists of the grower’s usual fertility program and is typically designed to support selected yield goals and/or address expected nutrient removal. The incremental program combines the base program with the additional fertility package. It is designed to mimic increased nutrient availability through zone placement practices such as strip-till or banding, not a specific method or timing. This allows for the characterization of hybrid responses to nutrient availability rather than any particular application method or nutrient rates.

Graph 1. Site yield responses to incremental fertility averaged across hybrids, 2021-24 (n = 38).

Value of Incremental Fertility

Across 38 trials conducted in a 4-year period, incremental fertility has resulted in a 13.5 Bu/A response over the base program (Graph 1). Additionally, 82% of the sites exhibited responses greater than 5 Bu/A (31 of 38). Since several nutrients varied in availability across trials, individual location responses were likely driven by a unique nutrient for each trial. For example, early planted sites, such as Slater, IA, in 2024, exhibited greater early-season vigor with the incremental fertility program, presumably from greater plant-available N or P uptake (Figure 1A). Other sites, like Clinton, IL, in 2023 and Janesville, WI, in 2024, experienced S-induced fertilizer responses due to cool spring temperatures slowing soil mineralization (Figure 1B). A third example, Clay Center, KS, in 2024, utilized the additional nutrients placed near the root system to maintain late-season photosynthesis and extend grain fill, resulting in greater yield (Figure 1C).

Figure 1. Increased early season growth (A), sulfur deficiency correction (B), and extended photosynthetic window (C) associated with incremental fertility (right) vs the base program (left).

A common assumption is that incremental fertility management is most valuable in intensively managed, high-yield scenarios. Results from these trials do not support this assumption, however, positive yield responses occurred across a range of yield levels. Specifically, environments with base yield levels of 200 Bu/A or less produced a 28.8 Bu/A response to the incremental fertility treatment (Graph 2). In comparison, yield responses of 11.4 and 8.6 Bu/A were observed with 200-250 and 250+ Bu/A yield levels, respectively. These results indicate that incremental fertility through zone placement may be applicable across various yield environments.

* Indicates yield response averaged across 38 sites, 2021-24.
Graph 2. Yield response to incremental fertility within three different yield levels.

The majority of trial sites had sufficient P and K soil test levels prior to planting, although these sites still experienced positive responses from incremental fertility. Yields increased 14.1 and 13.2 Bu/A at locations with sufficient pre-plant P (20 ppm) and K (175 ppm) levels, respectively (Graph 3). These responses may be better explained by the proximity of the nutrients for uptake rather than the soil test levels themselves. P and K have low mobility in the soil and require root interception or diffusion via water for plant uptake. If root growth is inhibited or soil is dry and diffusion is negatively impacted, plant nutrient uptake can still be affected in soils with sufficient nutrient levels. The incremental fertility treatment used in this trial placed all nutrients except nitrogen belowground and in regions that helped with root interception. Placing concentrated bands of nutrients in areas where root growth occurs increases the likelihood that it will be utilized by the plant.

* Indicates yield response averaged across 38 sites, 2021-24.
Graph 3. Yield response to incremental fertility under sufficient soil test phosphorus (20 ppm) and potassium (175 ppm) levels.

Effect of Incremental Fertility on Grain Moisture

One concern of intensive crop management (e.g., fungicide application) is its potential effect on slower grain dry down. Despite the improved stay green prior to maturity associated with the incremental fertility treatment observed within several hybrids (Figure 1C), it did not result in greater grain moisture. Instead, the inverse occurred with most hybrids, as 80% (20 of 25) of all tested hybrids had lower grain moisture with incremental fertility compared to the base treatment, with an average reduction of 0.39% across all 20 hybrids (range of 0.1 to 1.2%). In some cases, hybrids that had lower grain moisture with incremental fertility also had lower ear placement (Figure 2). There are two theories that may explain this grain moisture reduction. First, increased starch deposition, leading to higher yields, may have replaced water within the kernel,¹ leading to an overall lower water content. Second, the highly available banded nutrients from the fertilizer may have promoted faster, more efficient nutrient uptake that allowed plants to reach physiological maturity sooner than the base treatment where those plants relied more on root growth through nutrient pools located deeper in the soil profile.² The lower ear height was caused by ear initiation on the subsequent lower node. This may be attributed to a more readily available nutrient supply during the early vegetative stages responsible for ear determination promoting fast growth and faster ear initiation, since any nutrient-induced stresses were further minimized with incremental fertility. This faster vegetative growth coincides with academic research that has observed shorter days to silking with starter fertilizer.^2,3

Figure 2. Lower grain moisture (0.5%) and ear placement associated with incremental fertility (left) vs the base program (right) of G03U08 brand at Slater, IA, in 2024.

Hybrid Level Response to Incremental Fertility

Characterizing how individual hybrids respond to incremental fertility helps identify which ones are best suited to intensive management. It is critical that hybrids are tested at many locations across multiple years to ensure that a wide range of environments dictated by soil attributes and weather conditions are represented.

Repeated trials across multiple locations provide a better understanding of how repeatable individual hybrid responses are. Response trends can be used to characterize individual hybrids with response ratings. For example, when comparing G10B61 and G10U97 brands’ responses to incremental fertility across the same trial locations, G10B61 brand responded more often and at a greater magnitude than the average trial response (Graph 4). However, G10U97 brand responded more similarly to the trial average at most locations. Although both hybrids responded to incremental fertility, G10B61 brand appeared to be the more responsive of the two hybrids.

Graph 4. Responses of G10B61 and G10U97 brands to incremental fertility against the overall site average across all hybrids at eight sites in 2024.

Summary

Agronomy in Action Research trials at 38 sites over a four-year period have found that a comprehensive incremental fertility program provided value across a wide range of environments and yield levels. This is related to its ability to correct an array of weather-induced fertility deficiencies as well as provide additional nutrients that can be utilized later in the season if needed. This research also serves as the foundation for understanding the degree of hybrids’ responses to intensive fertility management. By characterizing these responses over a wide range of environments across multiple locations and years, it deepens our understanding of individual hybrid placement and identifies candidates that are well suited for intensive management styles.

References

¹ Saini, H.S. and W.E. Westgate. 2000. Reproductive development in grain crops during drought. Advances in Agronomy 68:59-96.

² Kaiser, D.E., J.A. Coulter, and J.A. Vetsch. 2016. Corn hybrid response to in-furrow starter fertilizer as affected by planting date. Agronomy Journal 108:2493-2501.

³ McGrath, J.M., and B.G. Binford. 2012. Corn response to starter fertilizer with and without AVAIL. Crop Management doi:10.1094/CM-2012-0320-02-RS.