Corn yields in the U.S. have improved over time, as steady gains have been made in genetic yield potential, plant protection technologies and tolerance to stresses. However, typical observed corn yields are only a fraction of the maximum yield potential of today’s corn hybrids, and only with adequate environmental conditions and agronomic management can growers increase yields or minimize the potential for yield loss. There is a need for a better understanding of which agronomic management practices have the greatest impact on corn yield and how these practices interact. Therefore, the Crop Physiology Laboratory at the University of Illinois set out to:
- Demonstrate the potential for yield improvement with enhanced crop management.
- Quantify the impact of different management factors on corn yield.
- Determine the synergisms of these factors when combined together in an agronomic system.
Agronomic Management Systems
In 6 environments in IL from 2014-2018, 5 management factors were assessed for their individual and cumulative impact on corn grain yield under corn-soybean rotation and conventional tillage. The 5 agronomic management factors considered were:
- Fertility to include phosphorus (P), potassium (K), sulfur (S), zinc (Zn) and boron (B)
- Nitrogen (N) fertility
- Plant population
- Foliar fungicide
- Row spacing
Each factor consisted of 2 levels representing either the “Standard” or “Enhanced” system (Table 1). For the first factor, no added fertility, based on adequate soil test values, was applied in the standard system. MicroEssentials-SZ [12-40-0-10(S)-1(Zn)] was banded 4-6” beneath the future crop row for 100 lbs P2O5, 25 lbs S and 2.5 lbs Zn/A and Aspire [0-0-58-0.5(B)] was broadcast applied with light incorporation for 75 lbs K2O and 0.6 lbs B/A in the enhanced system. Nitrogen was broadcast applied in the spring as UAN for 180 lbs N/A with the enhanced level receiving an additional 60 lbs N/A sidedressed at V6. Target final plant stands were 32,000 and 44,000 plants/A in the standard and enhanced systems, respectively.
To determine the influence of fungicide on plant health and yield, the enhanced system received a foliar application of Quilt Xcel® or Trivapro® at flowering (VT/R1) while the standard system received none. The trial was planted in both 30” and 20” rows with the narrower spacing considered the enhanced practice. The best “racehorse” hybrid was chosen for each environment with the goal of maximizing yield responses to the enhanced management factors (Table 2).
With all enhanced factors combined as an agronomic package and compared to the standard system, corn grain yield increased by an average of 52 bu/A (+25%) across the 6 environments and ranged from 36-65 bu/A (+19-35%) (Table 2). These yield improvements can be attributed to maximizing early-season light interception through narrower row spacing and higher plant density, providing season-long nutrition and lengthening photosynthetic duration with fungicide application. Additionally, the yield level in both the standard and enhanced systems tended to increase from 2014-2018, which is likely attributed, in part, to improved plant genetics and hybrid selection.
Most Important Factors
To determine the individual and combined impact of each management factor, an addition/omission treatment structure was used (Table 3). Additionally, the fertility factor was evaluated in three components: Banded P-S-Zn, Broadcast K-B and both. 7 additional treatments (+Band P-S-Zn, +Broad K-B, +P-S-Zn and K-B, +N Sidedress, +Population, and +Fungicide) were implemented by individually substituting the enhanced level of each management factor while all other management factors were maintained at the standard level (Table 3).
Similarly, 6 omission treatments (-Band P-S-Zn, -Broad K-B, -P-S-Zn & K-B, -N Sidedress, -Population, and -Fungicide) were implemented by individually substituting the standard level of the factor while maintaining all other factors at the enhanced level. In this way, the value of each management factor was tested at the standard level of agronomic management in an enhanced management system.
While the Crop Physiology Laboratory has demonstrated positive yield responses to narrower row spacing in this study, responses to narrow rows can be mixed in commercial settings and are especially dependent on the hybrid used. Thus, the addition/omission results from this study have been averaged over both row spacings (Table 4).
The management factor that had the greatest impact on yield in both the standard and enhanced systems was fertility (Table 4). The addition of banded P-S-Zn and broadcast K-B in the standard system increased yield by 11 bu/A (+5%) while its omission from the enhanced system decreased yield by 16 bu/A (-6%). Most of the impact on yield was from the P-S-Zn, as K-B had no effect on yield when added to the standard system alone (Table 4). The influence of added fertility was most notable in the high-population, high-input system, which required the greatest availability of nutrients to maximize yields.
Averaged over the 6 environments, the supplemental 60 lbs N/A sidedressed over the base rate of 180 lbs/A increased yield by 7 bu/A (+3%) when added to the standard system and decreased yield by 9 bu/A (-4%) when omitted from the enhanced system (Table 4). As N availability is highly influenced by the weather, supplemental N had a greater impact on yield in environments with weather conducive to N loss (data not shown). Like other nutrients, N fertilization was more important in the enhanced system.
Significant yield increases with the enhanced system over the standard system indicate that the environments tested in this study could support plant populations greater than 32,000 plants/A (Table 2). However, increasing plant population from 32,000 to 44,000 plants/A decreased yield by 8 bu/A (-4%) in the standard system. Decreasing from the high density to the lower density in the enhanced system had a minimal, but negative, impact on yield (Table 4). Therefore, increasing plant population without adequate plant nutrition and fungicide (i.e., standard system) can decrease yield.
Response to fungicide is like N. It is highly influenced by the environment, especially by weather conditions conducive to disease development. Thus, when averaged across environments, the addition of fungicide to the standard system did not significantly affect yield (Table 4). However, removing fungicide from the enhanced system reduced yield by 9 bu/A (-4%).
Management Factors Work Together
If combinations of agronomic factors acted additively, all of the individual yield values for the added factors over the standard control would amount to a yield increase of 14 bu/A. This is the sum (in bu/A) of +11 from fertility, +7 from sidedress N, -8 from increased plant population, and +4 from fungicide (Table 4). However, the actual yield response of all factors combined averaged across environments and row spacing was 34 bu /A (difference between the enhanced and standard control treatments), which is substantially greater than the summation of all individual added factor contributions (Table 4). Therefore, combining these enhanced management factors synergistically led to a 20 bu/A yield boost.
Notably, the impact on yield from one management factor is dependent on the other factors present in the system. Generally, yield reduction resulting from omitting a factor from the enhanced system was greater than the yield increase from adding that factor to the standard control (Table 4). When considering managing corn for greater yields, a comprehensive systems approach will often increase yield more than the increase from enhancing any one management factor alone.
For more information corn management and yield potential, contact your local Golden Harvest Seed Advisor.
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