Management Yield Potential-Racehorse or Workhorse?

A system for characterizing a corn hybrid’s responsiveness to agronomic management

 

 

• Why MYP?
• 'Workhorse' hybrids
• 'Racehorse' hybrids
• 2015 Experimental design

• Results of the 2015 MYP trial
  (for 2016 report, download the .pdf here [1 MB])

• How to participate

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Why Management Yield Potential (MYP)?

Do you ‘shoot for the stars’ for highest yield, or play it more cautiously? Do you take an offensive or defensive approach when it comes to your production management style? Do you have some prime land that you want to push to the limits, or some less- than perfect land, that you’re looking to plant to a stable hybrid?

 It is important to understand the characteristics of corn hybrids and their yield response to different crop management factors in order to maximize productivity on your farm. Our laboratory has aimed to characterize current commercial corn hybrids and their potential yield under different crop management dynamics, namely, their Management Yield Potential.

The Management Yield Potential (MYP) project aims to identify ‘Racehorse’ hybrids, or hybrids with adaptability to high yield environments (e.g, responsive to crop management), and ‘Workhorse’ hybrids, or hybrids with acceptable yields in a low fertility environment (e.g. tolerant to N loss).

 

 

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'Workhorse' hybrids

Workhorses are those that are reliable under a wide range of conditions, they may not be flashy, but they’ll get the job done under a wide range of circumstances. Where there’s less- than- perfect fields in less- than- perfect weather conditions, these hybrids will still have a decent yield. Of all the factors that can be managed, the availability of nitrogen (N) fertilizer has the greatest impact on corn yield. But even if you fertilize with an adequate amount of N, droughts or excessive rain may reduce how much N is available to the plant. Therefore, we have classified ‘Workhorse’ hybrids as ones having an above- average Check Plot (yield at 0 lb N acre^-1) and a high initial response to N (InitN, yield increase between 0 and 60 lb N acre^-1 at 32,000 plants acre^-1). These two factors are the most important for determining a hybrid’s yield stability over a range of production conditions. An example is shown in Figure 1.

 

Figure 1. Identifying workhorse hybrids as those having both an above- average yield with no N fertilizer, and above- average yield increase when provided 60 lb N/ acre. Data points are from 42 commercial hybrids grown in 2014 at Champaign, IL. Figure adapted from Mastrodomenico and Below 2015.

 

 

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'Racehorse' hybrids

While defining a workhorse hybrid is straightforward, characterization of ‘Racehorse’ hybrids is more complex (Fig. 2). Racehorses are hybrids that can be pushed to their maximum yield with proper management of fertility, population, and row spacing. To achieve greater yields, it may be necessary to use narrower rows in combination with more plants per acre (Fig. 3). In 2015, we developed a new approach to estimate the ‘Racehorse’ index of a hybrid, including yield changes in response to variation in nitrogen supply, plant population, and row spacing.

 

In 2015, we described 43 commercial hybrids from Channel, Croplan, DeKalb, Golden Harvest, Pioneer, and Stone for Workhorse and Racehorse potential, including yield response characterizations for:

• Narrower row spacing (20” vs 30”) at high populations (44,000 plants/ acre)
• Max Population
• Intermediate Population
• Maximum Nitrogen
• Initial Nitrogen
• Check Plot

 

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2015 Experimental design (for 2016 report, download the .pdf here [1 MB])

 

43 commercial hybrids: representing six seed brands and ranging from 104 to 117 day maturity (Table 1).

3 locations: DeKalb, IL (41^o55’N, 88^o45’W), Champaign, IL (40o06’N, 88^o16’W), and Harrisburg, IL (37^o44’N, 88^o32’W).

4 replications in a split-plot design

6 management treatments:

1. 32,000 plants acre^-1 at 30-inch row spacing and 0 lb N acre^-1,
2. 32,000 plants acre^-1 at 30-inch row spacing and 60 lb N acre^-1,
3. 32,000 plants acre^-1 at 30-inch row spacing and 280 lb N acre^-1,
4. 38,000 plants acre^-1 at 30-inch row spacing and 280 lb N acre^-1,
5. 44,000 plants acre^-1 at 30-inch row spacing and 280 lb N acre ^-1, and
6. 44,000 plants acre^-1 at 20-inch row spacing and 280 lb N acre ^-1.

At maturity, plots were harvested with a two-row plot combine and grain yield is reported as bushels acre^-1 at 15.5% moisture concentration.

Racehorse and Workhorse indices calculations:

 

To determine the Racehorse index for each hybrid, we calculated the following parameters within each location:

Maximum yield Response to N (RTN, yield change between 0 and 280 lb N acre^-1 at 32,000 plants acre^-1),

Intermediate Plant Population (IntRTP, yield change between 32,000 and 38,000 plants acre^-1 at 280 lb N acre^-1),

a Maximum yield response to Plant Population (MaxRTP, yield change between 38,000 and 44,000 plants acre^-1 at 280 lb N acre^-1), and the yield response to

Narrower Row Spacing (RTR, yield change between 30 and 20 inch row spacing at 44,000 plants acre^-1 and 280 lb N acre^-1).

In contrast, ‘Workhorse’ hybrids are characterized by an index, which includes:

Check Plot (yield at 0 lb N acre^-1), and

Initial response to N (InitN, yield increase between 0 and 60 lb N acre^-1 at 32,000 plants acre^-1).

Each parameter, hybrid, and location were ranked, and scored with 1 being the least (or most negative) yield change, and 10 the greatest yield increase.

 

 

2015 Results below (for 2016 report, download the .pdf here [1 MB])

For all measured parameters at all locations, there was a large range in yield responses to the imposed management, from yield losses to yield increases. The Champaign and Harrisburg sites promoted similar responses to populations and row spacing between hybrids, but not similar rankings among hybrids from those management factors. At DeKalb, a population of 44,000 plants/ acre more often than not decreased yield, regardless of row spacing.

 

The range in yield response of the hybrids to population and row spacing at the three locations in 2015 is shown in Figs. 4-6. All parameters were arranged in a similar manner per location, then scored for the index, with 1 being the least (or most negative) yield change, and 10 the greatest yield increase.

Figure 4. Yield response to different agronomic management practices for intermediate yield response to population (IntRTP, yield response between 32,000 and 38,000 plants acre^-1 at 280 lb N acre^-1), maximum yield response to plant population (MaxRTP, yield response between 38,000 and 44,000 plants acre^-1 at 280 lb N acre^-1), and yield response to narrower row spacing (RTR, yield response between 30 and 20 inches row spacing at 44,000 plants acre^-1 and 280 lb N acre^-1) at Champaign, IL. 

 

Figure 5. Yield response to different agronomic management practices for intermediate yield response to population (IntRTP, yield response between 32,000 and 38,000 plants acre^-1 at 280 lb N acre^-1), maximum yield response to plant population (MaxRTP, yield response between 38,000 and 44,000 plants acre^-1 at 280 lb N acre^-1), and the yield response to narrower row spacing (RTR, yield response between 30 and 20 inches row spacing at 44,000 plants acre^-1 and 280 lb N acre^-1) at DeKalb, IL.

 

Figure 6. Yield response to different agronomic management practices for intermediate yield response to population (IntRTP, yield response between 32,000 and 38,000 plants acre^-1 at 280 lb N acre^-1), maximum yield response to plant population (MaxRTP, yield response between 38,000 and 44,000 plants acre^-1 at 280 lb N acre^-1), and the yield response to narrower row spacing (RTR, yield response between 30 and 20 inches row spacing at 44,000 plants acre^-1 and 280 lb N acre^-1) at Harrisburg, IL

 

Characterization of ‘Workhorse’ and ‘Racehorse’ Hybrids

Commercial hybrids vary widely for their tolerance to low N, yield response to N fertilizer, row spacing, and optimal plant population. Grain yield was also highly affected by location, which interacted with the other agronomic factors. The lowest yield under low N conditions and the highest yield response to N fertilizer were obtained at Harrisburg, IL. In addition to check plot and N response, Harrisburg also exhibited the largest response to plant population and to narrower row spacing. The largest grain yield was obtained with 44,000 plants acre^-1, 280 lb N acre^-1 and 20-inch row spacing at Champaign, IL (average of 282.9 bu acre^-1) and Harrisburg, IL (average of 239.3 bu acre^-1), and with 32,000 plants acre^-1, 280 lb N acre^-1 and 30-inch row spacing at DeKalb, IL (average of 226.6 bu acre^-1). Heavy rainfall during mid-June may have decreased the yield response to most agronomic factors evaluated at DeKalb, IL.

The evaluation of crop responses to different agronomic factors gives growers and agronomists the opportunity to better position their hybrids and obtain the maximum yield potential of the hybrid using the recommended agricultural management. Typical variety testing methods using ‘standard’ agronomic conditions (e.g., 280 kg N ha^-1 at 32,000 plants acre^-1) are used to determine a hybrid’s yield potential, but do not provide information regarding a hybrid’s responses to N loss, increased plant population, or narrower row spacing. Intensive crop management practices are necessary in order to decrease the current corn yield gap existing in the U.S Corn Belt (Ruffo et al., 2015). Nonetheless, hybrid selection based on agronomic management performance is a key component to the success of intensive farming practices.

The MYP trial identifies the impact on yield from the most important agronomic factors (e.g. N rate, hybrid selection, plant population, and row spacing) and uses the yield responses to characterize corn hybrids based on their tolerance to N loss (‘Workhorse’) and response to intensive crop management systems (‘Racehorse’). We have evaluated the genotypic and phenotypic variance and covariance from each agronomic factor to estimate the ‘Racehorse’ and ‘Workhorse’ indices. This approach takes in consideration environmental effects and the correlation of the different agronomic factors. Our objective is to develop indices that identify the agronomic characteristics of a hybrid due to its genetic effects. Using multivariate analysis, the relative weights of the parameters for this trial were

‘Racehorse index’ = 0.02 IntRTP + 0.004 Max RTP + 0.48 RTN + 0.48 RTR

(that is, 48% of the Racehorse (high yield potential) index is due to the response to N fertilizer and 48% due to the response to 20” row spacing.)

‘Workhorse index’ = 0.35 Check Plot + 0.64 InitN

(35% of the Workhorse (stable yield potential) index is can be estimated by the yield at 0 lb N/acre, and 64% by the yield increase between 0 and 60 lb N/ acre.

‘Workhorse’ and ‘Racehorse’ indices and the scores for each hybrid across locations are represented on Tables 2 and 3. 

   

Table 2. Check plot scores (yield at 0 lb N acre^-1), initial N response scores (InitN, yield response between 0 and 60 lb N acre^-1 at 32,000 plants acre^-1), and ‘Workhorse’ indices (WHI) at Champaign, DeKalb, and Harrisburg, IL in 2015.

 

 

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How can seed companies participate in the Management Yield Potential trial?

Beginning in 2016, the University of Illinois Crop Physiology Laboratory may be able to offer the Management Yield Potential trial to seed companies as a fee-based hybrid characterization service. Our research sites are located at Harrisburg (Saline County), Champaign (Champaign County), and DeKalb (DeKalb County). The treatments that we use to characterize hybrids consist of three nitrogen rates (0, 60, and 280 lb N/acre) and three plant densities (32,000, 38,000, and 44,000 plants/acre). The nitrogen treatments allow for the check plot yield (i.e., low nitrogen tolerance at 0 lb N/acre) and initial and maximum responses to fertilizer nitrogen. Four replications are planted at each location using a variable population plot planter. For more information on entering hybrids in the MYP trial, please contact Dr. Fred Below.

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Related documents and links

1. 2015 Management Yield Potential trial report [PDF, 4 MB]
2. Becker, R. 2012. Management of higher populations in maize. University of Illinois at Urbana-Champaign MS thesis. [link to abstract and PDF]
3. Haegele, J.W. 2012. Genetic and agronomic approaches to improving nitrogen use and maize productivity. University of Illinois at Urbana-Champaign PhD dissertation. [link to abstract and PDF]
4. Mastrodomenico, A.T. and F.E. Below. 2015. Characterizing corn hybrids for their response to management. University of Illinois Agronomy Day. 20 August. Urbana, IL [.pdf 1.86 MB]
5. 2016 Management Yield Potential trial report [PDF, 1 MB]

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