Multi-Hybrid Planting: Potential Benefits and Risks

Necessary Conditions

Three conditions are necessary for a multi-hybrid planting strategy to provide a yield advantage.
- There must be significant within-field variation in yield due to environmental or management factors, including landscape topography and other soil variables.
- There must be a difference between hybrids in yield response to the within-field environmental variation.
- The within-field environmental variation must have some degree of spatial predictability so that the right hybrids can be placed in the right areas of the field.
The final condition is the most challenging of the three to meet because of the effects that weather can have in shaping the growing environment in any given season.
Placing a drought-tolerant hybrid, for example, would require having a reasonably good idea at the outset of the growing season where in the field drought stress is likely to be yield limiting.
Since the decision of where to place a hybrid must be made at the start of the season, it requires a prediction of where in the field yield-limiting stress is likely to occur. The success or failure of a multi-hybrid strategy will depend on the accuracy of this prediction.
In general, environments with a high degree of yield variability across the landscape where yield-limiting stress does not vary greatly year-to-year due to weather are most likely to benefit from variable hybrid placement.

Hybrid Strategies

The most common strategy for variable hybrid placement typically involves pairing a hybrid with high yield potential and a hybrid with lower yield potential but a higher level of tolerance to a yield-limiting stress factor expected to be present within the field.
- These designations are often referred to as “offensive” and “defensive” hybrids, or “race-horse” and “work-horse” hybrids.
- The offensive hybrid is assigned to areas of the field expected to be relatively free of a yield-limiting stress factor, where it can maximize yield, and the defensive hybrid is placed in areas where yield-limiting stress is expected, in order to minimize yield reduction associated with it.
This approach assumes an implicit tradeoff between yield potential and stress tolerance, which may or may not be the case depending on the individual hybrid(s).
A given hybrid may be high yielding and also have a high degree of tolerance to a particular yield-limiting factor, in which case the optimal strategy would be to plant the entire field to that hybrid.

Potential Benefits and Risks

Weighing the benefits and risks of deploying a multi-hybrid strategy depends in part upon the default scenario against which it is being compared; i.e., what a grower would likely do if he/she were not varying hybrid placement.
For example, consider a field that is generally very high-yielding but has a few drought-prone spots within it.
- The default scenario in the case would likely be to plant a high yield potential hybrid across the whole field with the understanding that it will perform poorly in some areas.
- A multi-hybrid strategy in this case would involve placing a drought-tolerant hybrid in the drought-prone spots, thereby exchanging top-end yield potential for resilience against yield loss from drought stress in those portions of the field.
- The greatest risk associated with deploying a multi-hybrid strategy in this scenario is if drought stress does not manifest to the extent expected, in which case top-end yield potential will have been sacrificed for no gain.
Conversely, consider a field that is mostly drought-prone but has a few consistently productive areas in it.
- In this case, the default scenario would likely be to plant a drought-tolerant hybrid across the whole field.
- The multi-hybrid strategy would provide the opportunity to capture additional value by placing a higher yield potential hybrid in the highly productive spots.
- The greatest risk associated with the multi-hybrid strategy would be if the spots expected to be high-yielding instead experience drought stress, in which case the attempt to achieve greater yield would result in lower yield than if the whole field had been planted to the drought-tolerant hybrid.
Simplified examples showing different possible yield outcomes in both of these scenarios are shown below.

Multi-Hybrid Yield Scenarios

Figure 1A: High Productivity Field

Primarily high-productivity field planted entirely to a high yield potential hybrid, yield results. — **(.3 x 160 bu/acre) + (.7 x 240 bu/acre) = 216 bu/acre**

Primarily high-productivity field planted entirely to a high yield potential hybrid, producing a whole-field average yield of 216 bu/acre.

Figure 2A: Drought-Stressed Field

Primarily drought-stressed field planted entirely to a drought-tolerant hybrid, yield results. — **(.3 x 220 bu/acre) + (.7 x 180 bu/acre) = 192 bu/acre**

Primarily drought-stressed field planted entirely to a drought-tolerant hybrid, producing a whole-field average yield of 192 bu/acre.

Figure 1B: High Productivity Field

Primarily high-productivity field with variable hybrid placement, yield results. — **(.3 x 180 bu/acre) + (.7 x 240 bu/acre) = 222 bu/acre**

Primarily high-productivity field with variable hybrid placement. Placing a drought-tolerant hybrid in the drought-stressed zone improves the whole-field average yield to 222 bu/acre, a 6 bu/acre advantage compared to planting the high yield hybrid across the whole field.

Figure 2B: Drought-Stressed Field

Primarily drought-stressed field with variable hybrid placement. Placing a high yield potential hybrid in the high-productivity zone, yield results. — **(.3 x 240 bu/acre) + (.7 x 180 bu/acre) = 198 bu/acre**

Primarily drought-stressed field with variable hybrid placement. Placing a high yield potential hybrid in the high-productivity zone improves the whole-field average yield to 198 bu/acre, a 6 bu/acre advantage compared to planting the drought-tolerant hybrid across the whole field.

Figure 1C: High Productivity Field

Variable hybrid placement does not match field conditions. Placement of the drought-tolerant hybrid in a zone that ends up being highly productive, yield results. — **(.3 x 220 bu/acre) + (.7 x 240 bu/acre) = 234 bu/acre**

Scenario in which variable hybrid placement does not match field conditions. Placement of the drought-tolerant hybrid in a zone that ends up being highly productive results in a 6 bu/acre disadvantage compared to planting the offensive hybrid across the whole field.

Figure 2C: Drought-Stressed Field