My favorite part of the research experience so far has been sharing what I'm doing with other people. We've sparked a lot of curiosity and questions with corn tiller content on my social media platforms! Seeing the #TillerQueen mentions and tags in corn anomalies/tiller pictures is BEYOND cool.
But what exactly are we up to in these corn fields?
I'm SO glad you asked. This post is for you!
This project was created in a joint collaboration between my major professor, Dr. Ignacio Ciampitti (Farming Systems Professor, Deparment of Agronomy, Kansas State University), and Research and Development leads at Corteva Agriscience/Pioneer. Funding is coming from Corteva Agriscience, Kansas Corn, and the Kansas State University College of Agriculture.
The goal? To understand the impact and plasticity potential of tillers in low population density corn fields - including a look at biomass, yields, and yield components. Experiments for this project began in 2019, and 2021 will be our third and final (planned) summer of field studies.
How are we testing the "impact of tillers"?
Our team is using field studies in an attempt to realistically understand how tillers can affect yields and biomass in low population density fields. In this pursuit, we have 12 treatments. Each treatment represents a different scenario we are testing for our corn plots, and our treatments are each made of 3 different factors. Each factor is a specific piece of the puzzle we are changing between plots. The different versions of each factor are called levels.
Factor 1: Density
Levels: 24,000 plants/acre 17,000 plants/acre 10,000 plants/acre
Factor 2: Genotype (Hybrid)
Levels: Pioneer P0657AM Pioneer P0805AM
Factor 3: Tiller Presence
Levels: Tillers removed at stage V10 Tillers intact
From these 3 factors, our 12 treatments are created with all possible combinations of each factor's levels (called a "factorial" treatment structure, giving us 3 Densities x 2 Hybrids x 2 Tiller Levels = 12 unique treatments)
24,000 plants/acre || Pioneer P0657AM || Tillers removed at stage V10
24,000 plants/acre || Pioneer P0657AM || Tillers intact
24,000 plants/acre || Pioneer P0805AM || Tillers removed at stage V10
24,000 plants/acre || Pioneer P0805AM || Tillers intact
17,000 plants/acre || Pioneer P0657AM || Tillers removed at stage V10
17,000 plants/acre || Pioneer P0657AM || Tillers intact
17,000 plants/acre || Pioneer P0805AM || Tillers removed at stage V10
17,000 plants/acre || Pioneer P0805AM || Tillers intact
10,000 plants/acre || Pioneer P0657AM || Tillers removed at stage V10
10,000 plants/acre || Pioneer P0657AM || Tillers intact
10,000 plants/acre || Pioneer P0805AM || Tillers removed at stage V10
10,000 plants/acre || Pioneer P0805AM || Tillers intact
Now that we have our treatments, the most important point here is how we're making sure the testing is "fair". To help with this, we use an EXPERIMENTAL DESIGN and blocks.
Experimental designs and blocking help us do a better job of making sure that the response we're seeing is ACTUALLY coming from the treatments we are applying (NOT due to better soil in one part of the field or turkeys/deer munching on one of our plots). The experimental design we are using for this project is called a split-split-plot design, with complete blocks.
That is, each of our 12 treatments shown above are found in 3 different plots at each location - 1 in each of our 3 BLOCKS. Our blocks are complete groups containing 1 plot from each of the 12 treatments. Inside each block, our treatments are initially grouped based on Density (called the "whole plot"), then grouped based on Hybrid within Density (called the "sub-plot"), and finally, Tiller level is randomly assigned within each Hybrid x Density combination (called the "sub-sub-plot").
These designs are difficult to understand sometimes, so here's a visual to help.
Because Tiller Level is the smallest grouping, each "O" and "X" represent one plot, and the colored layers show the density and hybrid of that plot. For example, all plots shaded with the dark ovals are the treatment 10,000 plants/acre || Pioneer P0805AM || Tillers removed because they are in the light green density group, in the light hybrid group, and they are labelled with an "X". All plots highlighted with light ovals are the treatment 17,000 plants/acre || Pioneer P0657AM || Tillers intact because they are in the medium green density group, in the dark hybrid group, and they are labelled with an "O".
Inside each grouping (Block, Whole Plot, Sub-Plot, and Sub-Sub-Plot), treatments are randomly organized, but the grouping we used forces some organization for where plots are located. For example, our blocks ensure that all 3 plots with the same treatment are not planted in a bad part of the field. Notice how each of the treatments highlighted above are separated across the field - never always in one corner or even on the same east/west side! If we have a very uniform field for our research plots, this strict structure becomes less important, and we can be more random in our plot placement.
What are we measuring and why?
At 5 time points throughout the season (V5, V10, V16, R3, & R6), we will be taking biomass measurements, which tell us how much the plants are growing and how healthy they are. This will be collected from a 5-foot section of our plots and scaled up to acres and hectares. This may seem like a big jump, but because we have three unique plots with the same treatment, this gives us more confidence in our numbers.
We will be measuring rows and counting plants to get exact stands, in addition to making sure each density fits the target we were intending (10,000 , 17,000, and 24,000 plants/acre). In addition to the number of plants, we will be taking notes on how many tillers we have in each plot, when they are appearing, and where on the plant they are growing from (specifically, which node).
At the close of the season (R6 or "physiological maturity"), we will be harvesting each plot by hand, separating main plant ears and tiller ears, and further separating tiller ears into tiller lateral ("normal" or "axillary") ears and tiller tassel ("apical") ears. After shelling these ears, we'll be able to scale up yields to acres and hectares based on grain weight, grain moisture, and harvest area.
More to come on all of these and the process of collecting this data as the season progresses!
How do we know our results are relevant?
To make sure we're being as general as possible with the results we are reporting (that is, not JUST reliable in ONE location with the unique field conditions we experienced in ONE year), we are applying these treatments to corn plots across the state for 3 years of data collection. The sites we've had since 2019 are listed below:
Manhattan, KS (2019)
Garden City, KS (2019, 2020, 2021)
Goodland, KS (2019, 2020, 2021)
Colby, KS (2019, 2020, 2021)
Keats, KS (2020, 2021)
Buhler, KS (2020, 2021)
Greensburg, KS (2020, 2021)
Selkirk, KS (2021)
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