![]()
Article Request Page ASABE Journal Article Estimated Feasibility of Controlled Corn Seed Orientation
Edwin Coleman1,2, Courtney Bir2,*, Randal K. Taylor3, Darian Landolt4, Adrian Koller5
Published in Journal of the ASABE 67(4): 903-908 (doi: 10.13031/ja.15600). Copyright 2024 American Society of Agricultural and Biological Engineers.
1 Oklahoma State University, Stillwater, Oklahoma, USA.
2 Department of Agricultural Economics, Oklahoma State University, Stillwater, Oklahoma, USA.
3 Department of Biosystems & Agricultural Engineering, Oklahoma State University, Stillwater, Oklahoma, USA.
4 Agronomic Design and Research, CNH Industrial, Oak Brook, Illinois, USA.
5 Lucerne University of Applied Sciences and Arts, Horw, Switzerland.
* Correspondence: courtney.bir@okstate.edu
The authors have paid for open access for this article. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License https://creative commons.org/licenses/by-nc-nd/4.0/
Submitted for review on 22 March 2023 as manuscript number MS 15600; approved for publication as a Research Article by Associate Editor Dr. Lori Duncan and Community Editor Dr. Heping Zhu of the Machinery Systems Community of ASABE on 30 March 2024.
Citation: Coleman, E., Bir, C., Taylor, R. K., Landolt, D., & Koller, A. (2024). Estimated feasibility of controlled corn seed orientation. J. ASABE, 67(4), 903-908. https://doi.org/10.13031/ja.15600
Highlights
- Corn seed orientation at planting leads to symmetrically oriented leaves across rows, increasing grain yields.
- Although increased yield increases revenue, there are additional costs associated with the technology.
- This study compares the financial implications of oriented seed technology to traditional planting.
- For medium- and high-use producers, oriented corn seed technology pays even at a higher cost of technology.
Abstract. Past research has shown that controlled corn seed orientation at planting leads to symmetrically oriented leaves across rows, resulting in increased grain yields. This study determined the financial outcome, in terms of net present value (NPV), of implementing new corn planter technology that allows for corn seed orientation. NPV’s were estimated using stochastic analysis for input prices, yield, and revenue. Additionally, the payback period was calculated. Sensitivity analysis was conducted using potential price points and usage levels for the new corn planter technology. Three producer usage levels were evaluated: 647 ha (low), 971 ha (medium), and 1295 ha (high). All scenarios were analyzed over 5 years. Three potential machine (technology) costs were also evaluated: $32,000, $96,000, and $160,000. The use of oriented corn seed placement technology (OSP) outperformed traditional methods for all usage levels when sold at $32,000. The use of OSP was about equal for the high-usage producer at a price of $96,000. Within the parameters evaluated, some producers would benefit from adopting the oriented corn seed placement technology if the technology was offered at a price of $32,000. This research is of interest to developers and manufacturers interested in developing such technology, as well as researchers considering further evaluation of oriented corn seed placement. Further research is needed to better establish yield benefits and prices for oriented corn seed technology.
Keywords. Corn seed orientation, Corn yield, Cost-benefit analysis, Payback period.Agricultural yields have been rising for decades, defying predictions that the world’s population would outgrow its food supply (The Economist, 2022; USDA, 2022). Such gains stem largely from innovations and scientific advances in crop genetics, chemicals, equipment, and fertilizers. Likewise, past research has shown that controlled leaf orientation in corn production can lead to increased grain yields (Kaufman, 2013; Toler et al., 1999; Torres et al., 2017). Typically, when leaves are symmetrically oriented across rows, light interception is increased, plant populations can be optimized for the environment, and corn grain yields increase (Drouet and Moulia, 1997; Fortin and Pierce, 1996). Symmetrical leaf orientation can be achieved through controlled seed orientation at planting (Torres et al., 2011). Orienting the seed in the soil requires physical control over the seed until the seed finally settles in the furrow.
Planting technology to orient corn seed on a large-scale is being developed on a very limited basis. However, previous studies testing the validity of higher yields from oriented corn seed placement were planted by hand. For instance, Toler et al. (1999) conducted field studies to investigate the interaction of light interception and leaf orientation on corn grain yield. Seed orientation was manipulated to achieve specific across-row and within-row leaf orientation and was compared to the conventional random seed orientation. The seed orientation that produced across row leaf orientation had 4.4 to 9.7 percent higher corn grain yields compared to random seed orientation.
Torres et al. (2017) conducted field trials by hand planting corn seed with two specific orientations (upright and flat), resulting in the desired leaf orientation and random seed orientation. The seed orientations were upright with the caryopsis pointed down and parallel to the row, and lying flat with the embryo up and perpendicular to the row. Results from the five-site yearlong study showed that seeds planted upright had a 0 to 19 percent yield increase relative to random placement. Data from Torres et al. (2017), Kaufman (2013), Toler et al. (1999), and Taylor et al. (2015) were all considered for this analysis. Additional information regarding the use of the data is available in the data section.
Kaufman (2013) studied the effect of orienting corn seed on grain and silage yield. Seeds were manually planted with the tip down and the embryo facing the row middle or aligned with the row direction. A randomly oriented treatment was planted with a mechanical seeder. Kaufman (2013) found a 14 percent increase in grain yield for hand-planted seed versus mechanically planted seed, regardless of the embryo orientation. The previous two studies (Toler et al., 1999; Torres et al., 2017) planted all treatments by hand. There was no machine-planted treatment. For comparative purposes, Kaufman (2013) found grain yield for hand-planted seed with the embryo facing the row middle was 9% greater than hand-planted seed with the embryo facing the row direction.
Hand planting is not feasible on a large scale. Large-scale implementation would require a planter capable of placing seeds in the soil with a controlled orientation. Traditionally, planting equipment and technology manufacturers have focused on more precise metering and delivery of various seed sizes (Badua et al., 2021; Li et al., 2015). While commercial devices that convey the seed from the meter to the seed trench exist, most commercial planters are still dropping the seed from about 18 inches above the seed trench. Either way, the seed is still randomly oriented once it reaches the furrow. Random seed orientation results in random leaf orientation once it emerges.
Past studies show that controlling corn seed orientation can increase corn yield. In summary, if seed orientation can be manipulated, then favorable leaf orientation can be produced, resulting in homogenous maize seedling emergence. This would allow for more homogenous corn seed stands with less interplant competition while increasing light interception. Despite data limitations, it is important to evaluate the potential financial impact of such technology. With at least a baseline financial analysis, the potential benefit to the farmer in terms of increased profit from orienting corn seed, given specific assumptions and price parameters for the technology, can be estimated.
The objective of this research is to estimate the potential value of corn seed orientation technology, using cost-benefit analyses. To meet this objective, three different machinery use levels were evaluated. Because oriented seed technology does not exist in the marketplace, three different price points based on the cost of similar technology were used in this evaluation. This research is of interest to developers and manufacturers developing such technology, as well as researchers considering further evaluation of oriented corn seed placement. Producers with long-term machine purchasing plans may also be interested in these results and may consider incorporating this technology if it becomes available in the future.
Methodology
The purpose of this study is to determine the potential benefit of oriented corn seed placement and to compare potential returns from using this technology to non-oriented corn seed planting. This study refers to traditional corn seed placement technology (TSP) as an existing planter planting corn seeds without any specific orientation method. In other words, TSP plants corn seeds randomly in the furrow/soil. Oriented corn seed placement technology (OSP) is described as a corn planter planting corn seeds in a way that will result in symmetrically oriented leaves across rows among the plant population. For instance, placing corn seed in the soil with the point of caryopsis attachment down.
Economic Model
Generally, a profit-maximizing producer will either want to reduce input costs or increase the productivity of their farm operations. This study draws on profit maximization theory to determine the planting technology alternative (TSP or OSP) that maximizes the expected net present value (NPV). In order to discount the simulated cash inflows to their present value, NPV is often the capital budgeting technique used. NPV is especially important when comparing two alternatives because it accounts for both the time value of money and the size of the stream of cash flows over the life of the investment (Kay et al., 2016).
The estimated NPV is given by using equation 1:
(1)
where
E(Rt,U,S) = expected annual net return for S
S = either TSP or OSP
U = usage level which is reflected by the number of hectares.
r = discount rate.
The discount rate accounts for the time value of money. The commonly employed 10% was used in this analysis. The equation is summed from year t to T. The number of hectares is dependent on the usage level U, which is either low, medium, or high. T is set to 5 years.
The expected (E) net return Rt,U,S per year was estimated in equation 2:
(2)
where Rt,U,S is the Revenuet,U,S generated in year t for hectares h less the Costt,U,S incurred in year t for hectares h.
Equation 3 shows the revenue per year under technology S is a function of yield (Yt,h) and corn price (PCt):
(3)
where Yt,h is the corn yield in year t for hectares h, and PCt is the price of corn in year t, which are both stochastically determined. I t,S is the increase in yield for year t given technology S. Under TSP, the increase in yield is zero and is based on the distribution of historic yields. Under OSP, a stochastically determined percentage increase in yield will be added to Yt,h. Note that the distribution of potential percentage yield increases for OSP includes 0. Therefore, there may be some years where OSP gives no advantage, and the yield will be the same for TSP and OSP. The yield per acre was drawn from the distribution and then multiplied across all acres. This results in a pseudo-average yield across the farm. The yield between acres would likely differ; however, given the wide range of distributions, the average yield approach was used. Yield assumptions are further discussed in the data section.
Table 1. Corn yield results from previous seed orientation research. Source Oriented Yield, OSP
(Mg/ha)Traditional Yield, TSP
(Mg/ha)Yield Increase Used in Analysis[a]
(%)Torres et al. (2017) 2.22 2.44 0.00 Torres et al. (2017) 2.95 2.77 6.49 Torres et al. (2017) 4.12 3.93 0.00 Torres et al. (2017) 5.24 4.87 7.46 Torres et al. (2017) 6.94 5.83 19.14 Kaufman (2013) 13.00 11.90 9.23 Kaufman (2013) 12.00 11.60 0.00 Taylor et al. (2015) 11.41 11.62 0.00 Taylor et al. (2015) 13.51 13.50 0.00 Taylor et al. (2015) 14.81 15.19 0.00 Taylor et al. (2015) 9.03 9.38 0.00 Taylor et al. (2015) 10.19 9.33 0.00 Taylor et al. (2015) 8.76 10.48 0.00 Taylor et al. (2015) 13.14 12.97 0.00 Taylor et al. (2015) 15.18 14.69 0.00 Taylor et al. (2015) 16.51 16.85 0.00 Toler et al. (1999) 8.98 8.60 4.38 Toler et al. (1999) 10.67 9.73 9.68
[a] Only statistically significant changes were included in the analysis. Values that were not statistically significant were assigned zero.
Equation 4 shows the cost per year under scenario S:
(4)
where
OCt,h = operating costs, including seed, fertilizer, chemicals, custom services, fuel, lube, electricity, repairs, purchased irrigation water, and interest on operating capital in year t for hectares h
AOt,h = allocated overhead, including hired labor, opportunity cost of unpaid labor, capital recovery of machinery and equipment, opportunity cost of land, taxes and insurance, general farm overhead, and total allocated overhead in year t for hectares h
MCt,S = cost of the oriented corn seed planter, is referred to as the technology cost, and only applies under the OSP scenario. The technology cost occurs at t=0.
The payback period is the amount of time it would take for an investment to return its cost through the cash revenue it generates (Kay et al., 2016). The payback period is not a measure of profitability but instead is a measure of how quickly the investment will contribute to liquidity (Kay et al., 2016). In equation 5, the payback period is calculated by dividing the cost of the oriented technology (high, medium, or low) by the difference between the oriented cash flow and the traditional cash flow.
(5)
Data
Data used to parameterize the model were mainly sourced from past research studies and the U.S. Department of Agriculture-Economic Research Service (USDA-ERS, 2022). Previous research on OSP was used to determine the potential yield increase from this technology (table 1). The OSP yield was compared to the yield for TSP. Where appropriate, the data in table 1 are segregated by site and seeding rate. If the yield between the two treatments was statistically different, the percentage increase was calculated. The yield increases for all other non-statistically significant comparisons were set to zero. Data from USDA-ERS (2022) primarily included the cost of inputs on a per-hectare basis, prices of corn in dollars Mg-1, and corn yield in Mg ha-1, spanning from 1996 to 2021 (26 years) and listed at the national level.
Table 2. Summary statistics for data variables.[a] Variable Minimum Mean Maximum Cost per hectare ($/ha) $1,380.85 $1,691.26 $2,055.91 Base yield per hectare (traditional planting) (Mg/ha) 7.41 9.65 11.55 Corn Price ($/Mg) $94.68 $163.43 $314.68
[a] Calculated from historical USDA data (USDA-ERS, 2022).
Yield Data
A producer using TSP is perceived to use already existing corn planter technology, which randomly drops corn seed in furrows during planting. Therefore, the distribution of yield outcomes was developed using historical yield data (table 2). The minimum yield used for the triangular distribution was 7.41 kg ha-1, the mean was 9.65 kg ha-1, and the maximum was 11.55 kg ha-1 (USDA-ERS, 2022). For a producer who chooses OSP, a percentage increase based on previous research was added to the TSP yield. To calculate the potential increased yield values for OSP, this study first calculated the percentage increase in yield between TSP and OSP from a number of previous studies (table 1). The distribution of potential outcomes was plotted and used stochastically in the Monte Carlo simulation (fig. 1). For each simulated year, a yield was drawn from the triangular distribution of yield for the TSP scenario. Next, a percentage increase was drawn from the distribution of oriented seed percentage increases and added to the original yield. Note that the percentage increase in yield for the oriented seed technology could be zero. For example, with the given distribution, the simulated percentage increase in yield was between 0 and 1, or 46 percent of the time. The price, yield, and costs were uncorrelated within our simulation.
Production Cost and Corn Sale Price
The USDA-ERS reports an enterprise budget for corn production, including all costs and returns per-planted-acre, at the national level (USDA-ERS, 2022). Operating costs included: seed, fertilizer, chemicals, custom services, fuel, lube, electricity, repairs, purchased irrigation water, and interest on operating capital. Allocated overhead included: hired labor, opportunity cost of unpaid labor, capital recovery of machinery and equipment, opportunity cost of land, taxes and insurance, general farm overhead, and total allocated overhead. The total costs were summed and then adjusted for inflation. In total, per hectare, the minimum cost used in the triangular distribution was $1381, the mean was $1691, and the maximum was $2056 (table 2). Historic corn sale prices were also taken from UDSA-ERS (2022) and adjusted for inflation. For the triangular distribution of corn price per Mg, a minimum price of $95, a mean price of $163, and a maximum price of $315 was used. Although current 2022 input costs are likely high, it is important to consider the overall fluctuation in prices occurring over time. Therefore, using inflation-adjusted historical data allowed us to simulate natural fluctuations in prices, presenting a wider range of potential outcomes and better representing a longer-term investment.
Figure 1. Corn yield discrete probability distribution. Cost of the Planter and Technology
The cost of the planter was captured in the USDA capital recovery of machinery and equipment. Therefore, for the TSP, there was no additional cost. An add-on cost for the oriented corn seed placement technology was assumed at $32,000, $96,000, or $160,000. These additional costs are based on $2,000, $6,000, and $10,000 per row for the technology on a 16-row planter. This range is similar to the currently available technology for controlled seed delivery in high-speed planters. While this is a wide range in costs, we believe a mechanism could be developed and sold within this range. For example, a mechanism that could be coupled with an existing metering device would likely cost less than a mechanism that required a completely new metering system.
Sensitivity Analysis
One limitation of this research is that the technology analyzed does not currently exist in the marketplace. Due to the experimental nature of this analysis, sensitivity analysis was conducted to encompass varying degrees of machine usage, and machine pricing. Sensitivity analysis allows us to model a variety of potential outcomes, while using the limited data currently available. The data used for sensitivity analysis are shown in table 3, with an explanation following the table.
Table 3. Variables and values used for sensitivity analysis in the simulation. Sensitivity Analysis Low Medium High Producer usage assumptions Total farm acreage, ha 647 971 1295 Corn acreage, ha 324 486 647 Time period analyzed 5 5 5 Machine cost assumptions Cost of machine $32,000 $96,000 $160,000 Corn Planter Usage Analysis
This analysis is based on a 16-row planter with 76 cm of row spacing. Three levels of corn planter usage (low, medium, and high-use) were used in the analysis. The use levels were based on the planter covering 40.5, 60.7, and 80.9 hectares per year per row. Thus, three farm sizes were considered in this analysis: small/low-use (647 ha), medium/medium-use (971 ha), and large/high-use (1295 ha). It was assumed that the producer would plant corn on 50% of the land annually. Since this analysis focuses on comparing two different corn planting technologies, the revenue and costs from other crops are not considered.
The time period analyzed was set to five years, regardless of annual use. While this will not represent the wear on the device, it more accurately represents the technological obsolescence of the device. This also allows comparison of results across producer usage levels, since the lifespan is the same. In reality, spreading machine usage over a greater area decreases the per-ha cost, but may result in additional repair and maintenance costs, but these calculations are beyond this hypothetical analysis.
Results and Discussion
Based on the varying degrees of machine usage and machine pricing, 12 different NPV results were generated for comparison. Three net present values were computed for TSP based on the three corn planter usage types (low, medium, and high-use). For OSP, each planter usage type was also evaluated under the three technology cost possibilities (table 4).
Table 4. Net present values of Oriented Placement (OSP) and Traditional Placement (TSP). NPV[a] Low-use Producer Medium-use Producer High-use Producer Traditional Corn Seed Placement Minimum -$1,843,622 -$1,270,566 -$1,551,874 Mean $142,531 $213,872 $285,126 Maximum $1,397,852 $2,314,055 $2,786,775 Probability of a positive NPV 69% 69% 69% Oriented Corn Seed Placement Technology cost
$32,000Minimum -$834,781 -$1,126,355 -$1,636,635 Mean $140,715 $225,823 $310,848 Maximum $1,193,228 $1,805,813 $2,547,863 Probability of a positive NPV 70% 72% 72% Average Payback Period 2.73 1.82 1.37 Technology cost
$96,000Minimum -$860,505 -$1,198,092 -$1,497,618 Mean $82,575 $167,485 $252,496 Maximum $1,212,192 $2,064,213 $2,834,016 Probability of a positive NPV 62% 66% 68% Average Payback Period 8.20 5.47 4.12 Technology Cost
$160,000Minimum -$858,555 -$1,176,544 -$1,585,641 Mean $24,459 $109,340 $194,443 Maximum $1,203,690 $2,014,849 $2,477,257 Probability of a positive NPV 53% 60% 64% Average Payback Period 13.66 9.12 6.86
[a] For all NPV calculations, a discount rate of 10% was used.
For a low-use producer using the traditional corn seed placement technology, the NPV minimum was -$1,843,622, the mean was $142,531, and the maximum was $1,397,852 (table 4). The value of the NPV represents the return, accounting for the time value of money, for a 5-year period of planting corn on 324 hectares using traditional planting methods. The probability of a positive NPV suggests the rate at which the discounted stream of revenues will exceed the discounted stream of costs. As expected, when comparing the OSP scenarios, as the technology cost increased, the NPV decreased. For the low-cost technology ($32,000) and low-use producer, the mean NPV was $140,715. For the medium-cost technology and low-use producer, the mean NPV was $82,575, and the maximum-cost technology had a mean NPV of $24,459. A higher net present value indicates the scenario, for example, using oriented corn seed technology, will provide a higher economic return and should be chosen. For the low-use producer, under the technology costs evaluated, the OSP should be potentially chosen only in the scenario where the machine costs $32,000. The mean NPV is slightly lower, but the probability of having a positive NPV is slightly higher, so risk preferences would need to be considered. Even for TSP, under all scenarios, the probability of having a positive NPV was only 69%. It is important to remember that insurance or government disaster payments were not included in this analysis. Most farmers would protect themselves from the negative implications of a poor yield through several measures. When considering the low-cost technology under OSP, the probability of a positive NPV was higher than that under TSP. The probability of a positive NPV was only 53% under the low-use, high-cost machine scenario. The payback period under that scenario was almost 14 years, which is much higher than the 2.73-year payback period for the low-cost/low-use scenario.
Similarly, over a 5-year life cycle, a medium-use producer using TSP has a minimum NPV of -$1,270,566, a mean of $213,872, and a maximum of $2,314,055 (table 4). The probability of a positive NPV was 69%. Only the low-cost technology under the OSP scenario had a higher probability of a positive NPV when compared to TSP. Under the “best” of the OSP scenarios (lowest machine cost), the probability of a positive NPV was only 3% higher. Under the high technology cost scenario, the oriented corn seed placement had a lower NPV than TSP, with a minimum of $1,176,544, a mean of $109,340, and a maximum of $2,014,849.
The high-use producer, over a 5-year lifecycle and 647 hectares, had a similar percentage increase in positive NPV when comparing TSP and the low-cost technology under OSP (table 4). The probability of a positive NPV for the high-use producer using TSP was 69%. For a high-use producer using OSP under the low technology cost scenario, the probability of a positive NPV was 72%. Again, as expected, the NPV decreased for OSP scenarios as the technology cost increased. The high-use producer had the fastest payback periods, which is expected considering they are spreading the cost of the machine over more acres. The fastest payback period was 1.37 years for the high-use producer under the low technology cost scenario. The medium technology cost resulted in NPV’s and probability of positive NPV that were marginally worse than TSP. The mean NPV was $252,496 and the probability of a positive NPV was 68%. Small improvements in yield over the distribution used in this research, or a small decrease in the price of the machine could result in OSP being a better choice than TSP in this scenario.
Overall, OSP technology has higher simulated NPV values when compared to traditional corn seed placement technology only if the machine is at a lower cost and the usage is high. A critical look at the worst-case scenarios shows the minimum NPV’s for OSP for most of the scenarios are relatively better when compared to TSP. When TSP has higher negative NPV values than OSP, some yield risk has been mitigated.
Although the increase in yield from oriented seed placement can be zero, it should never be negative. In other words, with all other seed placement parameters (depth, spacing, and seed/soil contact) equal, the oriented seed placement will always do as well as the traditional (random) placement method. Therefore, these results are not surprising. As long as the benefit from the increased yield exceeds the price point of the OSP technology, OSP will result in a higher NPV. Knowing the true cost of the OSP technology will be the deciding factor regarding the potential increase in profitability for farmers. There may be additional analysis needed for the high-use producer, as they may incur more maintenance and repair costs, since they are using the machine over more acres. However, the payback period for the high-use producer under the lowest machine cost was still only 1.37 years.
The field research conducted on OSP was all done by hand. Until machine trials are completed, these estimated yield increases are the best available data to be used for these types of analyses. Until further research is conducted, it is unclear if the oriented placement machine, which is necessary to scale up, will result in the same increased yields as the hand-placed seed. Twelve out of the 18 yield observations showed a 0% increase in yield using the OSP technology. Understanding under what conditions the oriented yield increase was zero could be evaluated in future field trials and would improve the analysis. Further analysis will benefit from more data regarding potential yield increases and more data regarding the true cost of purchasing the technology.
Conclusion
Gains in yield stem largely from scientific advances in areas like genetics, fertilizers, and equipment. OSP presents another opportunity to increase yields. Past research has shown that controlled seed orientation at planting leads to symmetrically oriented leaves across rows, resulting in increased grain yields. Although currently in its infancy, a preliminary analysis of the potential financial gains of oriented corn seed technology is important when justifying additional research, the manufacturing of prototypes, and discussing new advances with farmers.
This study simulated the potential value of OSP technology using potential yield increases from the literature, historic corn production costs, and sale prices. Three different corn planter use levels and three different oriented corn seed technology price points are the focus of this evaluation. Using stochastic analysis, NPV differences were compared with and without the new corn planter technology.
When considering the two different technologies of OSP and TSP, both generate positive mean net present values under all corn planter usage levels. However, OSP (under the technology costs evaluated) generates a higher mean NPV and higher probabilities of positive NPV only under low-cost technology scenarios.
More research is needed to confirm or adjust current yield estimates from oriented corn seed technology. Accurate yield estimates, as well as accurate cost estimates are necessary for farmers to make any decision regarding adoption. As long as the additional revenue from increased yield outweighs the cost of technology adoption, OSP technology will be of interest to farmers. Additional research is needed to assess how OSP technology will fit in with different crop mixes. In this analysis, it was assumed that corn would be planted on the hectares included for analysis. A whole farm analysis would more accurately project financial benefits.
Acknowledgments
This research was supported by CNH Industrial and the Oklahoma Agricultural Experiment Station.
References
Badua, S. A., Sharda, A., Strasser, R., & Ciampitti, I. (2021). Ground speed and planter downforce influence on corn seed spacing and depth. Precis. Agric., 22(4), 1154-1170. https://doi.org/10.1007/s11119-020-09775-7
Drouet, J. L., & Moulia, B. (1997). Spatial re-orientation of maize leaves affected by initial plant orientation and density. Agric. For. Meteorol., 88(1), 85-100. https://doi.org/10.1016/S0168-1923(97)00047-6
Fortin, M.-C., & Pierce, F. J. (1996). Leaf azimuth in strip-intercropped corn. Agron. J., 88(1), 6-9. https://doi.org/10.2134/agronj1996.00021962008800010002x
Kaufman, T. D. (2013). The effects of planting techniques on maize grain yield and silage production. MS thesis. Illinois State University, Department of Agriculture.
Kay, R., Edwards, W. M., & Duffy, P. A. (2016). Farm management (8th ed.). New York: McGraw Hill.
Li, Y., Xiantao, H., Tao, C., Dongxing, Z., Song, S., Zhang, R., & Mantao, W. (2015). Development of mechatronic driving system for seed meters equipped on conventional precision corn planter. Int. J. Agric. Biol., 8(4), 1-9. https://doi.org/10.3965/j.ijabe.20150804.1717
Taylor, R. K., Koller, A. A., Yazgi, A., Ciampitti, I., Schlegel, A., Godsey, C., & Navid, H. (2015). Evaluation of corn seed orientation. Paper No. 15-2134331. Proc. 2015 ASABE Annual Int. Meeting. St. Joseph, MI: ASABE. https://doi.org/10.13031/aim.20152134331
The Economist. (2022). Climate change will force farmers to reshuffle what is grown where time to develop a taste for breadfruit. Retrieved from https://www.economist.com/graphic-detail/2022/11/10/climate-change-will-force-farmers-to-reshuffle-what-is-grown-where
Toler, J. E., Murdock, E. C., Stapleton, G. S., & Wallace, S. U. (1999). Corn leaf orientation effects on light interception, intraspecific competition, and grain yields. J. Prod. Agric., 12(3), 396-399. https://doi.org/10.2134/jpa1999.0396
Torres, G. M., Koller, A., Taylor, R., & Raun, W. R. (2017). Seed-oriented planting improves light interception, radiation use efficiency and grain yield of maize (Zea mays L.). Exp. Agric., 53(2), 210-225. https://doi.org/10.1017/S0014479716000326
Torres, G., Vossenkemper, J., Raun, W., & Taylor, R. (2011). Maize (Zea mays) leaf angle and emergence as affected by seed orientation at planting. Exp. Agric., 47(4), 579-592. https://doi.org/10.1017/S001447971100038X
USDA. (2022). A look at agricultural productivity growth in the United States, 1948-2017. Retrieved from https://www.usda.gov/media/blog/2020/03/05/look-agricultural-productivity-growth-united-states-1948-2017
USDA-ERS. (2022). Commodity costs and returns. Retrieved from https://www.ers.usda.gov/data-products/commodity-costs-and-returns/