October 7, 2009
Corn plants can break yield barrier with right resources, study shows
WEST LAFAYETTE, Ind. - |
"The only way to pursue and achieve higher grain yields on a per-acre basis at high plant densities is to make sure that every single plant has the opportunity to compete with its neighbor in the row," said agronomy professor Tony Vyn. "The only way to achieve this competition ability is to have the genetic resources, in terms of a hybrid's ability to compete and gain access to nutrients and water."
The results of this three-year study, which looked at approximately 4,000 individual plants each of the three years, are published in the early online version of Agronomy Journal. A downloadable version of the article is available at https://www.agronomy.org/publications/agronomy-journal/view/101-6/aj09-0082-pub.pdf
Each year from the time that seedlings first emerged from the soil, the plants were barcoded. Vyn's team grew to understand how individual plants compete with neighbors at three different plant densities and three different nitrogen rates.
"This study is perhaps the most comprehensive study that's ever been done to look at the multiple stress effects on individual corn plant performance during its growth stages, as well as on the final result in terms of grain yield per plant," Vyn said.
One misconception the industry has is that barren plants or ears with only a few kernels at the end of the growing season are a result of when the plant first emerged from the soil back in the very beginning, Vyn said.
"It actually has a lot more to do with how that plant was able to compete with its neighbor in terms of capturing sunlight, producing a big leaf area, trying to silk and have the pollen shed at the same time, and retain green leaves well into the grain-fill period," he said. "Essentially, there is a seasonlong, but management-dependent, intense competition that occurs among adjacent plants.
"Competition is enhanced at high plant densities, especially when nitrogen is limiting. So nitrogen is an example of a nutrient that becomes more essential at high plant densities in order to avoid the keen establishment of hierarchies where there are many dominated plants and then a few very dominant plants, which have the ability to marshal more resources into their growth so that they have a high yield."
Vyn found that the anthesis-to-silking interval is crucial to the final grain yield.
"Basically, if you have plants that have been dominated by their neighbors, they will tend to shed pollen on time, but they will have a very delayed emergence of the silk," he said. "So the main reason for barrenness in corn plants has to do with the long time interval between pollen shed on the tassel and silk development of the ear."
From an industry standpoint, Vyn said that as the future of corn yield improvement is considered, seed companies must study the response of their hybrids and germplasms to higher plant densities in the context of nitrogen use efficiency.
"As we've tried to push yield barriers beyond 300 and 350 bushels per acre, it's extremely important that we think about the ability of the plant to tolerate not just a single stress like high plant density, but also be able to tolerate lower nitrogen availability on a per-plant basis," Vyn said. "Our results suggest that on the plant breeding side of the equation, more attention should be focused on the joint ability of new corn hybrids to tolerate combined stresses of both high plant density and limited nitrogen.
"If the new hybrids can better tolerate both, then it will be possible for those high-density, low-nitrogen situations to achieve an overall improvement in uniformity of grain yield on a per-plant basis."
Funding for this research was provided by the Purdue Research Foundation, a Pioneer Fellowship in Plant Sciences and a Purdue University Andrews Foundation Fellowship. Pioneer Hi-Bred International Inc. provided seed and Deere & Co. loaned field and automatic guidance equipment.
Writer: Julie Douglas, 765-496-1050, douglajk@purdue.edu
Source: Tony Vyn, 765-496-3757, tvyn@purdue.edu
Ag Communications: (765) 494-8415;
Steve Leer, sleer@purdue.edu
Agriculture News Page
PHOTO CAPTION:
Chris Boomsma, a doctoral student and lead author, measures the heights of adjacent corn plants in the V-5 stage with variable growth and known emergence dates in late May 2005. (Purdue University photo)
A publication-quality photo is available at https://www.purdue.edu/uns/images/+2009/vyn-cornresearch.jpg
Maize Morphophysiological Responses to Intense Crowding and Low Nitrogen Availability: An Analysis and Review
Christopher R. Boomsma, Judith B. Santini, Matthijs Tollenaar, and Tony J. Vyn
Mounting concerns over the cost and environmental impact of N fertilizer combined with progressively higher plant densities in maize (Zea mays L.) production systems make progress in maize N use efficiency (NUE) and N stress tolerance essential. The primary objectives of this 3-yr field study were to (i) evaluate the N responsiveness, NUE, and N stress tolerance of multiple modern maize genotypes using suboptimal, optimal, and supraoptimal plant densities (54,000, 79,000, and 104,000 plants ha–1, respectively) with three levels of side-dress N (0, 165, and 330 kg N ha–1), (ii) identify key morphophysiological responses to the simultaneous stresses of intense crowding and low N availability, and (iii) consider our results with extensive reference to literature on maize morphophysiological responses to plant crowding and N availability. At optimal and supraoptimal plant densities, maize receiving 165 kg ha–1 of side-dress N displayed strong N responsiveness, high NUE, pronounced crowding tolerance, and plant density independence. However, crowding tolerance was contingent on N application. Relative to less crowded, N-fertilized environments, the 104,000 plants ha–1, 0 kg N ha–1 treatment combination exhibited (i) reduced pre- and postanthesis plant height (PHT), stem diameter (SD), and total biomass; (ii) greater preflowering leaf senescence and lower R1 leaf areas at individual-leaf, per-plant, and canopy levels; (iii) enhanced floral protandry; (iv) lower pre- and postanthesis leaf-chlorophyll content; (v) lower per-plant kernel number (KN P), individual kernel weight (KW), grain yield per plant (GYP), and harvest index per plant (HI P); and (vi) enhanced per-plant grain yield variability (GYCV). Genetic efforts to improve high plant density tolerance should, therefore, simultaneously focus on enhancing NUE and N stress tolerance.
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