Dynamics of canopy closure, yield, and quality under heterogeneous plant spacing in sunflower (Helianthus annuus L.)

Authors: OLSON, NEIL - North Dakota State University; TROSTLE, CALVIN - Texas A&M University; MEYER, RONALD - Colorado State University; Hulke, Brent

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sunflower yields in producer fields can be limited by plant population density in the field; however, what level of reduction in plant population density or changes in distribution of plants causes yield loss is poorly understood. This experiment looked at the introduction of large gaps in properly spaced sunflower populations, as well as changes in distribution of plants (increasing what are called skips and doubles), compared to a properly spaced control treatment, to understand how plant distribution affects yield and quality of the seeds. Additionally, we observed the effects of these treatments on canopy closure and demonstrated a new method of doing so with drone-based imagery. The results showed that considerable departure from proper spacing was required to result in yield loss in all three of the Great Plains locations studied, suggesting that sunflower was very resilient to improper plant spacing and could easily compensate for it; however, plants lost to disease did increase in some treatments. This provides needed information to producers that can guide replant decision-making in cases where plant population disturbance is a concern.

Technical Abstract: The objective of this study was to evaluate the effects of plant population heterogeneity on yield, quality, and canopy closure in confectionery and oilseed sunflowers. Field experiments were conducted in Minnesota, Texas, and Colorado, revealing that yield was occasionally influenced by heterogeneity, with more uniform stands yielding higher. Confectionery sunflowers compensated for yield losses by producing larger seeds, while oilseed sunflowers increased seed production per head. Unharvested plants were more prevalent in less uniform stands, and faster canopy closure was achieved in uniformly spaced plants. These findings underscore the importance of uniform plant spacing for effective weed suppression and crop performance. Irregular plant stand heterogeneity may exacerbate yield loss due to site-specific stresses. The study provides valuable insights for optimizing sunflower production and highlights the need for further research into sunflower yield compensation mechanisms.