By Blake Jackson
At first glance, it seems logical that bigger soybean plants should deliver higher yields, but the relationship is more complex than it appears. According to Dennis Egli, UK Professor Emeritus, plant size alone does not determine productivity-it depends on how that size is achieved.
Soybean plants that grow quickly under ideal conditions-adequate moisture, proper nutrition, and minimal pressure from weeds, insects, or diseases tend to be larger and more productive.
Rapid growth, especially between growth stages R1 and R5, is critical because this is when the plant develops pods and seeds. A strong growth rate during this period often leads to higher yields, provided the crop is not stressed during seed filling (R5 to R7).
Conversely, stress during early growth or the R1 to R5 stages can slow development, resulting in smaller plants with fewer pods and reduced yield potential.
However, plant size alone does not tell the full story. Soybeans can also become large simply by growing over a longer period. For example, later-maturing varieties have an extended vegetative phase, allowing them to grow bigger even if their growth rate is similar to earlier varieties.
Research has shown that while these plants may be larger, their yields do not necessarily increase, since size is driven by time rather than growth intensity.
Planting date also influences plant size. Delayed planting shortens the growing period, leading to smaller plants. Still, smaller plants can perform well if they achieve sufficient canopy coverage to capture sunlight efficiently.
Maximizing sunlight interception is essential for photosynthesis and overall productivity, and narrower row spacing can help achieve this even with smaller plants.
Ultimately, large soybean plants can support high yields when size results from rapid growth. But when size is due to extended growth duration, it does not automatically translate into greater productivity.
Photo Credit: gettyimages-gilaxia
Categories: Kentucky, Crops, Soybeans