Soybean plants growing in rows with glowing roots.

The Secrets of Soybean Success: How Sowing Dates Impact Your Yield

Rhea Morgan in Climate & Environment December 2025 • 4 min read.

"Unlock the full potential of your soybean crop by mastering the art of timing. Discover how sowing dates affect plant development and maximize your harvest."

A plant’s phenological study offers invaluable insights, enabling us to pinpoint quantitative changes at specific growth stages. By addressing the varying necessities of plants, we pave the way for optimal crop development and, ultimately, bountiful yields. The timing of agricultural practices significantly impacts the well-being of crops.

Soybean (Glycine max) stands out as a crop profoundly influenced by the interaction between its genotype and the surrounding environment. Its cycle and vegetative development undergo transformations shaped by this dynamic interplay. Temperature and photoperiod emerge as pivotal factors orchestrating variations in the crop's growth trajectory.

Recognizing the importance of understanding these interactions, a study was conducted to analyze the phenological and quantitative plant development changes in soybean cultivars caused by sowing date and their relation to yield. By unraveling these dynamics, we aim to empower farmers with the knowledge to optimize their sowing strategies and unlock the full potential of their soybean crops.

Decoding Soybean Development: The Impact of Sowing Dates

Soybean plants growing in rows with glowing roots.

The study, conducted in Guarapuava, Parana State, Brazil, focused on four soybean cultivars (FPS Urano®, BMX Apolo® RR, BMX Energia® RR and BRS 284®) with contrasting growth habits. These cultivars were planted on three different sowing dates: October 21, November 18, and December 20, 2010. Throughout the growing season, researchers meticulously monitored various plant characteristics at key growth stages (V4, V9, R2, and R5.3).

Plant height, stem diameter, node count, branch number, and leaf area index (LAI) were measured to capture the quantitative changes. Additionally, the number and dry matter (DM) of nodules were assessed at the R5.3 growth stage to evaluate the impact of sowing date on nitrogen fixation. The study sought to determine how different sowing dates affected these key parameters and ultimately influenced grain yield.

Delayed sowing leads to reduced growth: All cultivars exhibited reduced growth when sowing was delayed.
Determinate growth shows less response: The cultivar with a determinate growth habit was less responsive to different sowing dates compared to the others.
Nodule DM increases with October sowing: The dry matter of nodules was higher when plants were sown in October.
Larger LAI increases nodule DM: Cultivars with larger leaf area index (LAI) obtained more dry matter of nodules.
Plant characteristics defined post-V9: The final quantitative characteristics of the plants were determined after the V9 growth stage.
LAI correlates with yield: Leaf area index at R5.3 showed the highest correlation with grain yield.

The study revealed a clear trend: delaying sowing dates led to a reduction in growth across all soybean cultivars. However, the cultivar with a determined growth habit exhibited less sensitivity to these variations. This finding suggests that certain cultivars may be better suited for late-season planting scenarios. Furthermore, the study highlighted the importance of sowing date for nodulation. Plants sown in October exhibited higher nodule dry matter, indicating enhanced nitrogen fixation. Interestingly, cultivars with larger leaf area index (LAI) also tended to have more nodule dry matter, suggesting a link between photosynthetic capacity and nitrogen fixation.

Optimizing Soybean Yield: The Key Takeaway

In southern Brazil, delaying sowing reduces the quantitative plant characteristics and phenological development of all soybean cultivars studied, independently of growth habit. If nodulation is a parameter, dry matter, rather than number, should be observed more attentively when selecting soybean cultivars with high yield potential in breeding programs.

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This article is based on research published under:

DOI-LINK: 10.5897/ajar2014.9325, Alternate LINK

Title: Phenological And Quantitative Plant Development Changes In Soybean Cultivars Caused By Sowing Date And Their Relation To Yield

Subject: General Agricultural and Biological Sciences

Journal: African Journal of Agricultural Research

Publisher: Academic Journals

Authors: Pierozan Junior Clovis, Kawakami Jackson, Bridi Marcelo, Viotto Del Conte Murilo, Michalovicz Leandro

Published: 2015-02-05

Everything You Need To Know

How do different sowing dates influence the growth of different soybean cultivars?

The research, conducted in Guarapuava, Parana State, Brazil, showed that delaying sowing dates led to reduced growth across all studied soybean cultivars, including FPS Urano® , BMX Apolo® RR, BMX Energia® RR, and BRS 284®. However, the cultivar with a determinate growth habit demonstrated less sensitivity to these variations compared to others. This suggests that the best sowing date may depend on the specific cultivar being used and its growth characteristics.

Why is the Leaf Area Index (LAI) so important in soybean yield, and how does sowing date affect it?

The Leaf Area Index (LAI) at the R5.3 stage showed the highest correlation with grain yield in the study. LAI reflects the plant's photosynthetic capacity. The study revealed that cultivars with a larger LAI tended to have more nodule dry matter, indicating a link between photosynthetic capacity and nitrogen fixation. The sowing date impacts LAI; delaying sowing generally reduces plant growth, affecting the eventual LAI and, consequently, the potential grain yield.

What were the specific soybean cultivars studied, and what were the sowing dates evaluated?

The study focused on four soybean cultivars: FPS Urano®, BMX Apolo® RR, BMX Energia® RR, and BRS 284®. These were planted on three different sowing dates: October 21, November 18, and December 20, 2010. The researchers monitored plant characteristics at key growth stages (V4, V9, R2, and R5.3) to assess the impact of these sowing dates on the cultivars' development and yield.

How does sowing date affect nodulation and nitrogen fixation in soybeans?

The study showed that the dry matter of nodules was higher when plants were sown in October. This indicates that early sowing dates can enhance nitrogen fixation. Cultivars with a larger Leaf Area Index (LAI) also tended to have more nodule dry matter, suggesting a connection between photosynthetic capacity and nitrogen fixation. The timing of sowing significantly impacts the plant's ability to efficiently fix nitrogen from the atmosphere.

What are the implications of the study's findings for soybean farmers in southern Brazil?

The study's findings suggest that in southern Brazil, farmers should prioritize early sowing to maximize soybean yield potential. Delaying sowing reduces plant growth and development across all cultivars. Farmers need to consider the specific growth habit of their chosen cultivars, as those with determinate growth habits may be less affected by later sowing dates. Additionally, the study highlights the importance of monitoring nodulation and selecting cultivars with high nitrogen fixation capabilities, particularly by observing dry matter rather than the number of nodules.