Environmental Factors Associated With Nitrogen Fixation Prediction in Soybean.

Area of Science:

• Agricultural Science
• Plant Physiology
• Soil Science

Background:

• Biological nitrogen (N)-fixation is the primary N source for soybean (Glycine max), vital for sustainable intensification.
• Understanding environmental drivers of N-fixation is key to optimizing soybean productivity and seed protein.

Purpose of the Study:

• To identify key environmental factors influencing soybean N-fixation.
• To develop predictive models for N-fixation, yield, and seed protein concentration.
• To assess the role of N-fixation in soybean productivity under varying environmental conditions.

Main Methods:

• Analyzed 40 environmental factors (weather, soil, crop management) using elastic net regularization of multiple linear regression.
• Used relative abundance of ureides (RAU) as an indicator for the fraction of N derived from N-fixation.
• Developed predictive models for RAU, yield, and seed protein, validated via cross-validation.

Main Results:

• Soybean N-fixation ranged from 60-98%, with key predictors including N fertilization, vapor pressure deficit (VPD), precipitation, sowing date, drought stress, soil CEC, and sulfate concentration.
• The RAU predictive model achieved an R-squared of 0.69 with a relative mean square error of 4.5%.
• VPD during early reproductive stages significantly impacted RAU, yield, and seed protein.

Conclusions:

• Environmental factors critically regulate soybean N-fixation, offering targets for improved crop management.
• Predictive models integrating environmental data enhance understanding of N-fixation's contribution to soybean yield and protein.
• This research provides a foundation for sustainable intensification of soybean production through optimized N-fixation management.