Project Details:

Investigation of the causes of low nutrient concentrations in high-yielding soybean cultivars

Parent Project: This is the first year of this project.
Checkoff Organization:Alabama Soybean Producers
Categories:Breeding & genetics
Organization Project Code:
Project Year:2019
Lead Principal Investigator:Alvaro Sanz-Saez (Auburn University)
Co-Principal Investigators:
Dennis Delaney (Auburn University)
Audrey Gamble (Auburn University)
Jenn Koebernick (Auburn University)
Felix Fritschi (University of Missouri)
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Project Summary

Globally, soybean is the largest source of both animal protein and vegetable oil that provides a variety of nutrients (N, P, K) and essential elements (Fe, Zn, etc.) that are very important for animal and human nutrition. A recent meta-analysis study has demonstrated that newer, high-yielding soybean cultivars, show decrease of 18 and 13% in seed P and K concentrations compared to older soybean cultivars, respectively (Balboa et al., 2018). In addition, wheat and soybean studies have observed that although newer cultivars always show higher yield, the micronutrient concentration (Fe, Zn) in the grains is significantly decreased (Garvin et al., 2006; Fritschi, personal communication). A decrease in mineral nutrient (N, P, K) and essential element concentrations (Fe, Zn, etc.) can reduce animal and human nutrition capacity of soybean (Myers et al., 2014). The causes underlying lower nutrient concentrations in high-yielding soybean cultivars are still unknown. It is hypothesized that the increased biomass accumulation and conversion to seed in the high yielding cultivars might dilute seed nutrients like P, K, Fe, and Zn. In addition, it is also hypothesized that the nutrient uptake and transport to the shoots may be mediated by the strength of the transpiration stream that pulls the nutrients from the soil to the leaves and seeds; therefore, cultivars that display lower transpiration may results in a lower nutrient content in the seed. Another possibility is that newer soybean cultivars need higher soil nutrient availability to maintain high seed nutrient content than is needed to maximize yield.

Project Objectives

The objectives of this study are (1) to confirm in an experimental setting that newer cultivars have lower seed nutrient concentrations than older cultivars, (2) test if P and K application above the extension recommendations can increase yield and seed nutrient concentration, and (3) to test if cultivars with different transpiration capacity produce seeds with different nutrient concentration; If the above hypothesis are demonstrated to be correct, we can build on these findings in future studies in a multi-location effort comprising macro- and micro-nutrient application experiments to test if soybean seed nutrient concentrations can be maintain in high-yielding modern soybean cultivars.

Experimental Methods: to test objective 1 and 2, we will grow 3 new and 3 obsolete soybean cultivars with contrasting yield and mineral concentration, and soybean lines derived from a cross between a cultivar with high transpiration and a another one with low transpiration. We will plant 2 recombinant inbred lines (RIL) selected for high transpiration and 2 RIL selected for low transpiration capacity at EV-Smith research experimental station at Shorter, Alabama. To test objective 2, the experimental plots will be grown in control mineral nutrition following the Auburn University Extension recommendations (control), and adding +P, +K, and +P-K (60 lb above the recommendation of each nutrient). Each cultivar will be planted in a 4 row, 20 feet long plots with 4 replications forming a complete randomized block design. In order to test objective 3, two obsolete, two new, and two contrasting transpiration cultivars (chosen from the above selection depending seed availability) will be grown in a 4 row, 20 feet long plots, replicated 4 times and grown in control nutrient conditions. To test how limited transpiration affect nutrient filling in the seed, these plots will be treated with anti-transpiration sprayer (ABA) from flowering (R2) to the end of pod filling (R6) in order to reduce plant transpiration. To ensure that ABA is reducing plants transpiration stomatal conductance measurements will be taken with a leaf porometer. The control treatment for this experiment will be the nutritional control for the experiment testing objective 1 and 2.

Project Deliverables

Progress of Work

Final Project Results

Benefit to Soybean Farmers

This project will increase our understanding of the factors that are important to maintain a high nutritional value of soybean seeds with respect to mineral composition. If differences in seed mineral concentrations are observed due to the different transpiration or yield responses, we will plan further experiments in multiple locations to study if the addition of fertilizers containing micronutrients can increase mineral concentrations in the seeds; with the final goal of improving soybean production and quality.

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