Location: Soybean and Nitrogen Fixation Research
Project Number: 6070-21220-070-072-A
Project Type: Cooperative Agreement
Start Date: Oct 1, 2024
End Date: Sep 30, 2025
Objective:
Clarify the characteristics of growth and yield performance of intermediate super-nodulating and super-nodulating breeding lines in comparison to commercial checks.
Approach:
In 2025, greenhouse experiments will be repeated from 2024. Soybean lines varying in salt tolerance and nodulation capacity will be grown under greenhouse conditions in plastic columns constructed of PVC pipes (6" diameter, 39" length). The medium will be calcined, non-swelling illite and silica clay, and allows easy separation of roots. Three seeds will be sown in each column, and thinned to one at 7 days after emergence. Plants will be grown at varying N levels. At this stage, the top of each column will be covered with aluminum foil to prevent evaporation. A small slit will be made in the aluminum foil to allow the plant to grow through. Plant physiological performance will be quantified based on chlorophyll fluorescence, chlorophyll index, and leaf temperature. Plants will be harvested at maturity. The seeds will be used to estimate oil and protein content by NIR spectrometry. All columns will be weighed at the beginning (at emergence) and end of the experiment (at harvest) and also before and after any water application to estimate plant water use. At harvest, roots will be separated from shoots, and scanned using a photo scanner. Images of scanned roots will be analyzed to estimate various root traits such as root length (sum of the lengths of all roots in a root system), surface area, volume, diameter, and fine root traits. Shoots will be dried to constant weight for determining dry weight. Water use efficiency will be estimated as the ratio between biomass (shoot+root) and water use. Nitrogen content in the foliage will be estimated by isotope analysis to determine N use efficiency. The experiment will be conducted using a randomized complete block design with 4 replications.
