Yield, nitrogen, and water-use efficiency of grain sorghum with diverse crown root angle

Authors: REYES-CABRERA, JOEL - TEXAS A&M UNIVERSITY; Adams, Curtis; NIELSEN, JACKSON - TEXAS A&M UNIVERSITY; ERICKSON, J - UNIVERSITY OF FLORIDA

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2023
Publication Date: 3/3/2023
Citation: Reyes-Cabrera, J., Adams, C.B., Nielsen, J., Erickson, J. 2023. Yield, nitrogen, and water-use efficiency of grain sorghum with diverse crown root angle. Field Crops Research. 294. Article 108878. https://doi.org/10.1016/j.fcr.2023.108878.
DOI: https://doi.org/10.1016/j.fcr.2023.108878

Interpretive Summary: Grain sorghum germplasm naturally differs in crown root angle, which has been associated with different rooting patterns or “root system architectures” in the field. The root system of sorghum can be oriented in a more horizontal/shallow pattern, a more vertical/deep pattern, and in intermediate architectures. We hypothesized that different rooting architectures would perform differently in field conditions, affecting yield, nitrogen uptake, and water-use efficiency. Little testing has been done on this topic in sorghum or on agronomic crops generally. Therefore, we selected grain sorghum genotypes previously classified to exhibit ‘shallow’ (' 40.5) and ‘steep’ (' 59.3) rooting architectures to evaluate their performance under different agronomic practices, including different nitrogen fertilizer and irrigation rates. Increasing the nitrogen application rate increased crop production, but rooting architecture had minimal or no impact on crop nitrogen uptake and other parameters. There were no yield benefits or penalties associated with different rooting architectures. In testing different irrigation rates, root system architecture influenced a variety of soil response variables, including water drainage and NO3-N leaching below the rootzone, but the trends across rooting treatments and years made the results largely inconclusive. Few studies have been conducted on this topic, some showing positive outcomes, but results of these studies showed limited benefit of diverse and contrasting rooting architectures to sorghum productivity, nitrogen recovery, and water uptake in the study environment.

Technical Abstract: There is a gap in our understanding of grain sorghum [Sorghum bicolor (L.) Moench] abovegroundcrop production and soil resource (water and N) use in response responses to different crown root angles (CRA) in any pedoclimatic conditions. CRA is used as a proxy for different root system architectures in field conditions. Therefore, we selected grain sorghum genotypes previously classified to exhibit ‘shallow’ (' 40.5) and ‘steep’ (' 59.3) CRA from a diverse panel of 130 recombinant inbred lines to evaluate aboveground and belowground responses to CRA under different agronomic practices. These lines were planted as architectural monocultures and compared with a rooting architecture diversity treatment (‘shallow’, ‘intermediate’ (' 47.4), ‘steep’) receivingat four N rates (0, 20, 100, and 200 kg N ha-1) for two years in Experiment I. Similarly, the monocultures ‘shallow’ and ‘steep’ were compared to two rooting architecture diversity treatments (‘mix2’ and ‘mix10’) under two water regimes (irrigated vs. rainfed) for two years in Experiment II. Yield, other aboveground plant traits, soil water and N dynamics were evaluated. In Experiment I, increasing N application rate positively influenced all the aboveground traits measured, while diversity in rooting architecture had minimal or no impact on crop N uptake and other parametersonly affected seed weight and grain N concentration. In Experiment II, the ‘shallow’ CRA produced 15% greater harvest index compared with the ‘steep’ phenotype and there were no differences observed with either of the mixed treatments. The ‘steep’ CRA exhibited the highest grain N concentration, which was 1.49 and 1.59 g N kg-1 in 2016 and 2017, respectively, but rooting architecture diversity did not influence N uptake at harvest. The ‘mix2’ treatment had an average of 42% less drainage than the ‘shallow’ treatment during the 2017 season. There were no yield benefits or penalties associated with different CRA. The results of Experiment II indicated that, while root system architecture did influence a variety of soil response variables, including water drainage and NO3-N leaching below the rootzone, the trends across CRA treatments and years made the results largely inconclusive. Few studies have been conducted on this topic, some showing positive outcomes, but rResults of these studies of our two field experiments showed limited aboveground benefit of diverse and contrasting CRA to sorghum productivity, N recovery, and water uptake when grown in coarse-textured soil.