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

There is a gap in our understanding of grain sorghum [Sorghum bicolor (L.) Moench] crop production and soil resource (water and N) use in response 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' (measured angle 40.5) and 'steep' (measured angle 59.3) CRA from a diverse panel of 130 recombinant inbred lines to evaluate aboveground responses to CRA under different agronomic practices. These lines were planted as architectural monocultures and compared with a rooting architecture diversity treatment ('shallow', 'intermediate' (measured angle 47.4), 'steep') at 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 di-versity treatments ('mix2 ' and 'mix10 ') under two water regimes (irrigated vs. rainfed) for two years in Exper-iment 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 rooting archi-tecture had minimal or no impact on crop N uptake and other parameters. There were no yield benefits or penalties associated with different CRA. The results of Experiment II indicated that, while root system archi-tecture 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 results of these studies showed limited benefit of diverse and contrasting CRA to sorghum productivity, N recovery, and water uptake when grown in coarse-textured soil.