Root growth characteristics of millet cultivars and sorghum hybrids under increasing levels of soil compaction

Soil compaction negatively affects the physical properties of soil. The study of plants with the potential for mechanical loosening of soil is important for improving soil management and crop yield. In this context, the millet and sorghum are used as an alternative crop in the off-season in the mainly agricultural soil tropical. These roots can be a alternative to of soil mechanical loosening and avoiding mechanic tillage practices and keep soil conservation. Based on this, we assessed the aerial and root growth of millet and sorghum cultivars under different levels of soil compaction. The experiment was conducted in greenhouse conditions using a completely randomized design with four replicates. The treatments comprised of four cultivars of millet (ADR300, ADR500, BN2 and BRS1501) and two sorghum hybrids (Cober crop Atlantica and Monsanto) at four levels of subsurface soil bulk density (1.34, 1.53, 1.72, and 1.81 Mg m-3). We measured the root dry matter, root length density, mean root diameter for the upper, compacted and lower layers, and also the total dry matter. At soil bulk density 1.72 Mg m-3, both sorghum hybrids showed higher aerial dry matter production. At the highest level of soil bulk density, roots accumulated in the upper layer. Millet cultivar BN2 showed a decrease in root dry matter with increasing density in the compacted layer. All millet cultivars exhibited similar average root diameter at higher levels of compaction, except Millet ADR500 that showed less root diameter in the Upper compacted layer. Cober crop showed potential for soil decompaction, indicating the potential of this sorghum hybrid to soil mechanical loosening in the tropical soils