The agronomic traits of dual-purpose sorghum and millet at the jointing stage in response to soil salinity gradients in the Hetao Irrigation District of Inner Mongolia

The planting of grain-forage crops is important for the sustainable development of agriculture and animal husbandry in the Hetao Irrigation District of Inner Mongolia. In this study, two sorghum varieties ('F438' and '2562') and two millet varieties ('Zhangza 19' and 'Zhangza 13') were used as experimental materials to study the agronomic traits at the jointing stage in response to different soil salinity gradients in Wuyuan County, in Hetao Irrigation District, Inner Mongolia. Gradient analysis and correlation analysis were used to examine the relationships between the agronomic characteristics and soil electrical conductivity (EC). The results showed that the EC of soil planted millet was lower than that of soil planted sorghum at the jointing stage. With increased soil EC, the number of visible leaves of millet varieties and sorghum varieties decreased significantly, indicating that soil EC inhibited the both crops growth. A high level of soil EC significantly also inhibited the plant height and stem diameter of both crops. Furthermore, with increased soil EC, the chlorophyll content of the leaves of both crops decreased, but the chlorophyll content of sorghum was less affected by soil EC than that of millets. Correlation analysis showed that the stem diameter, plant height, leaf area, and leaves number of both crops were significantly negatively correlated with soil EC at the elongation stage. The millet variety 'Zhangza 19' had a higher tolerance to soil salinity and stronger potential adaptability for planting in saline-alkali land. This study provides a scientific basis for exploring the adaptive mechanisms of dual-purpose crops planted in saline-alkali land. This study also provides important theoretical guidance for the optimization of traditional agricultural planting patterns and the sustainable development of animal husbandry in the Hetao Irrigation District of Inner Mongolia.