Effect of plant density on agronomic traits and forage quality forSorghum bicolor×S. sudanense

This study aimed to discover the differences in agronomic traits and forage quality at different plant densities of Sorghum bicolor×S. sudanense. A field small-plot experiment was conducted in the Haihe lowland plain, in which ‘Jicao 1’ and ‘Jicao 2’ were used for photoperiod insensitivity and photoperiod sensitivity of the experimental material, respectively. These correlative characteristic indexes, including the agronomic traits and forage quality, were analysed at different plant density treatments during the individual stages of heading, flowering, and milk. These results showed that the stem diameters of ‘Jicao 1’ and ‘Jicao 2’ at the low plant density (60 00075 000 plant·ha-1) were significantly higher than the high plant density (300 000375 000 plant·ha-1) from the heading to the milk stage (P<0.05), whereas there was no significant differences in the plant height, leaf number, ratio of stem∶leaf, and dry matter content (P>0.05). There was no significant differences in the dry yield of ‘Jicao 1’ under different treatments (P>0.05), but the content of crude protein and the relative feed value of ‘Jicao 1’ at the 150 000 plant·ha-1 were significantly higher than at 75 000 plant·ha-1 during the milk stage (P<0.05). The hay yield of ‘Jicao 2’ at the 300 000 plant·ha-1 was significantly higher than at 120 000 plant·ha-1 (P<0.05), but there was no significant differences between the treatment of 120 000 plant·ha-1 and other treatments on the content of forage quality for ‘Jicao 2’ during the milk stage. According to the comprehensive analysis, the suitable plant density of the photoperiod insensitive Sorghum bicolor×S. sudanense was 150 000 plant·ha-1, and the photoperiod sensitive variety was 120 000 plant·ha-1 when cutting during the milk stage in the Haihe lowland plains.