Xiaoxu Yu

This study investigated the differences in stem and leaf growth characteristics of Medicago sativa and Bromus inermis in the Jiaozhou region of China during 2019–2020 under three different planting modes of the two forages: monoculture, mixed species sowing in the same rows, and mixed species sowing in alternating rows. No special management of the experimental plots was carried out in this study to simulate as much as possible the growth of forages in their natural state. The stem and leaf characteristics influencing the dry matter weight were calculated using grey correlation. These characteristics included leaf length, leaf width, leaf thickness, leaf area, leaf fresh weight, stem length, stem diameter, stem fresh weight, stem–leaf ratio, fresh matter yield, dry matter yield, and protein yield of M. sativa and B. inermis under different sowing methods in different years. The results showed that the weight pattern of the characteristics affecting the yield of M. sativa and B. inermis production was leaf area > stem diameter > leaf length > stem length > leaf width > leaf thickness, leaf area > leaf length > stem length > leaf width > leaf thickness > stem diameter. Considering all the growth factors, the production capacity was ranked as mixed sowing in alternating rows > mixed sowing in same rows > monoculture. Thus, the suitable mode for M. sativa–B. inermis sowing was mixed sowing in alternating rows.

Belowground root systems under pasture intercropping exhibit complex interactions, and the root interactions of different intercropping combinations are still poorly understood. Therefore, in this work, two perennial and annual herbages were intercropped in pairs and evaluated at a ratio of 1:1. The root morphology and topological structure differed significantly with intercropping combinations. (1) Compared with other cropping patterns, the mean root diameter (RD) of intercropped alfalfa (Medicago sativa L.) and common vetch (Vicia sativa L.) increased notably. The root surface area (RSA), root volume (RV), and mean RD increased significantly when oat (Avena sativa L.) was intercropped with alfalfa. Similarly, the RSA and RV increased in intercropped oat, intercropping relative to monocropping. (2) The forage topological index of the intercropping system was close to one, which was close to that of the herringbone branching. Additionally, the intercropping system had a lower intensity of underground root competition. The root system of the different forage intercropping combinations tended to transition to dichotomous branching. (3) The correlations between root parameters differed according to forage species. Therefore, different intercropping combinations had different belowground root levels of competitiveness and interactions, thereby changing the resource competition environment.