Effects of mixed sowing ratio on root properties of Medicago sativa and Agropyron cristatum

In the present study, we clarified the root adaptation strategies of Medicago sativa and Agropyron cristatum in northern Xinjiang. Medicago sativa and A. cristatum were mixed with the sowing ratios of 3 : 7 (DH1), 4 : 6 (DH2), 5 : 5 (DH3), 6 : 4 (DH4), and 7 : 3 (DH5), respectively. With DM and DB as controls and root dry weight, root volume, root surface area, root length, root average diameter, and root tip number as measurement indices, the least significant difference method (LSD) was used to analyze the root attribute parameters of each treatment. Bivariate correlation analysis was used to analyze the correlation of each measurement index. The results demonstrated that the following: 1) among the four soil layers, the total root volume and total root surface area of each treatment were greater than those of DM and DB. Except for the root surface area of DH₅ in the 30－40 cm layer, all others were the most representatives of DH₃, indicating that mixed sowing significantly increased the total root volume and root surface area of the forage. 2) The average root diameter of alfalfa was larger than that of dip grass and than that of total roots. The differences among the soil layers varied. The average diameter of 0－10 cm was DH₄, the average diameter of 10－20 cm–DH₅, and the average diameter of 20–30 and 30–40 cm was DH₃ and DH₅. The overall regularity in the number of root tips was weak. 3) The roots were largely distributed in the 0－20 cm soil layer. With an increase in the leguminous forage ratio in the mixed sowing ratio, the total root length, total root surface area, and total root volume first increased and subsequently decreased, and DH3 peaked. 4) Root length was significantly correlated with root dry weight, root surface area (P < 0.05), and was significantly correlated with root volume (P < 0.01). Therefore, among the treatments, the root parameters of DH3 were significantly better than those of other treatments and Unicast, indicating a strong advantage. Better root parameters lead to more water and nutrient space, which contribute to the growth of the aboveground grasses.