Abstract:

To determine the optimal inter-row planting ratio of alfalfa （Medicago sativa） and smooth brome （Bromus inermis） for cultivation in the semi-arid region of Ningxia， a field study was conducted with single-crop alfalfa （CK_M） and smooth brome （CK_B） as controls. The treatments consisted of five different inter-row planting ratios of M. sativa （M） and B. inermis （B）： 3∶1 （M₃B₁）， 2∶1 （M₂B₁）， 1∶1 （M₁B₁）， 1∶2 （M₁B₂）， and 1∶3 （M₁B₃）. The agronomic traits and nutritional quality of both species and soil nutrient contents were measured and analyzed under these different planting patterns. It was found that the 2∶1 inter-row planting ratio （M₂B₁） achieved the best performance in terms of yield， quality， and soil nutrient accumulation. Compared with CK_M， the M₂B₁ treatment increased the number of alfalfa branches by 18.36%. Compared with CK_B， the M₂B₁ treatment enhanced smooth brome plant height and leaf area by 22.40% and 37.03%， respectively. The mixed hay yield under M₂B₁ reached 17.70 t·ha^-1， comparable to that of CK_M. In terms of nutritional quality， the M₂B₁ treatment increased the crude protein content by 33.83% and decreased the neutral detergent fiber content by 5.12%， compared with CK_B. Soil analysis revealed that the M₂B₁ treatment increased the soil organic matter content by 2.13% and 3.90% compared with that in CK_M and CK_B， respectively， and the alkaline-hydrolyzable nitrogen content by 16.53% and 37.33%， respectively. The results of a redundancy analysis indicated that mixed yield was positively correlated with soil available potassium and alkali-hydrolyzable nitrogen contents. In conclusion， the 2∶1 inter-row planting ratio of alfalfa and smooth brome in Ningxia optimized land resource utilization efficiency， productivity， and soil nutrient accumulation.

Key words: Medicago sativa, Bromus inermis, inter-row planting, production performance, soil nutrients