Interspecific competition, ecological benefits, and productivity in maize/alfalfa strip intercropping systems on the Loess Plateau of China

To overcome the global challenges of arable land scarcity and the dual demands of food security and sustainable livestock development, a maize ( Zea mays L.)/alfalfa ( Medicago sativa L.) intercropping system can be used as a strategy to address the reduction in cultivated land and increase production potential and resource efficiency. However, while the maize planting density remains unchanged, the maize/alfalfa intercropping system productivity and interspecific competition are still unclear on the Loess Plateau. This study aimed to evaluate the system dry matter yield, economic yield, crude protein yield, food equivalent unit yield, and starch yield performance under interspecific competition. To address this, a two-year field experiment (2023–2024) was conducted on China's Loess Plateau, evaluating five intercropping row ratios (M 2 A 5 , M 2 A 7 , M 2 A 9 , M 2 A 11 , and M 2 A 13 : two maize rows intercropped with 5, 7, 9, 11, or 13 alfalfa rows, respectively) against sole maize (SM). The results demonstrated that the M 2 A 9 system achieved optimal trade-offs, increasing total economic yield (EY: 27.22 t ha −1 ), crude protein yield (CPY: 4.58 t ha −1 ), and food equivalent unit yield (FEUY: 34,750 FEU ha −1 ) by 26.33 %, 39.76 %, and 5.25 %, respectively, despite slight reductions in dry matter (DMY: −2.66 %) and starch yields (STY: −15.47 %). Productivity metrics followed a hump-shaped response to maize plant density, peaking in the M 2 A 9 treatment, which also exhibited the highest land equivalent ratio (LER: 1.38 in 2023 and 1.13 in 2024) and land use efficiency (LUE: 206.88 % in 2023 and 151.58 % in 2024). Competitive dynamics revealed that maize was the dominant species (a competitive ratio >1 and aggressivity >0), and was driven primarily by intraspecific competition, whereas alfalfa faced stronger interspecific competition. Economically, the M 2 A 9 treatment outperformed the other systems, with the highest monetary advantage index (MAI), relative net return index (RNRI), and net benefit (3204 $ ha −1 ). These findings highlight maize-alfalfa intercropping as a viable strategy for reconciling productivity, ecological sustainability, and profitability, particularly under the M 2 A 9 configuration. We advocate its adoption to support smallholder incomes and advance agro-pastoral sustainability in similar semiarid regions. • M2A9 intercropping boosts economic yield (+26 %) & protein yield (+40 %). • Peak land use efficiency (LER:1.38) achieved with M2A9 configuration. • Maize dominates via intraspecific competition in balanced systems. • M2A9 maximizes net profits (3204$ ha −1 ) sustainably. • Optimal row ratio reconciles productivity & ecological benefits.