Effects of quinoa varieties with different plant height and growth cycle on root distribution, soil nutrient absorption, and productivity of peanut under quinoa–peanut relay intercropping system in saline-alkali soil

• Peanut intercropping with short-stemmed quinoa variety has lower underground competition intensity. • Early-maturing quinoa variety enhances the “recovery growth effect” of intercropped peanuts. • Short-stemmed and early-maturing varieties is more beneficial for the growth and yield of intercropped peanuts. Quinoa–peanut relay intercropping is a potential practice in saline-alkali land; however, quinoa varieties exhibit considerable variability, and a paucity of information regarding suitable varieties of quinoa for intercropping with peanuts. A field experiment with three intercropped peanut treatments (PSE, PMM, and PTL) with quinoa varieties of short-stemmed and early-maturing (QSE), medium-stemmed and medium-maturing (QMM), and tall-stemmed and late-maturing (QTL) was conducted in 2021–2022 to elucidate the effects of quinoa varieties on the root distribution, soil moisture content (SMC), electrical conductivity (EC), nutrient (N, P, and K) absorption, and pod yield of peanuts. The results showed the pod yield, pod dry weight, biomass, and 100-fruit weight of peanut under PSE were the highest, followed by PMM, and PTL was the lowest. The pod yield of PSE was 6.03–21.16% higher than that of PMM and PTL in 2021 and 2022. In the co-growth period of quinoa and peanut (CGP), the main stem height, branch number, leaf area (LA), dry matter weight, and nutrients absorption of peanut plants under PSE and PMM were all significantly higher than PTL; but no difference was observed between PSE and PMM. In the solo-growth period of peanut (SGP), the plant traits (except for the main stem height) and nutrient absorption of peanut under PMM were worse than PSE, and PTL was the worst, which was consistent with the variation of root length density (RLD) of peanuts. Meanwhile, PSE had the highest SMC at soil depths below 10 cm, nutrient contents in rhizosphere soil (K + , NO 3 − , NH 4 + , PO 4 3− , and TOC), also EC and Na + contents compared with PMM and PTL. The RLD of peanut, SMC, EC, and nutrient contents in rhizosphere soil of peanuts were negatively correlated with the RLD of quinoa. Therefore, intercropping peanut with short-stemmed and early-maturing quinoa variety is more conducive to increasing peanut yield in saline-alkali soil.