Abstract: In order to solve the problem of low utilization efficiency of slope beam land and select the suitable planting mode, an intercropping experiment of pumpkin and oil sunflower was conducted at the Zhangbei Station of Heibei Agricultural University in 2020. Four modes of pumpkin and oil sunflower intercropping were designed, including sole cropping of pumpkin (Sp) and oilsunflower (So), intercropping with one row of oil sunflower (IC₁), and intercropping with two rows of oil sunflower (IC₂) between pumpkin rows. We examined root distribution in tillage layer and analyzed the relationships between below and above-ground of pumpkin and oil sunflower by digging roots by layers, combined with ScanMaker-i800 and root analysis system during harvest. The results showed that oil sunflower took an advantage over pumpkin in the intercropping system, as indicated by the fact that root characters of intercropping oil sunflower was better than that of oil sunflower sole cropping. Root fresh weight, dry weight, root length, root surface area and volume of oil sunflower in treatments of pumpkin intercropping with one row (IC1) and two rows oil sunflower (IC2) were significantly increased by 87.72% and 45.49%, 149.52% and 83.39%, 25.30% and 26.62%, 19.61% and 14.23%, 53.24% and 43.89% than that in treatment of oil sunflower sole cropping (So), respectively. As oil sunflower was dominant in nutrient and water uptake in the intercropping system, roots of intercropping pumpkin were weaker than that of pumpkin sole cropping. Root fresh weight, dry weight, root length, root surface area and volume of pumpkin in sole cropping (Sp) were significantly increased by 80.25% and 140.37%, 49.73% and 92.96%, 1.83% and 12.80%, 3.90% and 26.04%, 22.15% and 21.76% than that in IC₁ and IC₂ in 0-40 cm soil layer, respectively. The roots and aboveground biomass of intercropping pumpkin were significantly lower than that of monoculture, while opposite patterns were observed for oil sunflower. Root density of pumpkin decreased by power function with increasing soil layers, while it decreased by exponential function in oil sunflower. Our results suggest that pumpkin monoculture is the suitable planting method in rain-fed dryland farming.

Key words: pumpkin, oil sunflower, intercropping, root system, yield.