Reasons for promoting rhizosphere nutrient absorption and utilization of Atractylodes lancea by intercropping with maize

Previous studies have found that intercropping with maize can mitigate the challenges associated with continuous cropping of Atractylodes lancea with alterations in nutrient conditions being a crucial factor. To explore the effect of A. lancea||maize intercropping on absorption and utilization of nutrients in the rhizosphere of A. lancea, through a 2-year field experiment employing different rhizosphere separation treatments. Four treatments were implemented: A. lancea monoculture (A), A. lancea||maize intercropping without separation (AI), A. lancea||maize intercropping with nylon separation (AN), and A. lancea||maize intercropping with a plastic film (AP). The biomass of A. lancea and the contents of four volatile oil components were measured at harvest. The contents of nitrogen, phosphorus, and potassium in the rhizomes of A. lancea, and rhizosphere soil pH, contents of organic matter and nutrients were compared and analyzed. The results indicated that the fresh weight of A. lancea rhizomes in the AI treatment was significantly 21.5% higher than that in treatment A and 69.1% higher than that in treatment AP (P<0.05). Additionally, the AN treatment demonstrated a 10.7% increase compared to the A treatment and a 54.2% increase compared to the AP treatment in A. lancea rhizomes (P<0.05), respectively. The content of β-eudesmol in the AI treatment was significantly higher than that of the A and AP treatments by 128.4% and 205.6%, respectively (P<0.05). The atractylodin content in the AI treatment was significantly higher than those in the A and AP treatments by 875.0% and 97.7% (P<0.05), respectively; and that in the AN treatment was significantly higher than those in the A and AP treatments by 764.0% and 75.0% (P<0.05), respectively. The total content of the four volatile oil components in A. lancea in the AI and AN treatments was significantly higher than that in the A and AP treatments by 82.8%−210.3% (P<0.05), indicating that the underground rhizosphere interaction of A. lancea||maize intercropping played an important role in promoting biomass and volatile oil accumulation in A. lancea rhizome. Compared with the A and AP treatments, the AI and AN treatments decreased the rhizosphere soil pH of A. lancea by 0.4%−6.3%, and the soil organic matter increased by 13.5%−48.1%. While the AI treatment significantly increased the alkali-hydrolyzable nitrogen content by 32.8% and 36.2%; AN treatment significantly increased the available potassium content by 51.5% and 46.7%, and the available phosphorus content by 78.3% and 86.6%, respectively, compared with A and AP treatments. These findings demonstrate that the rhizosphere interaction between A. lancea and maize enhances the rhizosphere acidification level of A. lancea and stimulates soil nitrogen, phosphorus, and potassium compared with no rhizosphere interaction. Correlation analysis showed that atractylon content was positively correlated with nitrogen, phosphorus, and potassium contents in the rhizomes of A. lancea; and nitrogen, phosphorus, and potassium contents in the rhizosphere soil. Atractylodin content was positively correlated with potassium content in the rhizomes of A. lancea. Compared with the A and AP treatments, the AI treatment increased the phosphorus absorption efficiency of A. lancea by 23.4% and 30.0%, respectively. The phosphorus utilization efficiency significantly increased by 224.6% and 43.6% under the AI treatment, and by 157.0% and 13.6% under the AN treatment, compared with the A and AP treatments, respectively. The nitrogen and potassium utilization efficiency was significantly increased by 131.3%−222.2% under the AI and AN treatments compared with the A treatment, indicating that the rhizosphere interaction of intercropping crops promotes phosphorus absorption and improves the nitrogen and potassium utilization of A. lancea. In conclusion, in A. lancea||maize intercropping system, the underground rhizosphere interaction (under AI and AN treatments) promoted the absorption and utilization of nutrients of A. lancea compared to no rhizosphere interaction (under A and AP treatments), thereby increasing the yield of A. lancea and affecting volatile oil accumulation in the rhizomes of A. lancea. This study reveals that the underground rhizosphere interaction in A. lancea||maize intercropping is a key factor that promotes nutrient absorption and utilization of A. lancea and provides an important reference for promoting the ecological diversity of the planting mode of medicinal plants.