Optimizing nutrient management protocol for <i>Ophiopogon japonicus</i>-corn intercropping: impacts on growth, yield, and medicinal quality

<i>Ophiopogon japonicus</i> is a valuable medicinal plant commonly intercropped with corn due to limited arable land in its primary cultivation areas. Optimizing fertilization management to enhance both crop yields and medicinal quality is a key research focus. This study investigates the effects of different fertilization treatments-nitrogen sources (urea and ammonium nitrate), micronutrient supplementation (magnesium and manganese), and phosphorus-potassium (P+K) fertilization-on the growth, yield, and medicinal quality of <i>O. japonicus</i> and corn in an intercropping system. A randomized complete block design was employed to evaluate eight treatments. Agronomic traits, biomass production, and medicinal quality indicators were analyzed using cluster analysis, correlation analysis, and principal component analysis (PCA). Results showed that nitrogen source significantly affected corn height, with ammonium nitrate outperforming urea. Micronutrients and P+K had significant interactive effects on stem diameter and leaf development. Fresh biomass and silage yield were primarily influenced by nitrogen source and P+K, while stem biomass was affected by micronutrient supplementation. The highest corn yield and biomass were recorded in treatments T5 (urea + P + K), T7 (urea + Mn + Mg + P + K), and T8 (ammonium nitrate + Mn + Mg + P + K). For <i>O. japonicus</i>, micronutrient applications significantly increased tuberous root numbers, while P+K fertilization promoted plant height and fibrous root growth. All three fertilization factors significantly impacted tuber biomass, the main determinant of medicinal yield. T8 showed the highest overall yield of <i>O. japonicus</i>, followed by T5 and T7. Medicinal quality evaluation through cluster analysis and PCA identified T5 as the optimal treatment for enhancing key medicinal components. The optimal strategy for maximizing yield in the intercropping system includes ammonium nitrate (150 kg N/ha), magnesium sulfate (45 kg/ha), manganese sulfate (15 kg/ha), superphosphate (75 kg P₂O₅/ha), and potassium sulfate (450 kg K₂O/ha). For improving medicinal quality, the best treatment includes urea (150 kg N/ha), superphosphate (75 kg P₂O₅/ha), and potassium sulfate (450 kg K₂O/ha). Future studies should assess the adaptability of this intercropping system across different soil and climatic conditions. Incorporating precision agriculture technologies may further refine fertilization strategies, while long-term monitoring is recommended to evaluate impacts on soil health and environmental sustainability.