Effects of maize and soybean intercrop on maize root morphological traits and its nitrogen and phosphorus nutrient absorption

【Objective】To investigate the changes of maize root morphology and its corresponding relationship with absorption of nitrogen and phosphorus nutrient in maize intercrop，so as to provide a theoretical basis for the optimal management of nitrogen and phosphorus nutrient absorption in maize intercrop system.【Method】A field trial of maize and soybean intercrop was conducted，with two cropping systems，maize monocrop and maize and soybean intercropping set to operate a quantitative analysis on 5 indexes of maize root morphology，root length，root surface area，root volume，average root diameter and root tip number，and to determine the contents of total phosphorus and nitrogen and calculated how much nitrogen and phosphorus were absorbed in plants.【Conclusion】At the belling，tasseling and maturing stages，compared to the monocropped maize，the intercropping maize could promote the growth of maize and significantly increase the grain yield by 35.10%（P<0.05，the same below）. The nitrogen content of intercropped maize significantly increased by 10.54% at tasseling stage，and the phosphorus content significantly increased by 12.81% and 12.10% at belling and maturing stages compared to monocropped maize，respectively. At the three growth stages，the nitrogen and phosphorus absorption per plant of intercropped maize increased significantly by 78.71%，26.06%，39.26% and 88.15%，23.02%， 46.42% respectively. Compared with monocropped maize，the root length of intercropped maize increased significantly by 23.90%，14.91% and 27.49% at the three growth stages，the root surface area and root volume increased significantly by 18.41%，21.46% and 33.39%，31.11% at the tasseling and maturing stages，and the number of root tips increased significantly by 15.11% and 14.72% at the belling and tasseling stages，respectively，while the average root diameter without significant variation（P>0.05）. Correlation analysis and stepwise regression analysis results showed that maize nitrogen and phosphorus nutrient absorption was closely correlated with root morphological parameters. Root length and root dry weight had the biggest influence on maize plant nitrogen absorption while root volume and root dry weight had the biggest influence on maize phosphorus absorption.【Conclusion】Compared to maize monocrop，intercrop can increase maize root length, root surface area, root volume，and root tip number，decrease average root diameter and significantly increase maize plant nitrogen and phosphorus nutrient absorption. The root morphological changes are one of important adaptive mechanisms driving the increase in nitrogen and phosphorus absorption in intercropped maize.