Root responses of maize to spatial heterogenous nitrogen and phosphorus

The resourcerich regions (patches) of nitrogen or phosphorus usually exist independently in soil, and understanding how roots respond to spatial heterogenous nitrogen and phosphorus has important implications for exploring biological potential through rhizosphere management to improve the uptake efficiency of nitrogen and phosphorus by roots, and realizing efficient acquisition and utilization of nitrogen and phosphorus resource. A pot experiment was carried out to reveal the effect of three modes of localized nitrogen and phosphorus supply (nitrogen and phosphorus uniform supply, local supply in separation, and local supply in combination) on the root growth and distribution, as well as nitrogen and phosphorus uptake by maize. The results show that localized application of nitrogen and phosphorus significantly increased the root dry weight regardless of supply pattern in separation or in combination. Compared with the uniform supply treatment，local supply in combination significantly increased total root length, root dry weight and root mass ratio by 28%, 66% and 31%, respectively, but decreased phosphorus uptake by 35%. No significant difference was observed in shoot dry weight and nitrogen uptake. By contrast, local supply in separation significantly increased root and shoot dry weight by 55% and 55% respectively, enhanced nitrogen and phosphorus uptake by 58% and 81% respectively, but there was no significant difference in total root length and root mass ratio. In addition, compared with the nitrogen supply patches, the phosphorus supply patches stimulated the root growth significantly, indicating that maize tends to allocate more dry matter to phosphorus supply area than nitrogen supply area. It is concluded that maize can integrate the root responses to both nitrogen and phosphorus supply through altering root morphology and distribution under local nitrogen and phosphorus supply in separation relative to combination condition, to enhance the root acquiring ability for soil nitrogen and phosphorus resources, which provides an important foundation to optimize the spatial arrangement of nitrogen and phosphorus and nutrient resource management.