Effects of water and phosphorus on root growth and morphological characteristics of switchgrass in the establishment year

To clarify the relationshiops of water and phosphorus with root growth and morphology could provide the basis for water and fertilizer management during the grassland construction of switchgrass (Panicum virgatum) in dry region. A pot experiment was conducted using split-plot design, and the main plot was soil water regimes high water: 80% FC (field capacity) and low water: 40% FC, while the subplot was phosphorus (P) treatments (0, 0.05 and 0.1 g P₂O₅ per kg dry soil). The shoot and root biomass production, and root morphology of switchgrass under different treatments were measured at the end of the growth period. Results showed that regardless of P application, switchgrass had significantly (P < 0.05) higher shoot and root biomass, total root length (TRL), root surface area (RSA) and root average diameter, but lower water use efficiency and specific root length under high soil water regime than under low soil water regime. Under high soil water regime, P application significantly increased shoot and root biomass production, and TRL and RSA. Under low soil water regime, P application significantly increased water use efficiency of switchgrass, and 0.1 g P₂O₅ per kg dry soil application significantly promoted TRL, RSA and root growth in 0～0.5 mm diameter. All these indicated that under low soil water conditions, rational P application could improve the root absorptive capacity and drought adaptability of switchgrass in the establishment year.