Effects of root characteristics on phosphorus use efficiency of forage grass under different phosphorus supply levels

To investigate the effects of different soil phosphorus supply levels on phosphorus use efficiency, root morphology, and rhizosphere microenvironment characteristics of mixed forage grasses (Avena sativa and Vicia sativa) and to determine the relationship between root morphology, rhizosphere microenvironment characteristics and phosphorus use efficiency, a pot experiment was conducted with three soil phosphorus supply levels: high, medium, and low. The phosphorus use efficiency, nutrient competition ratio, soil phosphorus enrichment rate, root morphological characteristics, and rhizosphere microenvironment characteristics of the two mixed grass plants were measured. Relevant indicators were used to analyze the phosphorus use advantages of the use of forage grass in the legume-grass mixed-sowing system and to clarify the competition for phosphorus nutrients in the soil in the legume-grass mixed-sowing system with different phosphorus supply levels. The results were as follows: 1) The P content of the forage under the high-P treatment was significantly higher than that under the medium- and low-P treatments (P < 0.05), but the P use efficiency of forage under the low-P treatment was lower than that under medium-P treatment. 2) Significant differences were found in the morphological root characteristics of the forage under different soil phosphorus supply levels, but no significant difference were found in root configuration characteristics ( P > 0.05). 3) The soil pH value was ranked in the order of low P > medium P > high P treatments. The soil phosphatase activity was the lowest in the low-P treatment, and no significant difference was found between the high- and medium-P treatments ( P > 0.05). This study analyzed the phosphorus use efficiency of this mixed-seeding system under different phosphorus supply levels in the soil and exploring the possible pathways through which phosphorus transfer or sharing occurs between phosphorus-efficient and phosphorus-inefficient plants and their influencing factors to provide scientific information for the efficient use of phosphorus in these systems.