Effects of biochar-based phosphate fertilizer on photosynthetic and fluorescence characteristics of Stipa krylovii

Fertilization is an important tool for the restoration of degraded grasslands, but biochar-based phosphate fertilizer is rarely studied in the improvement of natural grassland. In this study, we used Stipa sareptana var. krylovii as the project; six fertilization treatments were set up: Control (CK), diammonium phosphate (D), biochar (B), low application rate of biochar-based phosphate fertilizer (LBD), medium application rate of biochar-based phosphate fertilizer (MBD), and high application rate of biochar-based phosphate fertilizer (HBD), and determination of S. sareptana var. krylovii tiller number, biomass, and photosynthetic-fluorescence parameters. The results showed that the number of tillers in S. sareptana var. krylovii under HBD treatment was significantly higher than that in CK and D treatments. The biomass of HBD, MBD, and LBD treatments was significantly higher than that of the CK treatment. The relative variable fluorescence and primary quinone receptor (QA) reduced rate values of HBD and LBD treatments were significantly lower than those of CK treatment (P < 0.05), and the photochemical performance index and electron transfer rate values of HBD and LBD treatments were significantly higher than those of CK treatment (P < 0.05). The net photosynthetic rate, transpiration rate, and water use efficiency of HBD treatment showed an increasing trend. Principal component analysis showed that the photochemical performance index and QA reduced rate were important photosynthetic physiological indicators that demonstrate the response to the effect of biochar-based fertilizer application. The results of the comprehensive evaluation showed that the best effect on the photosynthetic-fluorescence characteristics of S. sareptana var. krylovii were attained via HBD and MBD treatments, which promoted the growth of S. sareptana var. krylovii, and had a certain positive effect on the restoration of the degraded grassland. Thus, taking S. sareptana var. krylovii as the constructive species the significance and application value of biochar-based phosphate fertilizers for improving the productivity and ecological function was demonstrated.