Effects of Nitrogen Reduction Combined Microbial Fertilizers on Foliar Yield and Quality of Ginkgo biloba, Soil Properties and Microbial Community

Abstract

: The proportion of nitrogen (N), phosphorus (P), and potassium (K) in the soil could regulate plant yield and secondary metabolism. However, extensive chemical fertilizer utilization has reduced soil fertility and increased soil compaction, and even caused environmental pollution. Applying microbial fertilizers (MF) could improve soil structure and the environment. This work aimed to reveal the effects of N reduction and combined MF on Ginkgo biloba growth, soil properties, and microbial communities, and illustrate their interaction roles in improving Ginkgo leaf yield and flavonoid content. A field experiment with different fertilizer treatments, including low N, normal P-K (T1), low N, high P-K (T2), T1 + MF (T3), T2 + MF (T4), and MF (T5), was applied for Ginkgo trunk-cutting seedlings. Our data showed that the treatments of T2 and T4 both significantly increased the levels of net photosynthetic rate, flavonoid content, and yield in the leaves, and elevated the levels of nitrate-N, availability of P and K, and the activities of urease and acid phosphatase in the rhizosphere soil (RS). T2 treatment decreased bacterial diversity, increased the relative abundance (RB) of Nitrospirota and Gemmatimonadota in RS, and enhanced nitrate denitrification and nitrite respiration. However, T4 treatment significantly increased the RB of Acidobacteria bacterium WWH8 and delta-proteobacterium , and improved microbial bacterial metabolism of nitrogen, thiosulfate, photosynthesis, etc. Therefore, the reasonable proportion of NPK fertilizer combined with MF could regulate the nutrient use efficiency, enhance flavonoid synthesis, and raise leaf yield in Ginkgo forests by improving the bacterial community composition. Our work provided evidence for the benefits of fine-regulating NPK proportion and integrating MF measures to promote plant growth and secondary metabolism. Meanwhile, this also provided references for the in-depth exploration of the mechanistic interactions between rhizosphere organisms and plants.