Comprehensive analysis of nutrient partitioning and microbial communities in pear orchards: effects of tree age and...

Pear tree nutrient requirements vary across growth stages. The spatial distributions of soil nutrients and microbial communities were analyzed to elucidate the nutrient demands at different growth stages, investigate the relationship between soil microorganisms and nutrients, and provide a theoretical basis for fertilization and soil management practices in pear orchards.

Distinct temporal and spatial patterns in nutrient dynamics were observed. With increasing tree age, the leaf calcium (Ca) content initially increased then decreased, peaking at 30.96 g·kg⁻¹ in 46-year-old trees. The leaf copper (Cu) content progressively increased, reaching its highest concentration (15.16 mg·kg⁻¹) in trees (> 100 years). The relative abundances of key bacterial phyla, Actinobacteria and Acidobacteria, reached their maxima (19.88% and 20.4%, respectively) in 4-year-old orchards before slightly declining. Spatial analysis of mature orchards revealed that the soil phosphorus (P) and potassium (K) contents decreased with increasing distance from the tree trunk, whereas the boron (B), zinc (Zn), and manganese (Mn) contents increased. Comparative analysis with adjacent long-term unplanted soils revealed that pear tree cultivation significantly depleted soil Ca, magnesium (Mg), iron (Fe), and Mn, whereas Cu and Zn levels increased, suggesting a high tree demand for the former group and an application rate of Cu and Zn fertilizers exceeding the tree absorption capacity. Within tree tissues, the nitrogen (N) and P contents were highest in 1- and 2-year-old branches, whereas Ca, Mg, Fe, B, and Mn accumulated predominantly in perennial old roots. Significant positive correlations were identified between several leaf and soil elements. Furthermore, soil nutrient availability was linked to microbial diversity: soil P and Zn contents were positively correlated with the bacterial aroma index. Soil Mg, Cu, and Zn were positively correlated with the bacterial ACE index; and the soil N content was positively correlated with the fungal Simpson index.

Soil microbial communities in pear orchards are associated with P, Ca, and Zn. Nutrient elements in pear trees such as Ca, Mn, B, Mg, and Fe, which are difficult to transport and tend to accumulate in root tissues; thus, foliar application is recommended for their supplementation.