Peach [Prunus persica (L.) Batsch] is a fruit tree within the family Rosaceae. Peach fruit is rich in a variety of nutrients beneficial to the human body and it has become one of the most popular fruits due to its sweet and delicious taste and beautiful attractive appearance. The origin of the peach is China, which has a history spanning thousands of years (Liu et al., 2015). At present, China’s peach production ranks first in the world; it has increased from approximately 4.6 Mt. to approximately 16 Mt., an increase of approximately 248% in the past 20 years. China’s peach area harvested has increased from approximately 0.45 Mh to approximately 0.83 Mh, an increase of approximately 84% (FAO, 2022). With the rapid development of the peach industry and the demand for rural ecological environment governance, how to deal with a large amount of peach branch waste generated by pruning peach trees has become a difficult problem. Burning peach branch waste or stacking it in the field will cause greenhouse gas emissions, which can seriously endanger ecological balance and human health. Previous studies showed that peach branch waste can be used as raw material to extract and prepare a reinforcing agent and as a promising feedstock for ethanol production (Buratti et al., 2018; Wei et al., 2023). In agriculture, peach branch waste can be used as a substrate for oyster mushrooms (Yang et al., 2022). However, there is less research on the return of peach branch waste to the field. At present, peach branch waste is crushed mechanically and composted by adding livestock and poultry manure, biological agents, and straw decomposition agents to make peach organic fertilizer in many peach-producing areas in China. This process has formed a recycling mode in which peach branch waste is transformed into renewable resources, and then renewable resources are transformed into agricultural resources again. The conversion of discarded peach branches into organic fertilizer will significantly alleviate environmental pollution. Moreover, with the widespread utilization of peach branch organic fertilizer (PBOF), the local farmers will enjoy substantial economic benefits from the sale of these peach branch wastes.

Fertilization plays a vital role in enhancing agricultural production, serving as a crucial method to not only improve soil quality but also increase soil productivity (Yang et al., 2019). The increase in crop yield in recent decades has depended largely on chemical fertilizer (Geng et al., 2019; Iqbal et al., 2021); for example, suitable potassium fertilizer can often improve fruit quality (Crisosto and Costa, 2008). However, excessive and long-term application of chemical fertilizers has negative effects on ecosystems, including soil and water (Sun et al., 2015; Pirttilä et al., 2021). Excessive fertilization can lead to soil acidification and a decrease in soil organic matter (SOM) content, which directly affects crop growth and sustainable use of soil. Among them, SOM plays a critical role in maintaining soil fertility and productivity (Lin et al., 2019; Wu et al., 2020). To increase SOM content, improve soil quality, and enhance soil fertility, applying organic fertilizer is an excellent choice (Liang et al., 2014; Hua et al., 2020). Organic fertilizer treatment has been shown to significantly affect soil chemical properties, increasing SOM, total nitrogen (TN), and available phosphorus (AP; Ji et al., 2021). Moreover, the application of organic fertilizer alleviates soil acidification by adjusting the pH of the soil (Afreh et al., 2018). In the study of Ye J. H. et al. (2022), similar results were found, and the application of organic fertilizer stabilized the soil pH within the optimal range. Furthermore, the application of organic fertilizer has a good effect on yield and quality by improving soil nutrients, properties, and microecology (Liu et al., 2021).

Soil microorganisms are very active in the soil ecosystem, are involved in the decomposition of organic matter and nitrogen fixation, and play a crucial role in soil energy flow and the nutrient cycle (Morris and Blackwood, 2015; Nazaries et al., 2021; Wang T. et al., 2022). The soil bacterial community affects processes such as carbon cycling, litter decomposition, and soil fertility changes (Cao et al., 2021; Zhang H. H. et al., 2022). Fertilization has an impact on soil microbial abundance and community structure (Guo et al., 2020; Iqbal et al., 2022). Research by Wang et al. (2016b) showed that the application of bioorganic fertilizer had a significant effect on the structure and composition of the soil microbial community in apple orchards, such as increasing the relative abundance of the genera Bacillus, Lysobacter, and Pseudomonas. The difference is that the application of chemical fertilizer did not increase the relative abundance of Bacillus, Lysobacter, and Pseudomonas. There was a correlation between the abundance of soil microorganisms and yield; for example, the relative abundance of Bacillus had a positive correlation with yield. Similar results were obtained in another study (Wang et al., 2016a). In addition, the application of organic fertilizer increased nutrient availability and enhanced synergistic interactions between soil microorganisms, thereby promoting plant growth (Zhang et al., 2019). Li et al. (2021) found the different responses of bacterial communities to plant-derived and animal-derived organic fertilizer. The animal-derived organic fertilizer significantly increased the Richness index and Shannon index, while plant-derived organic fertilizer did not. Compared with animal-derived organic fertilizer, plant-derived organic fertilizer had a weaker influence on the abundance of each phylum level. Liu et al. (2020) showed that the Shannon index and Chao1 index did not increase with increasing organic fertilization levels. The relative abundance of Actinobacteria, Verrucomicrobia, and Armatimonadetes decreased with increasing organic fertilization levels. Moreover, the relative abundance of Pseudomonas increased with increasing organic fertilization levels. Overall, the influence of fertilizer categories and levels on soil microorganisms cannot be ignored.

Peach branch waste composting is an effective mode to improve the resource utilization of peach orchard waste. However, the effects of PBOF on soil properties and bacterial community, peach fruit quality and orchard yield and their relationship with each other have not been systematically studied. The main objectives of this study were to (1) study the effects of PBOF on soil properties and the soil bacterial community; (2) study the effects of PBOF on the quality and yield of peach fruit; (3) explore the potential correlation between soil properties and the soil bacterial community and peach fruit quality and yield; and (4) compare the effects of PBOF and commercial organic fertilizer. There were two main hypotheses: (1) peach fruit quality and yield are affected by the soil bacterial community and soil properties and (2) PBOF can achieve similar results to the application effect of commercial organic fertilizer. This study aimed to provide a theoretical basis for scientific fertilization, ensure the yield and quality of peach fruit, and reduce the environmental pollution caused by peach branch waste.

The results of this study showed that soil chemical properties changed significantly after the application of organic fertilizer. Specifically, the application of organic fertilizer (SDH, SKR, and SYT) significantly increased soil AN, AP, AK, and SOM compared to CK, which is consistent with findings from previous studies (Baldi et al., 2016; Kobierski et al., 2017; Su et al., 2021). This indicates that PBOF can enhance the nutrient availability as well as the fertility of the soil, which benefits the growth and development of plants. The increasing application levels of three types of organic fertilizers did not have a significant impact on AN, AP, AK, and SOM, except for AK in SYT.3 and SYT.4 treatments which were significantly higher than that of SYT.2 treatment, which may be related to the fact that organic fertilizers were applied for only 1 year (Table 2). In a two-year research study, there were significant differences between different organic fertilization levels in soil nutrients (Chen et al., 2022). Interestingly, all fertilization treatments did not have a significant effect on soil pH compared to CK, which disagreed with previous findings (Tang et al., 2020). This discrepancy might be due to differences in the soil type (Wei et al., 2017). By comparing the three organic fertilizers, it was found that the two PBOF had similar effects to commercial organic fertilizers in affecting soil chemical properties and improving soil nutrients.

In addition, the peach yield increased significantly after the application of organic fertilizer (Table 1). Similar results can be found in apple (Milošević et al., 2022), pear (Wang Z. H. et al., 2022), pear-jujube (Ye S. L. et al., 2022), red pitaya (Chen et al., 2022), and kiwifruit (Liu et al., 2020). In our study, the application of organic fertilizer also significantly increased the SSC/TA ratio of peach fruit (Table 1). The eating quality of peaches is mainly related to the sugar/acid ratio. Peaches with high sugar/acid ratio can potentially achieve higher retail values than peaches with low sugar/acid ratio (Minas et al., 2018). Therefore, the application of organic fertilizer increased the yield of peach fruit and improve the quality of peach fruit, which was beneficial to increase the economic income of farmers. Furthermore, with the increase in fertilization levels, the peach fruit yield and sugar/acid ratio also gradually increased, which might be attributed to the improvement of soil nutrients. Similar to commercial organic fertilizer, PBOF can also improve the yield and quality of peach fruit. Importantly, according to government policy, fruit farmers can exchange organic fertilizer through peach branches, which is estimated to be 1.5 tons of organic fertilizer per ton of peach branches, which brings great economic value to fruit farmers and reduces costs.

We further analyzed changes in soil bacterial communities. The application of organic fertilizer (SDH, SKR, and SYT) did not have a significant effect on soil bacterial community diversity compared to CK (Table 3). The Chao1 and Shannon indices also did not change significantly after the application of organic fertilizer in other studies (Jiao et al., 2021; Tan et al., 2023). However, another study showed that organic fertilizer significantly decreased the Chao1 and Shannon indices (Wang T. et al., 2022). Research by Wang et al. (2017) showed that organic fertilizer significantly increased the Chao1 index but had no significant effect on the Shannon index. This may be due to differences in soil and organic fertilizer types. With the exception of SKR.4 and SYT.4 treatments, all fertilization treatments resulted in a decrease in Chao1 and Shannon indices (Table 3). Moreover, the reduction effect of PBOF was more obvious, which might imply a negative impact of PBOF on soil microbial community diversity.

Unlike the results of soil bacterial community diversity, the composition of soil bacterial communities changed significantly after the application of organic fertilizer. At the phylum level, Proteobacteria, Bacteroidetes, Actinobacteria, Gemmatimonadetes, Acidobacteria, and Firmicutes were the dominant bacteria, which were similar to those found in other studies after the application of organic fertilizer (Joa et al., 2014; Chen et al., 2020; Jiao et al., 2021; Wang T. et al., 2022). However, the relative abundance of certain phyla varied among different treatments. For instance, the SKR.4 and SYT.3 treatments significantly increased the relative abundance of Bacteroidetes and Acidobacteria, respectively, but the SDH.4 treatment significantly decreased the relative abundance of Gemmatimonadetes (Supplementary Table S2). At the genus level, SKR.2 treatment significantly increased the relative abundance of Flavobacterium, which is reported to often harbor amylase, cellulase, and chitinase, which are capable of degrading a wide range of organic compounds (Kolton et al., 2016). Furthermore, SDH.4 and SKR.3 treatments significantly increased the relative abundance of Chujaibacter (Figure 2B). Chujaibacter is closely related to heavy metal metabolism (Liang et al., 2021). In another study, Zn application impacted the relative abundance of Ellin6067, a nitrosifying bacterium that converts NH₄⁺ to NO₃⁻, providing an accessible nitrogen source for plants (Lv et al., 2022). Additionally, Dongia has been reported to be responsible for suppressing soil-borne pathogens (Han et al., 2019). In our study, SKR.4 treatment significantly increased the relative abundance of Ellin6067 and Dongia (Figure 2B). Further analyzing the results of LEfSe, we found that Sandaracinus was a biomarker in the SKR.4 treatment (Figure 3). Sandaracinus is a myxobacteria, and a previous study found that the application of organic fertilizer significantly increased the content of soil organic matter, which may promote the growth of myxobacteria (Wang et al., 2020). Interestingly, the soil organic matter content of the SKR.4 treatment was the highest of all the treatments (Table 2). Moreover, Pseudomonas was a biomarker in the SKR.2 treatment (Figure 3). Pseudomonas can restrain the growth of pathogens and degrade pollutants, thereby favoring plant growth (Liu et al., 2020).

These findings highlighted the distinct impacts of different organic fertilizers and fertilization levels on the community composition and abundance of soil bacteria, which might be due to differences in soil chemical properties and the introduction of exogenous microorganisms from organic fertilizers. For the latter, it has been shown that exogenous microbes introduced to the soil from organic fertilizers affect the soil microbial communities. For example, some fungi introduced to the soil from manure were closely related to pathogen-antagonists (Sun et al., 2016). In conclusion, these results indicated that the application of organic fertilizer significantly increased the relative abundance of beneficial bacteria in the soil, which had potential functions in organic compound degradation, heavy metal metabolism, nitrogen supply, and pathogen suppression, thereby promoting soil health and plant growth and revealed that the application of organic fertilizers, including SDH, SKR, and SYT, at different fertilization levels, resulted in significant changes in soil bacterial community.

Many studies have shown a strong correlation between soil chemical properties, soil bacterial communities, and fruit yield and quality (Liu et al., 2020; Wang Z. H. et al., 2022; Zhang et al., 2022b). The same results were found in our correlation analysis, in which many soil bacteria were significantly positively correlated with soil chemical properties and peach yield and quality (Figure 4A). In addition, peach yield and quality were also significantly positively correlated with soil chemical properties (Figure 4B). Nitrogen(N) has a great impact on fruit quality and fruit tree productivity. If N is deficient, the yield will be reduced and the quality of fruits will be poor (Minas et al., 2018). This is consistent with our study that AN was positively correlated with yield and sugar/acid ratio. Moreover, the correlation analysis revealed a positive relationship between AK and both yield and sugar/acid ratio, which same as previous studies showing the beneficial effects of suitable potassium fertilization on internal fruit quality. It can be attributed to the enhancement of photosynthesis rates and the translocation of soluble sugars and organic acids (Minas et al., 2018). These results indicated that the application of organic fertilizers (SDH, SKR, and SYT) promoted peach fruit quality and yield, most likely due to changed soil chemical properties, enhanced soil nutrients, and affected soil bacterial community composition.

The network analysis showed that the response of networks to different organic fertilizers was different for bacterial communities (Figure 5; Supplementary Table S3). Similar results were found in previous studies (Wang et al., 2017; Jin et al., 2022). The decrease in the number of network edges may be due to the increased nutrient supply caused by the application of organic fertilizer, which reduces the difficulty of microorganisms to obtain nutrients and thus the association between microorganisms. In addition, the networks of the two PBOF had a higher ratio of negative links than the network of commercial organic fertilizer. This may be because the introduction of exogenous microorganisms in PBOF has affected the local microbial community (Sun et al., 2020). Moreover, the higher ratio of negative links may be caused by competitive or antagonistic interactions between soil bacteria. This may reduce the invasion of pathogenic microorganisms in the soil and contribute to maintaining the health of the soil ecosystem, and as reported by Li et al. (2019), antagonistic interactions between microorganisms may suppress pathogen invasions. Furthermore, the Kerui PBOF increased the number of positive and negative links of the beneficial bacteria Gemmatimonas and Flavobacterium, compared to the Dahua PBOF, and the network density of the SKR network was the highest among the three networks (Supplementary Tables S3, S4). Overall, the Kerui PBOF may enhance microbial co-occurrence pattern.

The soil bacterial community functions of different treatments were predicted by PICRUSt2. The KEGG results showed that SKR.4 treatment enhanced xenobiotic biodegradation and metabolism and aging (Figure 6B; Supplementary Figure S1). Zhang et al. (2022a) also found the same result after applying organic fertilizer. Further analysis of the level 3 pathways of xenobiotic biodegradation and metabolism and aging revealed that SKR.4 treatment enhanced the metabolism of xenobiotics by cytochrome P450, drug metabolism – cytochrome P450, and longevity regulating pathway – worm (Figure 6B; Supplementary Figure S1). This may indicate that the high-level application of Kerui PBOF influences the degradation and metabolism of exogenous compounds, such as environmental pollutants, through the involvement of cytochrome P450 enzymes. Moreover, the high-level application of Kerui PBOF has the potential to influence the aging of nematodes, which in turn affects bacterial communities and promotes plant growth. In addition, the COG results showed that SKR.4 treatment enhanced cell wall/membrane/envelope biogenesis (Figure 7A). Similar results were found in the study of Ma et al. (2020) and higher available potassium and organic matter content promoted cell wall/membrane/envelope biogenesis. In our study among all fertilization treatments, SKR.4 treatment had the highest SOM and higher AK (Table 2). Further analysis showed that the relative abundance of six COGs in cell wall/membrane/envelope biogenesis increased, suggesting that the high-level application of Kerui PBOF may enhance the composition of the outer membrane of bacteria, which in turn promoted the growth of bacteria (Figure 7B). Overall, these results showed that the application of organic fertilizer affected bacterial community function, especially under the SKR.4 treatment. However, further research is required to fully understand the underlying mechanisms and broader implications of these findings.

This study showed that PBOF could effectively improve the yield and quality of peach fruit and increase soil nutrients. It also changed the soil bacterial community composition and promoted the growth of beneficial bacteria. Moreover, the application of PBOF enhanced the soil bacterial co-occurrence pattern and the potential function of bacterial communities to degrade exogenous compounds. In general, PBOF could achieve similar results to the application effect of commercial organic fertilizer, and the SKR.4 treatment (Kerui PBOF, 5,120 kg/667 m²) was the better choice for the peach orchard in this study. These results will help establish scientific fertilization strategies in peach orchards, ensuring the yield and quality of peach fruit while promoting the sustainable production of peaches. In addition, thanks to the local policy of encouraging the use of PBOF, the use cost of PBOF is lower than commercial organic fertilizer, which is conducive to the development of ecological agriculture.

The data presented in the study are deposited in the NCBI repository, accession number PRJNA937092.

CL and DH developed the concept of this study and are main contributors to writing the manuscript. HY was responsible for performing the field experiments. DH was responsible for performing the lab experiments. CL and ZL performed the data analysis and prepared the figures. CG and YL contributed to the manuscript edit and review. All authors contributed to the article and approved the submitted version.

This study was supported by the Deloitte Charity Foundation – Demonstration of Low-Carbon Circular Agriculture in Pinggu District (202101226).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

The Supplementary material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmicb.2023.1223420/full#supplementary-material