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Article

Improved Straw Decomposition Products Promote Peanut Growth by Changing Soil Chemical Properties and Microbial Diversity

by
Yaxin Liu
1,
Meng Wu
1,2,
Jia Liu
3,
Daming Li
4,
Xiaoli Liu
1,
Ling Chen
1,
Xi Guo
5 and
Ming Liu
1,2,*
1
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Chuangyou Road 298, Nanjing 211135, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
3
National Engineering and Technology Research Center for Red Soil Improvement, Soil and Fertilizer & Resources and Environment Institute, Jiangxi Academy of Agricultural Sciences, Nanchang 330200, China
4
Jiangxi Institute of Red Soil & Germplasm Resource, Nanchang 330029, China
5
Key Laboratory of Arable Land Improvement and Quality Improvement of Jiangxi Province, Nanchang 330045, China
*
Author to whom correspondence should be addressed.
Sustainability 2024, 16(16), 7096; https://doi.org/10.3390/su16167096
Submission received: 2 July 2024 / Revised: 25 July 2024 / Accepted: 1 August 2024 / Published: 19 August 2024
(This article belongs to the Section Sustainable Agriculture)
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Abstract

:
The ameliorative effects of straw decomposition products on soil acidification have been extensively studied. However, the impact of chemically treated straw decomposition products on crop productivity and the underlying microbial mechanisms remain unclear. This study aimed to investigate the effects of two dosages of Ca(OH)2-treated straw decomposition products of peanuts on red soil acidity, fertility, and bacterial and fungal diversity through a pot experiment. The pot experiment included four treatments: chemical nitrogen, phosphorus, and potassium (NPK) fertilization alone (CK), NPK chemical fertilization combined with peanut straw decomposition products (PS), NPK chemical fertilization combined with 4% Ca(OH)2-treated peanut straw decomposition products (PS4Ca), and NPK chemical fertilization combined with 8% Ca(OH)2-treated straw decomposition products (PS8Ca). High-throughput sequencing was performed to investigate the effects of these treatments on soil microbial diversity. The treatments with PS, PS4Ca, and PS8Ca significantly increased soil pH, exchangeable base cations, and nutrient content, whereas they decreased the exchangeable acid, especially exchangeable aluminum. The peanut growth improved substantially with the application of straw decomposition products. Specifically, PS4Ca significantly increased the Shannon and Richness indices of fungi. The principal coordinate analysis showed that the soil microbial communities in the straw decomposition product treatments were significantly different from CK. Linear discriminant analysis effect size identified unique bacteria and fungi between treatments. The Mantel test indicated that exchangeable base cations and pH were significantly positively correlated with bacterial communities, whereas available potassium was positively correlated with fungal communities. The partial least squares path modeling revealed that the bacterial communities positively and directly affected all peanut agronomic traits. In contrast, the fungal communities had a negative and direct effect only on peanut 100-pod weight. Therefore, adding Ca(OH)2-treated straw decomposition products could effectively improve crop productivity by alleviating soil acidification, increasing soil nutrients, and subsequently changing microorganisms.

1. Introduction

Returning straw to fields for decomposition is crucial for improving the ecological environment, boosting soil fertility, maintaining nutrient balance, and enriching organic matter in farmland soil [1,2,3]. The effects of chemical additives on straw decomposition and subsequent soil improvement have also been studied. For example, adding alkali slag or FeSO4 increases the nutrient content and promotes the decomposition of peanut straw. These straw decomposition products also ameliorate soil acidification and improve soil fertility [4]. Incorporating alkaline slag and crop residues was also effective in lowering soil exchangeable acidity and aluminum saturation, enriching exchangeable base cations, and increasing the efficiency of organic N fertilizer utilization [5].
Soil microorganisms are key in nutrient cycling, detoxification processes, and soil aggregate stability in terrestrial ecosystems. The activities of soil microbial communities determine the productivity and overall quality of agroecosystems [6]. The bacterial and fungal communities in soil are sensitive to environmental changes, and their diversity is often seen as an important indicator of soil quality [7]. In recent years, researchers found that straw returning could increase soil microbial diversity, improving crop productivity. For example, Xia et al. studied the effects of different artificial tillage and straw-returning practices on soil microbial communities, thereby enhancing crop yields [8]. However, the straw returning might cause microorganisms to compete with crops for nutrients. Therefore, studying the impact of straw decomposition products on soil microbial diversity is crucial to understand the mechanism underlying crop productivity improvement.
Red soil is the dominant soil type in southern China [9], and its acidification poses significant environmental and ecological problems, affecting food safety [10]. Long-term fertilizer application has led to soil acidification and reduced yields in crops such as wheat and maize [11]. Ameliorating the acidity of red soil is essential for improving crop yields and maintaining soil sustainability. Peanut (Arachis hypogaea L.) is a vital cash crop in China and one of the four major oilseed crops in the red soil region [12]. Increasing peanut yields is important for the development of the Chinese agricultural economy. Due to allelopathy, peanut straw cannot be directly returned to the field. Studies have shown that adding chemical additives can enhance the nutrient content of peanut straw decomposition products (PS), eliminate negative effects, and promote soil microbial function [4]. Among these additives, calcium hydroxide [Ca(OH)2] is commonly used. However, the effects of Ca(OH)2-treated straw decomposition products on soil acidification, microbial communities and diversity, and peanut productivity remain unclear.
Therefore, this study aimed to investigate the effects of two dosages of Ca(OH)2-treated straw decomposition products on red soil acidity, fertility, and bacterial and fungal diversity through a pot experiment. The possible mechanisms behind these effects on peanut growth were also investigated. The study hypothesized that (1) straw decomposition products treated with Ca(OH)2 additives would have a better overall improvement effect than straw decomposition alone, and (2) bacterial and fungal diversities have a distinct impact on crop growth through changes in soil chemical properties.

2. Materials and Methods

2.1. Straw Decomposition Products and Tested Soil

Peanut straw was ground and passed through a 40-mesh sieve, then mixed with either no Ca(OH)2, 4% Ca(OH)2, or 8% Ca(OH)2. A 0.5% EM agent (mainly containing photosynthetic bacteria, yeast, lactic acid bacteria, actinomyces, and bacillus) was added. The carbon-to-nitrogen (C/N) ratio was adjusted to 25 with urea, and the water content was brought to 65% using distilled water. This mixture was then incubated at a constant temperature of 28 °C for 180 days. The 8% chemical additive dosage was based on a previous report [13], with half that amount used for comparison. The properties of the decomposed products are shown in Table S1. The test soil, derived from Quaternary red clay, was sampled from the Ecological Experimental Station of Red Soil Academia Sinica, Yingtan City, Jiangxi Province (28°15′30″ N, 116°55′30″ E). After removing small stones and plant residues, the soil was air-dried, ground, and passed through a 5 mm sieve for the subsequent pot experiment. The properties of the tested soil are listed in Table S2.

2.2. Pot Experiment

Four treatments were conducted: (1) NPK chemical fertilization alone (CK), (2) NPK chemical fertilization combined with PS, (3) NPK chemical fertilization combined with 4% Ca(OH)2-treated straw decomposition products (PS4Ca), and (4) NPK chemical fertilization combined with 8% Ca(OH)2–treated straw decomposition products (PS8Ca). The application rates for the chemicals N, P2O5, and K2O were about 150, 75, and 150 kg ha−1, respectively. The straw decomposition products were applied at 13 g kg−1 for PS, 13.4 g kg−1 for PS4Ca, and 15.2 g kg−1 for PS8Ca, maintaining an equal carbon amount (0.4%) for each pot treatment. Each treatment had three replicates arranged randomly.
In the pot experiment, the Ganhua 1 peanut variety was used. Each pot was filled with 5 kg of air-dried soil. The chemical fertilizers and straw decomposition products were evenly mixed into the soil, and the pots were well-watered uniformly. Three peanut seeds were sown in each pot 1 day later. One peanut seedling with uniform growth was left in each pot after 7 days of seedling emergence. The plant height and chlorophyll content were measured at various stages: seedling, flowering and needling, podding, fruit ripening, and harvest. After harvest, peanut plant biomass, pod biomass, and 100-fruit weight under different treatments were measured, and soil samples under different treatments were collected. Soil samples were air-dried for chemical analysis, and fresh samples were stored at −20 °C for microbial DNA extraction and high-throughput sequencing.

2.3. Soil and Plant Analysis

Soil chemical properties were determined using methods described by Pansu and Gautheyrou [14]. The soil pH was measured with a pH meter (FE30; Mettler-Toledo; Shanghai) using a water–soil ratio of 2.5:1. The soil organic carbon (SOC) content was determined using potassium dichromate oxidation with external heating. The total nitrogen (TN) content was determined using the Kjeldahl method. The available nitrogen (AN) content was determined using the alkali hydrolysis and micro-diffusion methods. The total phosphorus (TP) and available phosphorus (AP) contents were determined using the vanadium–molybdate photometric method. The total potassium (TK) and available potassium (AK) contents were determined by inductively coupled plasma-atomic emission spectrometry. The basic properties of the soil are listed in Table S1.
Post-harvest, plant samples were first baked at 105 °C for 30 min, then at 80 °C until a constant mass was reached. Then, the dry mass of plant biomass, pod weight, and 100-fruit weight were measured.

2.4. Soil DNA Extraction and High-Throughput Sequencing

A fast DNA spin kit (MP Biomedicals, Irvine, CA, USA) was used to extract the soil total microbial genomic DNA from 0.5 g fresh soil. Then, the extracted total DNA was purified by a Power Clean DNA Clean-up Kit (Mobio, Carlsbad, CA, USA). The concentration and quality (OD260/OD280) of the extracted DNA were detected using the NanoDrop ND-1000 spectrophotometer (NanoDrop Technologies, Wilmington, DE, USA). For bacterial analysis, the V4-V5 region of the 16S rRNA gene was amplified using the universal primers 515F (5′-GTGCCAGCMGCCGCGGTAA-3′) and 907R (5′-CCGTCAATTCCTTTGAGTTT-3′) [15]. For fungal analysis, the ITS1 region was amplified using the universal primers ITS1 (5′-GGAAGTAAAAGTCGTAACAAGG-3′) and ITS5F (5′-GCTGCGTTCTTCATCGATGC-3′) [16]. The PCR protocol for the 16S region involved an initial denaturation at 95 °C for 3 min, followed by 27 cycles at 95 °C for 30 s, annealing at 55 °C for 30 s, extension at 72 °C for 45 s, and extension at 72 °C for 10 min. For the ITS region, the protocol included an initial denaturation at 95 °C for 3 min, followed by 35 cycles at 95 °C for 30 s, annealing at 55 °C for 30 s, extension at 72 °C for 45 s, and finally extension at 72 °C for 10 min. The amplified products were sequenced using the Illumina Miseq sequencing platform (Shanghai Genesky Biotechnologies Inc., Shanghai, China).
Raw sequence data were processed in the QIIME2 environment (release 2021.8), using the DADA2 pipeline for denoising [17]. The remaining quality-filtered reads were assembled into error-corrected amplicon sequence variants (ASVs) at 100% sequence identity, representing unique microbial taxa. Representative sequences of bacterial and fungal ASVs were aligned against the SILVA 138 database and the UNITE reference database using an open-reference Naïve Bayes feature classifier, respectively.

2.5. Data Analysis

SPSS and Prism were used for data processing, statistical analysis, and visualization. Significant differences in soil chemical and microbial properties, as well as peanut agronomic traits between treatments, were calculated using one-way analysis of variance with Duncan’s test at a significance level of p < 0.05. The QIIME2 was used for calculating microbial α diversity indices. The principal coordinate analysis (PCoA) was conducted based on the Bray–Curtis distance using the vegan package (R version 4.1.2). The Mantel test, also using the vegan package (R version 4.1.2), was conducted to analyze the correlation between soil microbial communities and soil chemical factors. The linear discriminant analysis effect size (LEfSe) method, implemented in the microeco package (R version 4.1.2), was used to identify potential microbial markers for different straw decomposition product treatments. The partial least squares path modeling (PLS-PM) was used to analyze the comprehensive effects of soil chemical properties and microbial community on the agronomic traits of soil peanuts.

3. Results

3.1. Effect of Ca(OH)2-Treated Straw Decomposition Products on Soil Chemical Properties

Compared with the application of chemical fertilizer alone, the treatments of PS, PS4Ca, and PS8Ca increased soil pH and improved soil fertility. The soil pH increased by 1.15, 1.95, and 1.78 units under these three treatments, respectively. The SOC content increased by 24.9%, 21.1%, and 15.0%, the TN content by 30.9%, 26.8%, and 23.7%, the TP content by 9.1%, 6.1%, and 23.7%, and the total potassium by 2.1%, 0.98%, and 4.0%, respectively. Regarding soil available nutrients, compared with CK, the AN content increased by 37.3%, 23.0%, and 19.7% under the PS, PS4Ca, and PS8Ca treatments, respectively. Similarly, the AP content increased by 2.6%, 18.2%, and 14.3%, and the available potassium content increased by 61.9%, 48.8%, and 45.2%, respectively (Table S3).
Compared with CK, the exchangeable acid in the PS, PS4Ca, and PS8Ca treatments decreased by 78.3%, 100%, and 100%, respectively, whereas the exchangeable base cations increased by 66.1%, 144.8%, and 145.9%, respectively (Figure 1).

3.2. Effect of Ca(OH)2-Treated Straw Decomposition Products on Peanut Growth

Throughout the peanut growth period, the height of the plants treated with PS4Ca increased by 95.6–125.3% compared with that of the CK. Additionally, the chlorophyll content in their leaves was 51.0–173.1% higher than that of the CK (Figure 2). Compared with the single application of chemical fertilizers, the PS4Ca treatment resulted in a 2.47-, 1.87-, and 1.39-fold increase in peanut plant biomass, peanut pod biomass, and 100-pod weight after harvest, respectively (Figure 3).

3.3. Effect of Ca(OH)2-Treated Straw Decomposition Products on Soil Microbial Diversity

The bacterial Shannon and Richness indices were higher in the PS and PS4Ca treatments than those in the CK. The indices were lower in the PS8Ca treatment than in the CK. However, the differences in bacterial α diversity between treatments were not significant (Figure 4a,c). The fungal Shannon and Richness indices were significantly higher in the PS4Ca treatment than in the CK. However, these fungal diversity indices were significantly lower in the PS8Ca treatment (Figure 4b,d).
The principal coordinate analysis (PCoA) was used to compare soil microbial community differences among the four treatments. The PCoA axes 1 and 2 explained 56.00% and 11.78% of the variation in bacterial communities, respectively (Figure 5a). For fungal communities, PCoA axes 1 and 2 explained 55.45% and 22.24% of the variation, respectively (Figure 5b). The results indicated a clear differentiation in soil bacterial and fungal communities among treatments.
Treatment with PS4Ca increased the relative abundance of bacterial phyla Pseudomonadota, Bacillota, Bacteroidetes, and Thermodesulfobacteriota, while decreasing the relative abundance of Caldatribacteriota, Crenarchaeota, and Actinomycetota (Figure 6a). Ascomycota was the predominant fungal phylum across treatments, constituting more than 80% of the total taxonomic phylum. PS4Ca treatment increased the relative abundances of Ascomycota and Basidiomycota, but decreased those of Mucoromycota and Mortierellomycotina (Figure 6b).
LEfSe analysis identified unique microbial biomarkers between treatments (Figure 7). For bacteria, Caldatribacteriota was significantly enriched in CK, whereas Parcubacteria belonging to Patescibacteria was significantly enriched in the PS4Ca treatment, and Bacillota in the PS8Ca treatment (Figure 7a). For fungi, the tongaense (species) of Hypocreales was significantly enriched in CK, whereas the Equi (species) of Sordariales and Fusarium were significantly enriched in PS. The Rileyi (species) and mucidum (species) of Hypocreales were significantly enriched in PS4Ca, and the Condenascus (genus) of Sordariales and Fusarium in PS8Ca (Figure 7b).

3.4. Relationships between Soil Chemical Properties, Microbial Diversity, and Peanut Growth

Mantel’s test analyses revealed that exchangeable base cations, exchangeable acid, pH, SOC, TN, AN, AP, and AK were significantly positively correlated with bacterial communities (p < 0.01). However, TP and TK did not show a significant correlation with bacterial communities (Figure 8). All 10 soil chemical properties were positively correlated with fungal communities (p < 0.05) (Figure 8).
The PLS-PM was used to clarify the direct and indirect relationships between soil chemical properties, microbial communities, and peanut agronomic traits (Figure 9). The results indicated that soil chemical properties directly affected peanut plant biomass (coefficient 0.530, p < 0.01) and the weight of 100 pods (coefficient 0.947, p < 0.05). Soil chemical properties also significantly influenced bacterial communities (coefficient 0.666, p < 0.05), indirectly affecting the peanut plant biomass (coefficient 0.701, p < 0.01), pod biomass (coefficient 1.35, p < 0.01), and weight of 100 pods (coefficient 1.25, p < 0.05). Additionally, soil chemical properties had a positive correlation with fungal communities (coefficient 0.820, p < 0.001), which indirectly affected the weight of 100 pods (coefficient −1.403, p < 0.001).

4. Discussion

4.1. Beneficial Effects of Ca(OH)2-Treated Straw Decomposition Products on Soil Acidification, Soil Fertility, and Peanut Growth

Compared with CK, treatments with PS, PS4Ca, and PS8Ca significantly increased soil pH. The straw decomposition products, especially those treated with chemical additives, were alkaline (Table S1). This was one of the reasons for the increasing pH of red soil after applying the straw decomposition products (Table S1). Additionally, the presence of abundant organic functional groups in the straw decomposition products further enhanced the soil pH through organic anionic linkage and subsequent decarboxylation processes [18]. The combination of chemical fertilization and the application of Ca(OH)2-treated straw decomposition products significantly decreased soil exchangeable acidity and aluminum. This was because exchangeable Al3+ in the soil transformed into hydroxyl-aluminum via polymerization and hydrolysis reactions, leading to the precipitation of aluminum hydroxides and reducing exchangeable Al3+ [19,20]. Compared with CK, the exchangeable base cations in the soil treated with PS, PS4Ca, and PS8Ca increased significantly, likely due to the release of abundant Ca and Mg during straw decomposition [20,21]. After applying the straw decomposition products to the soil, the cations Ca and Mg were absorbed by the soil and converted into an exchangeable base.
The addition of straw decomposition products also increased SOC, TN, TP, TK, AN, AP, and AK, aligning with previous findings [22]. Generally, applying organic matter to the soil increases the soil organic matter and nutrient content. For example, composting has been shown to increase soil organic matter [23,24] and mineral nutrients such as N, P, and K [25].
Plants treated with straw decomposition products exhibited a significant increase in height and leaf chlorophyll content during the growth period. At harvest, plant biomass, pod biomass, and 100-fruit weight were significantly higher, consistent with previous studies [26]. First, the application of straw decomposition products increased the soil pH and improved the growing environment of the crop, thus promoting crop growth [20]. This study showed that the exchangeable base cation content was significantly elevated and soil exchangeable Al3+ was reduced in treatments with straw decomposition compared with the CK. This indicated that the toxic effects of aluminum activity on the peanut root system were effectively reduced. Second, in this study, the nutrients from the straw decomposition products were beneficial to crop growth [21], as evidenced by higher levels of TN, TP, AN, AP, and AK in the treated soil compared with CK. Therefore, the straw decomposition products increased the soil nutrient content and improved crop growth [20]. Finally, the microbial community might have changed due to the application of straw decomposition products, further promoting plant growth [27].

4.2. Impact of Ca(OH)2-Treated Straw Decomposition Products on Bacterial and Fungal Diversity

Soil microbial diversity is crucial for maintaining the soil quality, productivity, and ecological balance in agroecosystems [28]. The organic matter, such as compost, significantly increased soil microbial diversity in potato production [29]. The application of chemical amendments not only promoted the straw decomposition products but also increased both the microbial biomass and functional diversity in the soil [4]. In this study, bacterial diversity was not significantly affected by PS, probably due to higher bacterial diversity at a neutral pH than in alkaline or acidic soils [30]. However, fungal diversity was significantly influenced by 4% Ca(OH)2-treated straw decomposition products. Fungi are more sensitive to external disturbances than bacteria. Previous studies have shown that straw return provided organic carbon sources and nutrients for fungi, increasing soil fungal diversity [31].
The PCoA analysis results indicated that the microbial community composition of soils treated with the straw decomposition products differed significantly from CK. Previous studies have shown that applying bio-compost altered the community structure of soil microbial communities [32]. The application of straw decomposition products in this study alleviated soil nutrient limitations and affected the growth of different trophic microorganisms. For example, the abundance of eutrophic microorganisms, Pseudomonadota and Ascomycota, increased, and the abundance of oligo-trophic microorganisms, Actinomycetota and Mucoromycota, decreased. The specific functional microorganisms in the exogenous straw decomposition products also interacted with native soil microorganisms, altering the microbial community structure [32].
LEfSe analyses revealed changes in the dominant bacteria and fungi induced by straw decomposition products. For bacteria, Caldatribacteriota was enriched in CK in this study, likely due to its adaptation to low organic carbon and energy availability [33]. Parcubacteria belonging to Patescibacteria were most abundant in PS4Ca. A previous study showed that long-term nitrogen application increased Patescibacteria abundance by altering soil pH, and Patescibacteria showed significant positive correlations with crop yield [34]. Thus, we assumed that enriching Parcubacteria in PS4Ca could improve peanut growth. The Bacillota species were most abundant in PS8Ca, possibly due to higher K+ content. Zhao et al. reported that K+ ions were key in promoting Bacillota growth [35]. For fungi, Rileyi (species) and Mucidum (species) belonging to Hypocreales were most abundant in PS4Ca, possibly due to their versatility and ability to use a wide range of carbon sources, and are considered as efficient cellulolytic fungi [36]. Previous studies have indicated that a higher pH positively affects the abundance of Hypocreales, consistent with the findings of this study [37]. In this study, PS4Ca improved soil chemical properties and increased soil pH. However, the tongaense (species) belonging to Hypocreales was dominant in CK. This suggested that different fungal species within the same order may respond differently to various factors. The Sordariales (order) was the most abundant in PS and PS8Ca treatments. The higher abundance of Sordariales in the PS treatment may be attributed to the increased TN and SOC [38]. In the PS8Ca treatment, the higher abundance of Sordariales could be due to increased AP [39]. Additionally, the Fusarium species was significantly more prevalent in the PS and PS8Ca treatments, indicating an accumulation of pathogenic fungi.

4.3. Potential Effects of Ca(OH)2-Treated Straw Decomposition Products on Peanut Growth

Studies confirmed that soil physical and chemical factors could drive changes in soil bacterial and fungal community composition [40]. The Mantel test showed that exchangeable base cations and pH were significantly positively correlated with bacterial communities, whereas the AK was positively correlated with fungal communities. Many soil properties (such as SOC, TN, TP, AP, and AK) influenced both soil bacterial and fungal communities, consistent with previous studies [41,42], indicating that soil microbial community diversity depended on soil nutrient supply [43]. Exchangeable base cations, including K+, Na+, Ca2+, and Mg2+, were also major environmental variables controlling these bacterial and fungal communities [44].
The PLS-PM results showed that soil chemical properties could significantly improve peanut agronomic traits. These properties also indirectly influenced the peanut agronomic traits through their impact on bacterial and fungal communities. Interestingly, the bacterial community had a positive direct effect on all peanut agronomic traits. In contrast, the fungal community only had a negative direct effect on the weight of 100 pods (Figure 9). This finding was consistent with previous studies suggesting that soil bacteria, rather than fungi, are key factors reflecting changes in plant characteristics [45]. The relatively stable bacterial diversity across different treatments indicated that bacterial function in this study was crucial for peanut growth. The negative impact of fungi on peanut growth may be due to the accumulation of pathogenic fungi. For example, Fusarium was significantly enriched in the PS and PS8Ca treatments, and previous studies showed that peanut root rot caused by Fusarium was a primary reason for reduced yield and poor growth in red soil monocultures [46]. This explained why the PS and PS8Ca treatments were less effective in promoting peanut growth.

5. Conclusions

The results showed that Ca(OH)2-treated straw decomposition products could improve soil chemical properties and hence the agronomic traits of peanuts. Treatments with PS, PS4Ca, and PS8Ca significantly increased soil pH, exchangeable base cations, and nutrient content, while decreasing exchangeable acidity. The improved soil chemical properties indirectly influenced peanut agronomic traits through changes in bacterial and fungal communities. The Mantel test revealed that exchangeable base cations and pH were significantly positively correlated with bacterial communities, whereas AK was positively correlated with fungal communities. The PLS-PM results indicated that bacterial communities had a positive direct effect on all peanut agronomic traits. In contrast, fungal communities had a negative direct effect only on the weight of 100 pods. The straw decomposition increased fungal diversity and altered community structure, which had a direct negative impact on peanut agronomic traits.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/su16167096/s1, Table S1. Properties of the decomposed products; Table S2. Basic properties of the tested soil; Table S3. Soil chemical properties under different treatments.

Author Contributions

Methodology, M.W., J.L., D.L., X.L., L.C., X.G. and M.L.; Writing—original draft, Y.L.; Writing—review & editing, M.L.; Funding acquisition, M.L. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Key Research and Development Program of China (2021YFD1901201, 2022YFD1900603), the National Natural Science Foundation of China (42167049), the Key Research and Development Program of Jiangxi Province (20212BBF63007), the Jinggangshan Agricultural Hi-tech District Project (20222-051261).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Soil exchangeable acid content (a) and exchangeable base cation content (b) under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. Lowercase letters above the columns indicate a significant difference at p < 0.05.
Figure 1. Soil exchangeable acid content (a) and exchangeable base cation content (b) under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. Lowercase letters above the columns indicate a significant difference at p < 0.05.
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Figure 2. Peanut plant height (a) and leaf chlorophyll content (b) during the reproductive period of peanuts. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. The Arabic numerals on the axis x represent different growth periods—1: seedling stage, 2: flowering and needling stage, 3: podding stage, 4: fruit ripening stage, and 5: harvest stage, respectively.
Figure 2. Peanut plant height (a) and leaf chlorophyll content (b) during the reproductive period of peanuts. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. The Arabic numerals on the axis x represent different growth periods—1: seedling stage, 2: flowering and needling stage, 3: podding stage, 4: fruit ripening stage, and 5: harvest stage, respectively.
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Figure 3. Peanut plant biomass (a), peanut pod biomass (b), and peanut 100-fruit weight (c) under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. Lowercase letters above the columns indicate a significant difference at p < 0.05.
Figure 3. Peanut plant biomass (a), peanut pod biomass (b), and peanut 100-fruit weight (c) under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. Lowercase letters above the columns indicate a significant difference at p < 0.05.
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Figure 4. Soil bacterial Shannon indices (a) and Richness indices (c) and fugal Shannon indices (b) and Richness indices (d) under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. Lowercase letters above the boxes indicate a significant difference at p < 0.05.
Figure 4. Soil bacterial Shannon indices (a) and Richness indices (c) and fugal Shannon indices (b) and Richness indices (d) under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. Lowercase letters above the boxes indicate a significant difference at p < 0.05.
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Figure 5. Principal coordinate analysis (PCoA) of the bacterial (a) and fungal (b) community composition under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. Different color symbols represent different treatments.
Figure 5. Principal coordinate analysis (PCoA) of the bacterial (a) and fungal (b) community composition under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2. Different color symbols represent different treatments.
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Figure 6. Relative bacterial (a) and fungal (b) phylum abundance under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2.
Figure 6. Relative bacterial (a) and fungal (b) phylum abundance under different treatments. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2.
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Figure 7. LEfSe analysis of bacterial (a) and fungal (b) communities under different treatments (p < 0.05, LDA score ≥ 3). Circles from inside to outside indicate the phylogenetic level of bacteria and fungi from domain to species. Prefixes of each bacterial and fungal taxonomic name such as p, c, o, f, g, and s are the initial letters of phylum, class, order, family, and genus, and species respectively. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2.
Figure 7. LEfSe analysis of bacterial (a) and fungal (b) communities under different treatments (p < 0.05, LDA score ≥ 3). Circles from inside to outside indicate the phylogenetic level of bacteria and fungi from domain to species. Prefixes of each bacterial and fungal taxonomic name such as p, c, o, f, g, and s are the initial letters of phylum, class, order, family, and genus, and species respectively. CK: chemical fertilization, PS: chemical fertilization combined with the application of peanut straw decomposition, PS4Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 4% Ca(OH)2, PS8Ca: chemical fertilization combined with the application of peanut straw decomposition products treated by 8% Ca(OH)2.
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Figure 8. The Mantel test between soil chemical properties and microbial communities. SOC: soil organic carbon, TN: soil total nitrogen, TP: soil total phosphorous, TK: soil total potassium, AN: soil available nitrogen, AP: soil available phosphorus, AK: soil available potassium, exchangeable acid: exchangeable H+ and exchangeable 1 3 Al3+, exchangeable base cations: exchangeable K++ Na+ + 1 2 Mg2+ and exchangeable 1 2 Ca2+. Red line represents p < 0.01; green line represents 0.01< p < 0.05; gray line represents p > 0.05. Asterisks (*) indicate levels of statistical significance: * p < 0.05, ** p < 0.01, *** p < 0.001.
Figure 8. The Mantel test between soil chemical properties and microbial communities. SOC: soil organic carbon, TN: soil total nitrogen, TP: soil total phosphorous, TK: soil total potassium, AN: soil available nitrogen, AP: soil available phosphorus, AK: soil available potassium, exchangeable acid: exchangeable H+ and exchangeable 1 3 Al3+, exchangeable base cations: exchangeable K++ Na+ + 1 2 Mg2+ and exchangeable 1 2 Ca2+. Red line represents p < 0.01; green line represents 0.01< p < 0.05; gray line represents p > 0.05. Asterisks (*) indicate levels of statistical significance: * p < 0.05, ** p < 0.01, *** p < 0.001.
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Figure 9. Partial least squares path model for the effect of soil chemical properties and microbial communities on peanut agronomic traits. Positive effects are indicated by red lines and negative effects are indicated by blue lines. The arrowheads indicate the hypothesized direction of causality. Asterisks (*) indicate levels of statistical significance: * p < 0.05, ** p < 0.01, *** p < 0.001.
Figure 9. Partial least squares path model for the effect of soil chemical properties and microbial communities on peanut agronomic traits. Positive effects are indicated by red lines and negative effects are indicated by blue lines. The arrowheads indicate the hypothesized direction of causality. Asterisks (*) indicate levels of statistical significance: * p < 0.05, ** p < 0.01, *** p < 0.001.
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Liu, Y.; Wu, M.; Liu, J.; Li, D.; Liu, X.; Chen, L.; Guo, X.; Liu, M. Improved Straw Decomposition Products Promote Peanut Growth by Changing Soil Chemical Properties and Microbial Diversity. Sustainability 2024, 16, 7096. https://doi.org/10.3390/su16167096

AMA Style

Liu Y, Wu M, Liu J, Li D, Liu X, Chen L, Guo X, Liu M. Improved Straw Decomposition Products Promote Peanut Growth by Changing Soil Chemical Properties and Microbial Diversity. Sustainability. 2024; 16(16):7096. https://doi.org/10.3390/su16167096

Chicago/Turabian Style

Liu, Yaxin, Meng Wu, Jia Liu, Daming Li, Xiaoli Liu, Ling Chen, Xi Guo, and Ming Liu. 2024. "Improved Straw Decomposition Products Promote Peanut Growth by Changing Soil Chemical Properties and Microbial Diversity" Sustainability 16, no. 16: 7096. https://doi.org/10.3390/su16167096

APA Style

Liu, Y., Wu, M., Liu, J., Li, D., Liu, X., Chen, L., Guo, X., & Liu, M. (2024). Improved Straw Decomposition Products Promote Peanut Growth by Changing Soil Chemical Properties and Microbial Diversity. Sustainability, 16(16), 7096. https://doi.org/10.3390/su16167096

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