Peanut-based intercropping systems altered soil bacterial communities, potential functions, and crop yield.

Intercropping is an efficient land use and sustainable agricultural practice widely adopted worldwide. However, how intercropping influences the structure and function of soil bacterial communities is not fully understood. Here, the effects of five cropping systems (sole sorghum, sole millet, sole peanut, sorghum/peanut intercropping, and millet/peanut intercropping) on soil bacterial community structure and function were investigated using Illumina MiSeq sequencing. The results showed that integrating peanut into intercropping systems increased soil available nitrogen (AN) and total nitrogen (TN) content. The alpha diversity index, including Shannon and Chao1 indices, did not differ between the five cropping systems. Non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) illustrated a distinct separation in soil microbial communities among five cropping systems. Bacterial phyla, including Actinobacteria, Proteobacteria, Acidobacteria, and Chloroflexi, were dominant across all cropping systems. Sorghum/peanut intercropping enhanced the relative abundance of phyla Actinobacteriota and Chloroflexi compared to the corresponding monocultures. Millet/peanut intercropping increased the relative abundance of Proteobacteria, Acidobacteriota, and Nitrospirota. The redundancy analysis (RDA) indicated that bacterial community structures were primarily shaped by soil organic carbon (SOC). The land equivalent ratio (LER) values for the two intercropping systems were all greater than one. Partial least squares path modeling analysis (PLS-PM) showed that soil bacterial community had a direct effect on yield and indirectly affected yield by altering soil properties. Our findings demonstrated that different intercropping systems formed different bacterial community structures despite sharing the same climate, reflecting changes in soil ecosystems caused by interspecific interactions. These results will provide a theoretical basis for understanding the microbial communities of peanut-based intercropping and guide agricultural practice.

Organ removal of maize increases peanut canopy photosynthetic capacity, dry matter accumulation, and yield in maize/peanut intercropping.

In maize/peanut intercropping systems, shade from maize is a major factor in peanut yield reduction. Reasonable redundant organ removal of maize plants could alleviate this problem and improve intercropped peanut yields. We studied the influences of organ removal of maize on peanut canopy photosynthetic capacity, dry matter accumulation and yield in maize/peanut intercropping systems in 2021 and 2022. Five organ-removal treatments were performed on maize plants to ameliorate the light environments in the peanut canopy. Treatments consisted of removal of the tassel only (T1), the tassel with top two leaves (T2), the tassel with top four leaves (T3), the tassel with top six leaves (T4), the leaves below the second leaf below the ear (T5), with no removal as control (T0). The results showed that organ-removal treatment (T4) significantly improved the photosynthetically active radiation (PAR, 49.5%) of intercropped peanut canopy. It improved dry matter accumulation by increasing the canopy photosynthetic capacity (canopy apparent photosynthetic rate (CAP), leaf area index (LAI), and specific leaf area (SLA)), ultimately contributing to peanut yield by increasing pod number per plant. Also, the above results were verified by structural equation modeling. The yield of intercropped peanut reached the highest value at T4. At the level of intercropping systems, the land equivalent ratio (LER) peaked at T2 (1.56, averaged over the two years), suggesting that peanut and maize can coexist more harmoniously under T2 treatment. The T2 treatment increased peanut yield by an average of 7.1% over two years and increased maize yield by 4.7% compared to the T0 treatment. The present study suggests that this may be an effective cultivation measure to mitigate intercropping shade stress in terms of adaptive changes in intercropped peanut under maize organ removal conditions, providing a theoretical basis for intercropped peanut yield increase.

[Soil Bacterial Community Structure and Function Prediction of Millet/Peanut Intercropping Farmland in the Lower Yellow River].

The objective of this study was to explore the microecological variability in farmland soil fertility in response to millet-peanut intercropping patterns by clarifying the effects of millet-peanut 4:4 intercropping on soil bacterial community structure and its diversity, as well as to provide a reference basis for promoting ecological restoration and arable land quality improvement in the lower Yellow River farmland. The Illumina MiSeq high-throughput sequencing technology and QIIME 2 platform were used to analyze the differences in bacterial community composition and their influencing factors in five soils[sole millet (SM), sole peanut (SP), intercropping millet (IM), intercropping peanut (IP), and millet-peanut intercropping (MP)] and to predict their ecological functions. The results showed that the α-diversity of intercropping soil bacterial communities differed from that of monocropping, though not significantly, whereas the ß-diversity was significantly different (P<0.05). A total of 7081 ASVs were obtained from all soil samples, classified into 34 phyla, 109 orders, 256 class, 396 families, 710 genera, and 1409 species, of which 727 ASVs were shared, accounting for 24.5% to 27.8% in five soil species. The bacterial communities of millet-peanut intercropping and its monocropping soils were similar in phylum composition but varied in relative abundance. All five soils were dominated by the Actinobacteria, Proteobacteria, Acidobacteria, and Chloroflexi, with a relative abundance of 79.40%-81.33%. Soil organic carbon and alkaline nitrogen were the most important factors causing differences in the structures of the five soil bacterial communities at the phylum and genus levels, respectively. The PICRUSt functional prediction revealed that the relative abundance of primary functional metabolism was the largest (78.9%-79.3%), and the relative abundance of secondary functional exogenous biodegradation and metabolism fluctuated the most (CV=3.782%). In terms of the BugBase phenotype, the relative abundance of oxidative stress-tolerant bacteria increased in intercropping millet or peanut soils compared to that in the corresponding monocultures and significantly increased in intercropping millet soils compared to that in sole millet (P<0.05). Oxidative stress-tolerant, Gram-positive, and aerobic phenotypes were highly significantly positively correlated with each other (P<0.01), and all three showed highly significant negative correlations with potential pathogenicity and Gram-negative and anaerobic phenotypes (P<0.01). This showed that millet-peanut intercropping resulted in differences in soil bacterial community diversity, abundance, and metabolic functions and the possibility of reducing the occurrence of potential soil diseases. It can be used to regulate the soil microbiological environment to promote ecological restoration and sustainable development of farmland in the lower Yellow River.

[Structure and Function of Soil Fungal Community in Rotation Fallow Farmland in Alluvial Plain of Lower Yellow River].

This study was conducted to clarify the structure and function of the fungal community and the microecology change characteristics of farmland soil fertility response to different fallow rotation patterns. It aimed to provide a reference for promoting farmland ecological restoration and farmland quality improvement in the alluvial plain of the lower Yellow River. Farmland soil subject to a long-term rotation fallow experiment since 2018 was studied using Illumina MiSeq high-throughput sequencing technology, and the 'FUNGuild' fungal function prediction tool was used to analyze differences in soil fungal community structure and function under the following four rotation fallow regimes: long fallow (LF), winter wheat and summer fallow (WF), winter fallow and summer maize (FM), and annual rotation of winter wheat and summer maize (WM). The results showed that LF (fallow lasting two years) increased the richness and diversity of fungal communities in the topsoil (0-20 cm layer), whereas WF increased the richness and diversity of fungi in the deep soil (20-40 cm layer) after winter wheat harvest. A total of 2262 OTU were obtained from all soil samples, which were divided into 14 phyla, 34 classes, 75 orders, 169 families, 309 genera, and 523 species. OTU shared by the two soil layers included 420 types (0-20 cm layer) and 253 types (20-40 cm layer), respectively. The fungal community structure of the four rotation fallow soils was similar at the phylum level, mainly including Ascomycota, Basidiomycota, and Mortierellomycota. The total abundances of the three dominant bacteria were 91.69%-96.91% (0-20 cm layer) and 91.67%-94.86% (20-40 cm layer), respectively. Principal component analysis showed that the first principal component (PC1) and the second principal component (PC2) could explain the difference in community structure by 45.56% (0-20 cm layer) and 46.20% (20-40 cm layer). Additionally, the LDA results of LEfSe (threshold was 4.0) showed that there were 64 fungal evolutionary branches in LF, FM, WF, and WM with statistically significant differences (P<0.05). According to RDA analysis, total organic carbon (TOC), total phosphorus (TP), available nitrogen (AN), and soil water content (SWC) were the main environmental factors that significantly affected fungal community in the 0-40 cm soil layer (P<0.05). The functional prediction with FUNGuild showed that the main nutrient types among different treatments in different soil layers were saprotrophic, saprotrophic-symbiotrophic, pathotrophic-saprotrophic-symbiotrophic, and pathotrophic. In LF, the nutrient type of topsoil was mainly pathotrophic-saprotrophic-symbiotrophic, whereas in deep soil, the relative abundance of pathotrophic fungi was the highest. Additionally, in the treatments with planted wheat or corn (FM, WF, and WM), saprotrophic was the main type in both soil layers. Therefore, different fallow patterns were linked to variation in the structure, diversity, and nutrient types of soil fungal communities. Based on these results, seasonal fallow practices could regulate the farmland soil micro-ecological environment of intensive planting and promote the health and harmony of farmland soil ecosystems.

[Characteristics of Bacterial Community Structure in Fluvo-aquic Soil Under Different Rotation Fallow].

The aim of this study was to provide a reference for promoting ecological restoration of farmland and the green development of agriculture in the alluvial plain of the lower Yellow River by determining the effects of different rotation fallow patterns on the bacterial community of the fluvo-aquic soil. Farmland soil subject to a long-term rotation fallow experiment since 2018 was studied using Illumina MiSeq high-throughput sequencing technology, and the 'Tax4Fun' bacterial function prediction tool was used to analyze differences in soil bacterial community structure and function under the following four rotation fallow regimes:long fallow(LF), winter wheat and summer fallow(WF), winter fallow and summer maize(FM), and annual rotation of winter wheat and summer maize(WM). The environmental factors affecting changes in the soil bacterial community structure and function were also analyzed. In total, 44 phyla, 146 classes, 338 orders, 530 families, 965 genera, and 2073 species of bacteria were detected in the soil samples from the different rotation fallow regimes, and the dominant bacterial groups were Actinobacteria, Proteobacteria, Acidobacteria, and Chloroflexi in 0-20 cm and 20-40 cm soil layers. However, the relative abundances of the dominant bacteria groups were varied between the rotation fallow regimes. In the 0-20 cm layer of the seasonal fallow soils(WF and FM), bacteria were more abundant and community diversity was higher than that of the WM and LF soils. In 20-40 cm soil layer, the WF soil was more abundant in bacterial and the community was more diverse. Based on the prediction function of the 'Tax4Fun' tool, six primary metabolic pathways, 40 secondary metabolic pathways(18 types with relative abundance greater than 1%), and 264 tertiary metabolic pathways were identified in the soil bacteria of the different rotation fallow regimes. Seasonal fallow(WF and FM) was found to increase the relative abundance of beneficial bacterial metabolic pathways involved in metabolism, environmental information processing, and genetic information processing. According to RDA analysis, the soil bacterial community in the 0-20 cm soil layer was significantly affected by soil moisture, total phosphorus, available phosphorus, available potassium, pH, and C/N ratio(P<0.05), and the soil bacterial community in 20-40 cm soil layer was significantly affected by soil total phosphorus and available phosphorus(P<0.05). Therefore, different fallow patterns were linked to variation in the structure, diversity, and metabolic functions of soil bacterial communities. Based on these results, seasonal fallow practices could promote the health and stability of farmland soil ecosystems.