Continuous Cropping Changes the Composition and Diversity of Bacterial Communities: A Meta-Analysis in Nine Different Fields with Different Plant Cultivation

Chinese goldthread (Coptis chinensis Franch.) represents one of the most important medicinal plants with diverse medicinal applications, but it easily suffers from continuous cropping obstacles in the plantation. In this study, we have selected eight different continuously cropped fields with C. chinensis and fallow field, providing detailed information regarding the diversity and composition of the rhizospheric bacterial communities. We have found a significant difference between fallow field (LH) and other continuously cropped fields in soil pH; the total content of nitrogen, phosphorus, and potassium; and soil enzyme activities. The results indicate that continuous cropping had a significant effect on soil physicochemical properties and enzyme activities under different plant cultivations. The relative abundance of bacterial phyla was significantly altered among the fields; for example, proteobacteria and Actinobacteria were observed to be higher in continuous cropping of maize (HY6) and lower in sweet potato continuous cropping (HH). Alpha diversity analysis showed that different plants with different years of continuous cropping could change the diversity of bacterial communities, among which the effect of maize and Polygonum multiflorum continuous cropping were most significant. Principle coordinate analysis (PCoA) showed that continuously cropped C. chinensis (LZ) and cabbage continuously cropped for 2 years (HS) were slightly clustered together and separated from LH and others. The results showed that the similarity of the bacterial community in the same crop rotation was higher, which further indicated that the bacterial community structure was significantly altered by the continuous cropping system and plant species. Our study provides a foundation for future agricultural research to improve microbial activity and increase crops/cash-crops productivity under a continuous cropping system and mitigate continuous cropping obstacles.

Decoupling of P from C, N, and K Elements in Cucumber Leaves Caused by Nutrient Imbalance under a Greenhouse Continuous Cropping System

There is insufficient information regarding the stoichiometric variation and coupling status of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) in the leaves of nutrient-enriched greenhouse agroecosystems with increasing planting time. Therefore, we assessed the variation in elemental stoichiometry ratios in soil and cucumber (Cucumis sativus L.) leaves, and the coupling status of elemental utilization in the leaves under continuous cropping systems using natural (only soil; i.e., control soil, CO) and artificial (soil + straw + chicken + urea; i.e., straw mixture soil, ST) soil via monitoring studies for 11 years in a solar greenhouse. Soil organic C, total N, and total P concentrations increased by 63.4%, 72.7%, and 144.3% in the CO, respectively, after 11 years of cultivation (compared to the first year), and by 18.1%, 24.3%, and 117.7% in the ST under continuous cropping conditions, respectively. Total K concentrations remained unchanged in both soils. Moreover, the availability of these soil elements increased to different degrees in both soils after 11 years of planting. Additionally, the leaf P concentration increased by 9.8% in the CO, while leaf N and K concentrations did not change, suggesting decoupling of P utilization from that of N and K in leaves under a continuous cropping system. These findings suggest that imbalanced soil nutrients under continuous cropping conditions results in decoupling of P from N and K in the utilization of leaf nutrients.

Composition and function of rhizosphere microbiome of Panax notoginseng with discrepant yields

Background: Panax notoginseng is a highly valuable medicinal plant. Reduced P. notoginseng yield is a common and serious problem that arises in a continuous cropping system. Variation in the composition and function of soil microbial community is considered the primary cause of yield reduction.Methods: This study used shotgun metagenomic sequencing approaches to describe the taxonomic and functional features of P. notoginseng rhizosphere microbiome and screen microbial taxa and functional traits related to yields. Results: At the family and genus level, a total of 43 families and 45 genera (relative abundance > 0.1%) were obtained, and the correlation with the yield of P. notoginseng was further analyzed. Nitrosomonadaceae, Xanthomonadaceae, Mycobacterium and Arthrobacter that were enriched in soils with higher yields were positively correlated with P. notoginseng yields, thereby suggesting that they might increase yields. Negative correlation coefficients indicated that Xanthobacteraceae, Caulobacteraceae, Oxalobacteraceae, Chitinophagaceae, Sphingomonas, Hyphomicrobium, Variovorax and Phenylobacterium might be detrimental to P. notoginseng growth. A total of 85 functional traits were significantly (P < 0.05) correlated with P. notoginseng yields. Functional traits, likely steroid biosynthesis and MAPK signaling pathway were positively correlated with P. notoginseng yields. In contrast, functional traits, such as bacterial secretion system, ABC transporters, metabolism of xenobiotics by cytochrome P450 and drug metabolism–cytochrome P450, were negatively associated with yields. Conclusions: This study describes an overview of the rhizosphere microbiome of P. notoginseng with discrepant yields and identifies the taxa and functional traits related to yields. Our results provide valuable information to guide the isolation and culture of potentially beneficial microorganisms and to utilize the power of the microbiome to increase plant yields in a continuous cropping system.

Composition and function of rhizosphere microbiome of Panax notoginseng with discrepant yields

Background Panax notoginseng is a highly valuable medicinal plant. Reduced P. notoginseng yield is a common and serious problem that arises in a continuous cropping system. Variation in the composition and function of soil microbial community is considered the primary cause of yield reduction. Methods This study used shotgun metagenomic sequencing approaches to describe the taxonomic and functional features of P. notoginseng rhizosphere microbiome and screen microbial taxa and functional traits related to yields. Results A total of 43 families and 45 genera (relative abundance > 0.1%) were further confirmed to be related to P. notoginseng yields. Nitrosomonadaceae, Xanthomonadaceae, Mycobacterium and Arthrobacter that were enriched in soils with higher yields were positively correlated with P. notoginseng yields, thereby suggesting that they might increase yields. Negative correlation coefficients indicated that Xanthobacteraceae, Caulobacteraceae, Oxalobacteraceae, Chitinophagaceae, Sphingomonas, Hyphomicrobium, Variovorax and Phenylobacterium might be detrimental to P. notoginseng growth. A total of 85 functional traits were significantly (P < 0.05) correlated with P. notoginseng yields. Functional traits, likely steroid biosynthesis and MAPK signaling pathway were positively correlated with P. notoginseng yields. In contrast, functional traits, such as bacterial secretion system, ABC transporters, metabolism of xenobiotics by cytochrome P450 and drug metabolism–cytochrome P450, were negatively associated with yields. Conclusions This study describes an overview of the rhizosphere microbiome of P. notoginseng with discrepant yields and confirms the taxa and functional traits related to yields. Our results provide valuable information to guide the isolation and culture of potentially beneficial microorganisms and to utilize the power of the microbiome to increase plant yields in a continuous cropping system.

Effects of ridge and furrow film mulching on soil environment and yield under potato continuous cropping system

The effect of ridge and furrow film mulching (RFFM) on soil microbial communities, physicochemical property, enzymatic activity, and tuber yield were studied under the potato (Solanum tuberosum L.) continuous cropping fields managed for one (CY-1), two (CY-2) and four years (CY-4). Experimental treatments included a conventional flat plot without film mulching (FP) and five RFFM treatments: (i) a flat plot with film mulching (T1); (ii) on-ridge planting with full film mulching (T2); (iii) on-furrow planting with full film mulching (T3); (iv) on-ridge planting with half film mulching (T4); and (v) on-furrow planting with half film mulching (T5). Compared with FP, RFFM increased microbial communities, soil electrical conductivity, and enzymatic activities, and decreased pH values to improve the soil environment. Microbial communities of T2 and T5 were relatively higher, while soil urease and alkaline phosphatase activities of T2 and T4 were higher in all the continuous cropping years. In addition, the tuber yields of T2 were also increased by 75.0, 46.4 and 97.3% than FP, respectively. Thus, on-ridge planting with full film mulching (T2) is recommended as an adaptive management strategy for potato cultivation in the semi-arid areas where continuous cropping is necessary.

Long-Term Monoculture Negatively Regulates Fungal Community Composition and Abundance of Tea Orchards

Continuous cropping frequently leads to soil acidification and major soil-borne diseases in tea plants, resulting in low tea yield. We have limited knowledge about the effects of continuous tea monoculture on soil properties and the fungal community. Here, we selected three replanted tea fields with 2, 15, and 30 years of monoculture history to assess the influence of continuous cropping on fungal communities and soil physiochemical attributes. The results showed that continuous tea monoculture significantly reduced soil pH and tea yield. Alpha diversity analysis showed that species richness declined significantly as the tea planting years increased and the results based on diversity indicated inconsistency. Principal coordinate analysis (PCoA) revealed that monoculture duration had the highest loading in structuring fungal communities. The relative abundance of Ascomycota, Glomeromycota, and Chytridiomycota decreased and Zygomycota and Basidiomycota increased with increasing cropping time. Continuous tea cropping not only decreased some beneficial fungal species such as Mortierella alpina and Mortierella elongatula, but also promoted potentially pathogenic fungal species such as Fusarium oxysporum, Fusarium solani, and Microidium phyllanthi over time. Overall, continuous tea cropping decreased soil pH and potentially beneficial microbes and increased soil pathogenic microbes, which could be the reason for reducing tea yield. Thus, developing sustainable tea farming to improve soil pH, microbial activity, and enhanced beneficial soil microbes under a continuous cropping system is vital for tea production.

The Agrarian Village World of the Ohio Valley Indians

Explores Indian women’s involvement in environmentally shaping the agrarian landscape of the almost-thousand-mile-long Ohio River valley. Women planted their crops in riverway bottomlands and produced a surplus food supply that encouraged trade with nearby and distant villages. An extensive trading network preceded European arrival. Extensive cornfields, bountiful vegetable gardens, and fruit orchards characterized Indian villages along the Ohio’s tributary rivers. Indigenous women developed a stable, continuous cropping system that maintained the organic matter in the soils by not plowing, and this provided long-range village stability. Environmental abundance in the Ohio River valley sustained high population levels. Rivers and streams teemed with more than a hundred varieties of fish; lakes abounded with wildlife and 250 species of mussels. Villages were strategically located within landscape niches that ensured sedentism and increased village size. These niches, or openings, provided access to adjacent, fertile fields, rich wetlands with nutritional plants, and forests that supplied meat and furs. Numerous bison, elk, and deer herds populated the region. Wetlands food sources were breadbaskets, and even small wetland patches produced high yields of food resources.