Rodriguez-Ramos, Jean C.Scott, NatalieMarty, JaymeeKaiser, Daniel...
11页
查看更多>>摘要：Currently, there are substantial knowledge gaps on the impacts of cover crops on soil resources in tree cropping systems, wherein they are typically planted in interrow alleys and maintained for multiple years. While cover crops uptake soil nutrients and water, they can also prevent soil water evaporative losses and return nutrients to soils via decomposition of plant residues and stimulation of microbial nutrient cycling. This field sampling study examined variances in soil conditions across 5-and 7-year-old, cover cropped pecan orchards. We collected soil beneath cover crops and beneath adjacent trees, where soil was kept bare, to evaluate impacts of cover on the soil biota, nutrients, carbon, and their dynamics across a production season. We employed routine soil chemical analyses, phospholipid fatty acid (PLFA) analysis, and high throughput sequencing of 16 S rRNA genes and ITS regions for soils collected at four time points. We revealed that the cover cropped alley soils contained higher relative abundances of microbes that use labile soil substrates in resource rich conditions than did the tree row soils. Soil chemical analyses provided additional evidence that the cover crops did not deplete soil nutrients and reduce soil moisture, but rather, enhanced soil nutrient and moisture contents during many of the sampling time points. Notably, cover crop plant species correlated with soil nutrients and plant beneficial microbes, which may warrant consideration when selecting cover crop species. The tree row and cover cropped alley soils had different proportions of plant-beneficial mycorrhizal fungi. The tree rows supported higher numbers of ectomycorrhizal (ECM) fungi and alleys had higher relative abundances of arbuscular mycorrhizal (AM) fungi, suggesting potential benefits for tree species like pecan, which support dual colonization by AM and ECM Fungi. Altogether, the cover crops enhanced soil carbon, nutrients, and microbial populations in a pecan orchard and these impacts were frequently larger in a 7-year-old versus 5-year-old orchard.
查看更多>>摘要：Reclamation has been widely used to alleviate the degradation of cultivated upland and support the increasing grain demand. However, the response of soil ecosystem functioning and soil health to the reclamation of coastal wetlands remains unclear. A reclaimed soil chronosequence over 1000 years in Hangzhou Bay, China, was analyzed to assess two key approaches to evaluate soil health. We used the minimum data set along with the soil quality index (SQI) area and the sensitivity-resistance approaches. The physicochemical properties of the reclaimed soils changed drastically at the initial stage (during the first 60 years) but only marginally thereafter. Owing to continuous freshwater irrigation, plant cultivation, fertilization, and desalination, from natural tidal flats converted to vegetable fields, the SQI and soil multifunctional index increased along the reclamation chronosequence. The soil properties sensitive to the reclamation of coastal wetlands (electrical conductivity, exchangeable potassium, and enzyme activities) explained most of the variation in the SQI area, followed by the resistance indicators. This suggests that small changes in the sensitivity indicators might have considerable impacts on the improvement of soil quality. The most resistant properties with the slowest changes included pH and physical characteristics-water content, bulk density, and aggregate size classes. The quality indicators identified for reclaimed soils in Hangzhou Bay based on the SQI area and sensitivity-resistance approaches can be useful for soil health evaluation for soils affected by natural and anthropogenic factors. These approaches and indicators can be effectively used to evaluate soil quality and develop sustainable agriculture.
查看更多>>摘要：Cover crops have multiple benefits, such as improving water quality, providing a green manure effect, and storing carbon in the soil. They can, however, reduce drainage significantly during key periods of hydrosystem recharge, especially in winter. The objective of this study was to evaluate the influence of cover crops and/or crop diversification at the watershed scale on water in the downstream watershed of the Aveyron River, based on three scenarios with different management practices. It is an illustrative case study of situations of water imbalance involving 1150 farms, with agricultural fields covering 40,000 ha, of which ca. 40% may be irrigated. The MAELIA model was used to simulate 10 years (2007-2016) of dynamics to estimate the influence of cover crops on water flows. Simulations showed that short-duration cover crops terminated in autumn generally had little influence on water: they decreased drainage slightly in autumn, but the recharge in winter compensated for this decrease and thus did not influence the water dynamics or yields of the succeeding cash crops. Although long-duration cover crops grow for a longer period and are sown more frequently in fields, they also had relatively little influence on water in the region, except for decreasing drainage. A scenario with long-duration cover crops and diversification of rotations was a good compromise for quantitative water management. Diversifying rotations, notably by replacing maize with crops that required less water, compensated for potential negative effects of long-duration cover crops. Although this scenario increased variability depending on the weather year and reduced autumn drainage, it influenced irrigation withdrawals and river flows little over the 10-year period. However, greater variability occurred at the field scale, where cover crops can have more influence. Thus, it is important to adapt the management practices for cover crops in rotations to decrease negative effects, particularly on water availability, which could increase withdrawals in an area that already has a water deficit, and not to decrease yields and thus farmers' profits. Our results are valid for the study area, but these scenarios should be extrapolated to other soil and climate conditions and other rotations and management systems.
查看更多>>摘要：Fusarium wilt of banana, also known as Panama disease, caused by the pathogen Fusarium oxysporum f. sp. cubense tropical race4 (Foc4) is one of the most destructive diseases and currently threatens banana production around the world. In this study, pot and field experiments were conducted to assess the control effect of banana intercropping with five intercropping green manures (Crotalaria acicularis, Sesbania sesban, Melilotus officinalis, Vicia villosa and Trifolium repens) on banana Fusarium wilt in high disease incidence soil. The soil microbiome was analysed using the MiSeq Illumina sequencing platform. The results showed that compared with banana monoculture, five intercropping treatments significantly reduced the incidence of banana Fusarium wilt and decreased the richness and diversity of soil fungi, among which V. villosa and T. repens intercropping treatment showed greater effect in disease suppression than the other treatments. The abundance of Aspergillus was increased, while the number of culturable Fusarium oxysporum was decreased in all five intercropping treatments compared with the banana monoculture treatment. A structural equation model showed that the changes in soil organic matter and NH4+-N content caused by intercropping may play a key role in the change of the soil fungal community and the reduction of banana Fusarium wilt incidence. In summary, this study provides an approach to intercropping green manures to unravel the biological basis of the disease-suppressing microbiome in the context of agricultural practices and soil management.
查看更多>>摘要：Viruses interact with nearly all organisms on Earth, thereby influencing biogeochemical cycles, agriculture, and health. However, less is known about the composition and function of viruses in agricultural rhizosphere soils, especially under consecutive monoculture regimes. Our qRT-PCR analysis in this study showed that consecutive monoculture regimes significantly increased the content of pathogenic Broad bean wilt virus 2, Turnip mosaic virus, and Cucumber mosaic virus in Radix pseudostellariae roots at different growth stages. Metatranscriptome analysis indicated that consecutive monoculture altered the rhizosphere soil viral community structure, composition, and habitat niche breadth and accumulated pathogenic plant viruses in the rhizosphere soil. In addition, 54 unique carbohydrate metabolism-related open reading frames (ORFs) were detected as encoding carbohydrate-active enzymes (CAZymes) in viromes, including glycoside hydrolases and glycosyl-transferase activities. Our results also showed that the soil viral richness and the Shannon index displayed a negative cor-relation with bacterial abundance and a positive correlation with fungal abundance. Soil pH, total nitrogen, available phosphorus, and phenolic acids were the key abiotic drivers of the soil viral community composition. Our study provides new insights into how consecutive monoculture regimes shape the soil viral community composition and further influence plant viral diseases.
NSTL
Elsevier