Temme, Arnaud J.Schoorl, Jeroen M.van der Meij, W. Marijn
11页
查看更多>>摘要：We present a set of new geomorphometric variables that express landscape position relative to breaklines in hillslopes, and test whether these variables are of value in explaining soil property variation in three study sites in the United States, the Netherlands, and Spain. Underlying this work is the recognition that slope breaks, such as cliff lines, lynchets, and large slumped blocks, are associated with processes that affect soil formation around them. For each study site, we digitized slope breaks and calculated vertical and horizontal distance to the nearest lower and higher slope breaks, as well as the relative position between multiple slope breaks, the slope increase at the next higher slope break, and the slope decrease at the next lower slope break. We then assessed the value of these geomorphometric variables in the prediction of slope properties by simple linear regression. At each study site, models were fitted to existing soil observations using a traditional set of geomorphometric variables, and the traditional set plus our newly developed variables.& nbsp;Model comparison indicated that the new variables substantially improved model fit and reduced model error for the site in the United States (Kansas, n = 100), improved model fit but did not reduce model error for the site in the Netherlands (Limburg, n = 192), and did not solve model overfitting issues for the small dataset in Spain (Malaga, n = 66).
查看更多>>摘要：Alpha and beta diversities are widely used to assess microbial community dynamics. However, little is known about the optimum sampling times for microbial alpha and beta diversity analysis between various cropland management systems across seasons, and whether changes in alpha and beta diversities of bacteria and fungi in response to temporal variation are synchronized. To investigate shifts in microbial alpha and beta diversities between soil environments caused by cropland management during the transition from winter to summer, a longterm field experiment was conducted under three different conditions: (1) natural regeneration after the cropland was abandoned, (2) mineral fertilizer application alone, and (3) 7500 kg ha-1 of wheat straw combined with mineral fertilizers incorporated into the cropland. Illumina HiSeq sequencing was performed, targeting the bacterial 16S rRNA V4-5 and fungal ITS1 regions. The results showed that the alpha and beta diversities of bacteria and fungi responded differently to seasonal change, and the temporal changes in beta diversity between treatments were not synchronized with those of alpha diversity. Compared to fungi, seasonal change had a more complex influence on soil bacterial beta diversity due to the interaction between land management and sampling time. Thus, using only one or a few sampling times within a season is an oversimplified approach when assessing bacterial beta diversity between land management systems and the impacts of environmental factors on bacterial diversity. For soil fungi, it was possible to assess their beta diversity between management practices without considering temporal variation. This research provides an opportunity to assess the effects of temporal variation on microbial diversity under various land management styles.
查看更多>>摘要：In geoarchaeological soil phosphorus (P) prospection, the soil P content is determined to infer the (pre)historic anthropogenic land use of an area. In the past, most soil P prospections were applied to one soil depth. However, if the archaeologically relevant depth (i.e., past land surface) is not known, the prospection needs to take several depths into account. No satisfactory methodology exists for deducing archaeologically interesting depths (AID) from such vertical soil P data, even though this information could facilitate more targeted planning of archaeological excavations (i.e., which areas/depths to prioritize). In this paper, we develop a four-stage process to identify AID from vertical soil P data using as an example data from a case study on the Iron Age hillfort on the Altenburg/Niedenstein (Hesse, Germany). Our approach involves quantitative data evaluation of vertical soil P graphs, a pedological validation based on soil stratigraphy, and a regional validation based on the spatial distribution of identified AID. We found several AID on the Altenburg/Niedenstein hillfort, which largely align with the findings from archaeological research. The comparative evaluation of identified AID with an excavation report and soil stratigraphy suggests that (1) the size of the Iron Age hillfort largely corresponds with the outer rampart of the prehistoric settlement, but was exceeded in some places; (2) that a significantly larger area than formerly assumed might already have been used during the Neolithic. However, the results of the AID method remain tentative until tested in the field.
查看更多>>摘要：Plastic film mulch alters the soil environment and improves crop production. Although the response of aboveground parts of agroecosystems to plastic film mulch has been extensively studied, no studies have investigated the response of the soil microbiome to plastic film mulch and its effect on crop yield. Here, we performed a metaanalysis of 536 observations to elucidate the response of the soil microbial community to plastic film mulch. Plastic film mulch significantly increased soil microbial alpha-diversity (Shannon: +0.043, 95% CI: +0.022 to + 0.064; richness: +0.037, 95% CI: +0.007 to + 0.067), abundance (+0.104, 95% CI: +0.070 to + 0.139), and ecofunctionality (+0.129, 95% CI: +0.087 to + 0.170). In neutral pH soil and field combined plastic film mulch with ridge-furrow tillage, plastic film mulch had a significant impact on microbial richness. Microbial abundance increased significantly when chemical fertilizer was used, but not when organic fertilizer was used. The effect of low-level nitrogen on N acquisition enzyme actives is greater than that of medium and high nitrogen input. Thick film mulch produced a larger positive response in microbial abundance, C acquisition, and oxidative enzyme activities than thin film mulch. Changes in microbial functionality were decoupled with diversity, while in tandem with its abundance and community structure. The increases in microbial C acquisition, N acquisition, and oxidative enzyme activities were significantly linked to yield. Our findings highlight the beneficial effects of plastic film mulch on the soil microbial community and have further implications for the development of soil health-friendly agricultural management.
de Oliveira, Luiz Eduardo ZancanaroNunes, Rafael de Souzade Figueiredo, Cicero CelioRein, Thomaz Adolpho...
12页
查看更多>>摘要：Due to the strong interaction of phosphorus (P) with soil constituents, P fertilizer placement can significantly affect how crops take up this nutrient. Nonetheless, few studies address the spatial distribution of P at the rowinterrow scale according to management strategies. In a 16-yr no-tillage (NT) field experiment involving two different P fertilizer application methods (broadcast or band application) and two P sources (triple superphosphate - TSP or reactive Gafsa phosphate rock-RPR), plus a control treatment, the spatial distribution of P fractions was assessed in two occasions: after the 8th and the 16th crops. This was done vertically to a depth of 30 cm and horizontally from the crop row to the center of the interrows. Broadcast treatments showed total and Mehlich-1 P accumulation at the soil surface while for band application this accumulation was in the crop row region. A small P movement down the soil profile was observed from the 8th to the 16th crop with broadcast application, whereas with band fertilizer this effect was more noticeable, showing increased soil volume under P fertilizer influence even without soil tillage; it is likely that this was partly due to biological P turnover and application at depth. After 16 crops, the soil volume under the influence of P fertilizer was greater under band application while the volume above Mehlich-1 P critical levels for the 0-20 cm layer in regional studies was higher under broadcast application, independent of the P source. Soil organic carbon (SOC) contents were not affected by P placement or source. However, a significant accumulation of SOC was seen from the soil surface downwards after the last eight crops. The spatial distribution of P and SOC was better correlated under broadcast treatments, with high values for both variables at the soil surface; this may explain similar yields to those obtained with band application, where P fertilizer is placed near the main roots in an attempt to reduce P adsorption to the soil solid phase.
查看更多>>摘要：The long-term effects of different fertilization regimes on the microbial functional potential of soils involving nutrient cycling remain largely unknown. Here, metagenomic sequencing was applied to investigate the influences of long-term chemical and organic fertilization on soil microbial C and N cycling across southern, middle and northern sites of black soil region in Northeast China. The results showed that biogeographic distance induced the most influential on the microbial functional profiles of soil C and N cycling, and significant effects of manure fertilization were detected across three experimental sites. Organic fertilization enriched the relative abundances of Proteobacteria and Planctomycetes that carry C and N cycling genes, while inhibited the growth of oligotrophic groups such as Verrucomicrobia. Chemical fertilization increased the gene abundances involved in methane oxidation, but had little effect on soil C degradation and fixation. Contrarily, manure fertilization, particularly the combination of chemical and organic fertilizers (CFM), significantly decreased the abundance of cooC (reductive acetyl-CoA pathway) and coxS (CO oxidation) while enhanced the abundance of icd (rTCA cycle), which are involved in C fixation. Additionally, chemical fertilization enriched the gene abundance that involved in soil N degradation, nitrification and anammox, whereas manure fertilization was beneficial for the functional potentials of assimilatory and dissimilatory nitrate reductions across the black soils. However, CFM significantly promoted the soil denitrification potential, possibly due to excess N input, which might result in soil N loss via the emission of nitrogenous gas in this region. Furthermore, the substantial enhancement in soil P contents induced by manure addition predominantly affected the C and N cycling profiles, abundance of functional genes and microbial taxa. Moreover, diverse correlations between C and N cycling genes suggested the synergetic or antagonistic interactions of C and N metabolic potentials in the black soils. Overall, this study provided in-depth insights into distinct microbial functional potentials under long-term chemical and organic fertilization that may have predictable consequences for soil nutrient cycling in agroecosystems of black soil region.
查看更多>>摘要：The existing research into soil component inversion based on spectroscopic techniques has mainly focused on traditional statistical learning. However, the most prominent drawback of this approach is the difficulty in obtaining the soil components' sensitive bands with explanatory inversion mechanisms. Whether for soil organic matter inversion or soil heavy metal inversion, there is still a lack of inversion models based on the physical theory of remote sensing. Hence, in this paper, an inversion model based on thickness correction using Kubelka-Munk (K-M) theory is proposed. Firstly, in this study, a soil thickness observation experiment based on K-M theory was undertaken. The impact of the soil thickness and the material of the container on the spectra was explored by selecting different experimental samples with different background container materials. A modified K-M thickness model was then developed by combining indoor spectral data. This allows the corresponding scattering coefficients and absorption coefficients for soil samples with different organic matter contents to be calculated. The optimal organic matter inversion model can then be constructed by the scattering coefficients, with the sensitive band at 2.197 mu m. The results obtained in this study demonstrate the feasibility and superiority of the proposed method and further explain the sensitive bands of soil organic matter in hyperspectral data, with a determination coefficient accuracy of up to 0.97. The experimental results also demonstrate that the recom-mended soil thickness for soil samples should be more than 7 mm. In addition, when selecting background container materials, materials with obvious reflectance peak and valley characteristics should be avoided.
NSTL
Elsevier