Food security in the East African Highlands is dependent upon the productivity of lands managed by smallholders who face difficult challenges in maintaining the fertility of their soils. A study was conducted to identify indicators of soil fertility status that are consistent with farmers’ perceptions of soil fertility. Physical, chemical and biological properties of soils were measured from paired fields identified as either productive or non-productive by 12 farmers and compared to findings of a household survey on soil fertility management. Special attention was given to the potential of different soil organic matter fractions to serve as diagnostic indicators of soil fertility. Farmers’ criteria for distinguishing soil productivity included crop performance, soil tilth, moisture and colour and presence of weeds and soil invertebrates. All farmers attributed low fertility to inadequate use of organic and inorganic fertilisers (100%) and removal of crop residues (100%). Other causes included continuous cropping (83%), lack of crop rotation (66%) and soil erosion (42%). Productive soils had significantly higher soil pH, effective cation exchange capacity, exchangeable cations, extractable P and total N and P than non-productive soils. Total organic C and several estimates of soil labile C including particulate organic C (POC), three Ludox density separates of POC, KMnO4-oxidizable C and microbial biomass C were significantly greater in productive soils. Soil microbial biomass N, net N mineralisation and soil respiration were also significantly higher in productive soils. Farmers’ perceptions of soil quality were substantiated through soil chemical analyses and soil organic matter fractions provided precise information on these differences. The similarity of soil physical properties in productive and non-productive fields suggests that differences in chemical and biological indicators may have resulted, in part, from smallholders’ management and are not inherent properties of the soils.
Tag: chemical properties
Soil chemical properties dynamics as affected by land use change in the humid forest zone of Cameroon
The conversion of forests to other forms of land use has profound effects on the distribution and supply of soil nutrients. Understanding the effects of land use on soil is essential for addressing agroecosystem transformation and sustainable land productivity. Although soil carbon stock has been previously examined in the humid forest zone of Cameroon, the dynamic and interactions between other soil chemical properties has been poorly addressed to date. The present study used the quadrat approach to assess the effect of four land use types (secondary forest, fallow, cocoa plantation and mixed cropping) on soil chemical properties. Soil samples were collected at two different depths (0-10, 10-30 cm) in all land use types and analyzed for pH, total carbon, soil organic carbon, total nitrogen, cation exchange capacity (CEC), calcium (Ca), potassium (K), magnesium (Mg) and boron (B). Land use type significantly affected B, Ca, K and pH: in general, these properties were higher in cocoa plantation and mixed cropping than in secondary forest and fallow. All soil properties were significantly greater in the upper than in the lower soil depth. In addition, all soil properties differed significantly among sites and villages within sites. Pearson correlations between soil chemical properties were positive and generally significant in the four land use types, except for some correlations with B, pH and CEC. Despite the fact that some of the fundamental soil chemical properties (carbon, nitrogen, CEC and Mg) did not differ among the four land use types, high density tree-based production systems are recommended for the storage of these elements in the soils.
Soil Spectroscopy: An Alternative to Wet Chemistry for Soil Monitoring
The soil science community is facing a growing demand of regional, continental, and worldwide databases in order to monitor the status of the soil. However, the availability of such data is very scarce. Cost-effective tools to measure soil properties for large areas (e.g., Europe) are required. Soil spectroscopy has shown to be a fast, cost-effective, environmental-friendly, nondestructive, reproducible, and repeatable analytical technique. The main aim of this paper is to describe the state of the art of soil spectroscopy as well as its potential to facilitating soil monitoring. The factors constraining the application of soil spectroscopy as an alternative to traditional laboratory analyses, together with the limits of the technique, are addressed. The paper also highlights that the widespread use of spectroscopy to monitor the status of the soil should be encouraged by (1) the creation of a standard for the collection of laboratory soil spectra, to promote the sharing of spectral libraries, and (2) the scanning of existing soil archives, reducing the need for costly sampling campaigns. Finally, routine soil analysis using soil spectroscopy would be beneficial for the end users by a reduction in analytical costs, and an increased comparability of results between laboratories. This ambitious project will materialize only through (1) the establishment of local and regional partnerships among existent institutions able to generate the necessary technical competence, and (2) the support of international organizations. The Food and Agriculture Organization (FAO) of United Nations and the Joint Research Centre of the European Commission are well placed to promote the use of laboratory and field spectrometers for monitoring the state of soils.
Permafrost Wetlands Are Sources of Dissolved Iron and Dissolved Organic Carbon to the Amur-Mid Rivers in Summer
Dissolved iron (dFe) transported by the Amur River greatly contributes to phytoplankton growth in the Sea of Okhotsk. Nevertheless, there has been little research on the source of dFe to rivers, especially in the Amur-Mid Basin, which is situated in a sporadic permafrost area. In the Amur-Mid Basin, permafrost generally exists in wetlands in flat valleys, and these permafrost wetlands could be a source of dFe to rivers. To assess the importance of permafrost wetlands for dFe export, we conducted a local survey on land and soil characteristics of wetlands, and moreover analyzed the chemical composition (dFe, dissolved organic carbon [DOC], pH, and electrical conductivity [EC]) of 24 rivers with different watershed sizes in summer. As a result of local survey, the thickly accumulated peat soils in the permafrost wetland were almost saturated and rich in organic matter from the surface to a greater depth near the permafrost table. In addition, the coverage of such permafrost wetlands in watersheds showed significant positive correlations with dFe (r2 = 0.67, p = 1.7e−6) and DOC (r2 = 0.48, p = 1.8e−4) and a negative correlation with EC (r2 = 0.52, p = 7.7e−5). The dFe concentration was also correlated well with DOC concentration (r2 = 0.68, p = 7.3e−7) but not correlated with pH and watershed area. These findings are the first to indicate that permafrost wetlands in the Amur-Mid Basin considerably contribute to dFe and DOC export to rivers, and their coverage primarily determines riverine dFe and DOC concentrations in summer.
Polyaspartic acid enhances the Cd phytoextraction efficiency of Bidens pilosa by remolding the rhizospheric environment and reprogramming plant metabolism
The green soil chelator polyaspartic acid (PASP) can enhance heavy metal phytoextraction efficiency, but the potential mechanisms are not clearly understood from the whole soil–plant system. In this study, we explored the effects and potential mechanisms of PASP addition in soils on plant growth and cadmium (Cd) uptake in the Cd hyperaccumulator Bidens pilosa by analysing variations in chemical elements, rhizospheric microbial community, and plant metabolomics. The results showed that PASP significantly promoted the biomass yield and Cd concentration in B. pilosa, leading to an increase in the total accumulated Cd by 46.4% and 76.4% in shoots and 124.7% and 197.3% in roots under 3 and 6 mg kg−1 PASP addition, respectively. The improved soil-available nutrients and enriched plant growth-promoting rhizobacteria (e.g., Sphingopyxis, Sphingomonas, Cupriavidus, Achromobacter, Nocardioides, and Rhizobium) were probably responsible for the enhanced plant growth after PASP addition. The increase in Cd uptake by plants could be due to the improved rhizosphere-available Cd, which was directly activated by PASP and affected by the induced rhizobacteria involved in immobilizing/mobilizing Cd (e.g., Sphingomonas, Cupriavidus, Achromobacter, and Rhizobium). Notably, PASP and/or these potassium (K)-solubilizing rhizobacteria (i.e., Sphingomonas, Cupriavidus, and Rhizobium) highly activated rhizosphere-available K to enhance plant growth and Cd uptake in B. pilosa. Plant physiological and metabolomic results indicated that multiple processes involving antioxidant enzymes, amino acids, organic acids, and lipids contributed to Cd detoxification in B. pilosa. This study provides novel insights into understanding how soil chelators drive heavy metal transfer in soil–plant systems.
Infrared Spectroscopy
Infrared Diffuse Reflectance Spectroscopy is a rapid, high throughput method for characterizing the chemical composition of materials.
Measuring Soil Quality Indicators under Different Climate-Smart Land Uses across East African Climate-Smart Villages
The present study assessed soil physical-chemical characteristics as reliable soil health indicators in six climate-smart land use types; agroforestry, community forest, cropland with soil and water conservation (SWC), crop land without SWC, grassland and control across climate-smart villages (CSVs) in Lushoto (Tanzania), Hoima (Uganda), Wote and Nyando (Kenya). Soils were sampled at three depths; 0–15 cm, 15–45 cm and 45–100 cm and then analyzed for bulk density (BD), pH, exchangeable bases (Ca, Mg, K, Na), extractable Fe, Mn, Zn, exchangeable acidity (ExAc), Electrical conductivity (EC), total carbon (TC), total nitrogen (TN) and cation exchange capacity (CEC). Land use types and sampling depths significantly affected soil properties (p < 0.05), High bulk density (BD) was measured at 45–100 cm depth in grassland (1.47 g/cm3) and crop land (1.50 g/cm3) in Kenya and Tanzania, respectively. BD in Ugandan grasslands was statistically lower (p < 0.05) than BD in other land use types at all depths. Soil pH of surface soil (0–15 cm) ranged from 6.67 ± 0.67 (agroforestry) to 6.27 ± 0.85 (grassland). Ex. bases (Ca, Mg, K and Na) and extractable Fe, Mn, Zn, ExAc, EC, TC, TN and CEC were significantly affected by land uses (p ≤ 0.05). Soil properties were significantly correlated, a positive correlation between silt % (p < 0.01) and pH, sand and Ca (p < 0.05). EC and pH, exchangeable Ca, exchangeable bases, exchangeable K and C: N ratio was observed. There was a negative correlation (p < 0.05) between pH and clay. The study has shown that improving soil properties using land use systems leads to an increase in soil nutrients.
Portable X-ray fluorescence (pXRF) calibration for analysis of nutrient concentrations and trace element contaminants in fertilisers
With the increasing popularity of local blending of fertilisers, the fertiliser industry faces issues regarding quality control and fertiliser adulteration. Another problem is the contamination of fertilisers with trace elements that have been shown to subsequently accumulate in the soil and be taken up by plants, posing a danger to the environment and human health. Conventional characterisation methods necessary to ensure the quality of fertilisers and to comply with local regulations are costly, time consuming and sometimes not even accessible. Alternatively, using a wide range of unamended and intentionally amended fertilisers this study developed empirical calibrations for a portable handheld X-ray fluorescence (pXRF) spectrometer, determined the reliability for estimating the macro and micro nutrients and evaluated the use of the pXRF for the high-throughput detection of trace element contaminants in fertilisers. The models developed using pXRF for Mg, P, S, K, Ca, Mn, Fe, Zn and Mo had R2 values greater or equal to 0.97. These models also performed well on validation, with R2 values greater or equal to 0.97 (except for Fe, R2val = 0.55) and slope values ranging from 0.81 to 1.44. A second set of models were developed with a focus on trace elements in amended fertilisers. The R2 values of calibration for Co, Ni, As, Se, Cd and Pb were greater than or equal to 0.80. At concentrations up to 1000 mg kg-1, good validation statistics were also obtained; R2 values ranged from 0.97–0.99, except in one instance. The regression coefficients of the validation also had good prediction in the range of 0–100 mg kg-1 (R2 values were from 0.78–0.99), but not as well at lower concentrations up to 20 mg kg-1 (R2 values ranged from 0.10–0.99), especially for Cd. This study has demonstrated that pXRF can measure several major (P, Ca) and micro (Mn, Fe, Cu) nutrients, as well as trace elements and potential contaminants (Cr, Ni, As) in fertilisers with high accuracy and precision. The results obtained in this study is good, especially considering that loose powders were scanned for a maximum of 90 seconds without the use of a vacuum pump. Copyright: © 2022 Acquah et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Volatile Constituents of Endophytic Fungi Isolated from Aquilaria sinensis with Descriptions of Two New Species of Nemania
Algae, bacteria, and fungi, as well as higher plants, produce a wide variety of secondary metabolites known as natural products. Natural products are well known as remarkable sources of many therapeutic agents. The genus Nemania is a wood-decaying fungus that belongs to family Xylariaceae. Nemania is often found as an endophyte in diverse hosts and some species are known to produce useful secondary metabolites. In this study, two Nemania species were isolated as an endophytic fungus from Aquilaria sinensis. Multi-gene phylogenetic studies showed that the newly described strains of Nemania are new to science, and this is the first report of Nemania from the host Aquilaria. One of the fermented species, Nemania aquilariae (KUMCC 20-0268), resulted in five sesquiterpenoids, which were previously reported from agarwood, and their structures were identified by gas chromatography-mass spectrometry (GC-MS). In addition, five different media were investigated in vitro to optimize conditions for growing the fungal biomass of Nemania aquilariae and N. yunnanensis.
Long-term effects of integrated soil fertility management practices on soil chemical properties in the Sahel
Joint application of mineral and organic fertilizers and incorporation of legumes into cropping systems, known as integrated soil fertility management (ISFM), has improved short-term crop productivity in sub-Saharan Africa. Little research exists, however, on the effectiveness of long-term ISFM in improving soil quality and productivity. This study determined the long-term effects of different ISFM treatments on soil chemical properties and OM dynamics up to 20 cm soil depth at a long-term research site at Saria, Burkina Faso. The ISFM treatments applied from 1960 to 2008 included broadcasted fertilizer (100 kg ha−1 14-23-14 (NPK) with 50 kg ha−1 urea; and NPK with an additional 50 kg ha−1 urea and 50 kg ha−1 KCl) supplemented with crop residue retention, and with manure application at 5000 or 40000 kg ha−1. In addition, continuous cropping of Sorghum bicolor (sorghum) was compared to yearly rotation between sorghum and Vigna unguiculata (cowpea). The large manure rate (40,000 kg ha−1) supplement was most effective in buffering fertilizer-application-induced pH decline and increasing grain yield, soil carbon (C), nitrogen (N), and phosphorus (P) concentrations (p < 0.05). Manure application also enhanced the microbial cycling and retention of C and N microbial byproducts compared to other fertilizer treatments, as indicated by C and N X-ray Absorption Near Edge Structure (XANES) spectroscopies. Legume-cereal cropping led to increased abundance of C and N functional groups indicative of reduced OM breakdown compared to the continuous cropping system. Supplemental application of manure with mineral fertilizers under mixed cereal-legume cropping was found to be most effective in improving long-term soil fertility and crop productivity in the Sahel.