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Metawee Jantamenchai, , Duangsamorn Tulaphitak, Wanwimon Mekboonsonglarp, Patma Vityakon
Published: 22 September 2021
Abstract:
The addition of organic materials can improve soil fertility and phosphorus availability in agricultural soils. However, knowledge of organic P (Po) forms in soils with the incorporation of different quality residues is limited. This study investigated Po forms and determined the relationship between Po and soil properties in tropical sandy soils after application of local organic residues of different qualities, including groundnut stover (GN), tamarind leaf litter (TM), dipterocarp leaf litter (DP), and rice straw (RS). The Po forms were determined using a sequential extraction procedure and 31P nuclear magnetic resonance (NMR) spectroscopy. Addition of residues, regardless of quality, had little effect on total Po accumulation, but it affected soil Po forms. Labile Po was a dominant form after incorporating high-quality residue (high nitrogen, low lignin, and low polyphenols) (e.g., GN), whereas nonlabile humic-Po and residual Po were dominant forms in soils treated with lower-quality residue with low N, high lignin, and high polyphenols (e.g., TM, DP, and RS). Using 31P NMR spectroscopy, orthophosphate and phosphate monoester (mono-P) were the major forms of inorganic P and organic P in all residue-treated soils, respectively. High-quality residue incorporation increased diester, DNA, and teichoic acid. The results showed that phosphonate occurred in GN soil because of acidic conditions occurring when GN was applied. The Po forms in lower-quality residue additions were dominated by mono-P because these residues had elevated contents of lignin and polyphenols, which has the potential to produce humic substances that form complexes with soil minerals. Furthermore, the nonlabile Po had a positive association with available P in tropical sandy soils.
Samad Emamgholizadeh,
Published: 6 August 2021
Abstract:
Soil cation exchange capacity (CEC) strongly influences the chemical, physical, and biological properties of soil. As the direct measurement of the CEC is difficult, costly, and time-consuming, the indirect estimation of CEC from chemical and physical parameters has been considered as an alternative method by researchers. Accordingly, in this study, a new hybrid model using a support vector machine (SVM), coupling with particle swarm optimization (PSO), and integrated invasive weed optimization (IWO) algorithm is developed for estimating the soil CEC. The physical and chemical data (i.e., clay, organic matter (OM), and pH) from two field sites of Taybad and Semnan in Iran were used for validating the new proposed approach. The ability of the proposed model (SVM-PSOIWO) was compared with the individual model (SVM) and the hybrid model (SVM-PSO). The results of the SVM-PSOIWO model were also compared with those of existing studies. Different performance evaluation criteria such as RMSE, R 2, MAE, RRMSE, and MAPE, Box plots, and scatter diagrams were used to test the ability of the proposed models for estimation of the CEC values. The results showed that the SVM-PSOIWO model with the RMSE (R 2) of 0.229 Cmol + kg−1 (0.924) was better than those of the SVM and SVM-PSO models with the RMSE (R 2) of 0.335 Cmol + kg−1 (0.843) and 0.279 Cmol + kg−1 (0.888), respectively. Furthermore, the ability of the SVM-PSOIWO model compared with existing studies, which used the genetic expression programming, artificial neural network, and multivariate adaptive regression splines models. The results indicated that the SVM-PSOIWO model estimates the CEC more accurately than existing studies.
Rentian Ma, , Jingfang Liu, Shiwei Zhao
Published: 3 July 2021
by 10.1007
Journal of Soils and Sediments pp 1-10; https://doi.org/10.1007/s11368-021-03011-z

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, Alfredo A.P. Xavier, , Patrícia P.A. Oliveira, , , Ladislau Martin-Neto
Published: 17 April 2021
Soil and Tillage Research, Volume 211; https://doi.org/10.1016/j.still.2021.105001

Abstract:
Agricultural areas under integrated production systems, such as Integrated Crop-Livestock-Forest System (CLFS), have the potential to sequestrate carbon (C) since both Soil Organic Matter (SOM) content and trees biomass increase thus mitigating the emission of greenhouse gases (GHGs) from agriculture. Regarding soil aspects, the C content stands out as the main indicator, but the structural aspect of SOM is also relevant since it plays a key role in the chemical stability of C compounds and the soil lifetime of C compounds. Laser-Induced Fluorescence Spectroscopy (LIFS) is an effective technique to evaluate the SOM humification index (HLIFS) from practically intact whole soil samples under different agricultural systems. Thus, the objective of this study was to analyze the SOM humification index in different integrated systems, such as Integrated Crop-Livestock-Forest System (CLFS), Integrated Livestock-Forest System (LFS), Integrated Crop-Livestock System (CLS), and in references areas, such as Intensive Pasture (INT), Extensive Pasture (EXT) and Native Forest (NF). For this purpose, samples of Red-yellow Latosol (Haplorthox by Soil taxonomy) from the experimental site located at Embrapa Pecuária Sudeste (Southeast of Brazil) were collected five years after the establishment of the integrated systems. Samples were collected at soil depths of 0–5, 5–10, 10–20, 20–30, 30–40, 40–60, 60–80, and 80–100 cm. Pellets of the whole soil samples were prepared for LIFS analysis. In these areas, SOM humification indices (HLIFS) presented the following descending order: CLS > EXT > INT > LFS > CLFS > NF. Previous results have shown a greater soil organic carbon stock in these integrated production systems than in the NF area, suggesting C sequestration in agricultural soil. In the present study, SOM was classified by LIFS as more chemically stable in integrated production systems than in native vegetation. Higher amounts of fluorescent compounds were identified from LIFS data, probably resulting from condensed aromatic groups. SOM with more recalcitrant groups normally has a longer lifetime in the soil, indicating a long-term contribution to mitigating climate change by avoiding fast SOM decomposition and CO2 return to the atmosphere. Also, for the first time, this study was able to identify a positive correlation (R = 0.79) between the SOM humification index (HLIFS) and the Cation Exchange Capacity (CEC)/C content ratio of whole soil samples, another innovative contribution from soil LIFS analyses.
, Michel K. Yao
Published: 27 January 2021
Journal of Environmental Management, Volume 283; https://doi.org/10.1016/j.jenvman.2021.112002

Abstract:
Conversion of natural forest to anthropogenic land use systems (LUS) often leads to considerable loss of carbon, however, proper management of these LUS may reverse the trend. A study was conducted in a semi-deciduous forest zone of Côte d’Ivoire to assess soil microbial functioning and soil organic carbon (SOC) stocks in varying tree stands, and to determine whether complex tree stands can mimic the natural forest in terms of these soil attributes. Tree plantations studied were monocultures of teak (Tectona grandis) and full-sun cocoa (Theobroma cacao L.), and a mixture of four tree species (MTS) with Tectona grandis, Gmelina arborea, Terminalia ivoriensis and Terminalia superba. An adjacent natural forest was considered as the reference. Each of these LUS had five replicate stands where soil (0–10 cm depth) samples were taken for physico-chemical parameters and microbial biomass-C (MBC), microbial activities, MBC/SOC ratio and metabolic quotient (qCO2). SOC and total N stocks were also calculated. The C mineralization rate (mg C–CO2 kg−1) and mineral N concentration (mg kg−1) drastically declined in the monocultures of cocoa (154.9 ± 29.3 and 49.8 ± 9.8, respectively) and teak (179.6 ± 27.1 and 54.1 ± 7.3) compared to the natural forest (258.4 ± 21.9 and 108.7 ± 12). However, values in MTS (194.7 ± 24.6 and 105.4 ± 7.4) were not significantly different from those in the natural forest. Similarly, SOC stocks in MTS (28.8 ± 1.9 Mg ha−1) were not significantly different from those recorded in the natural forest (32.9 ± 1.7 Mg ha−1) whereas teak (25.4 ± 1.7 Mg ha−1) and cocoa (23.1 ± 3.4 Mg ha−1) exhibited significantly lower values. Despite the acidic soil and recalcitrant litter conditions, increased MBC/SOC ratio and decreased qCO2 were recorded in the monocrops, suggesting a probable increase in the fungi/bacteria ratio. The complex MTS stand was found to mimic the natural forest in terms of soil microbial activity and organic status, due to the provision of a diversity of litter quality, which may serve as a basis for developing a climate smart timber system in West and Central Africa.
Published: 7 May 2020
European Journal of Agronomy, Volume 118; https://doi.org/10.1016/j.eja.2020.126090

Abstract:
The objective of this study was to assess the impact of different cotton (Gossipium hirsutum)-based management systems in the Brazilian Cerrado on soil’s physical and chemical quality, using multivariate analysis techniques. The experiment was conducted in areas of cotton production in the state of Mato Grosso, located in the Cerrado biome and Cerrado/Amazon ecotone. Soil samples were obtained from 1162 plots of 10 ha each to evaluate the effects of cotton production systems. These plots were distributed in the main production sub region of the state of Mato Grosso. Soil samples were obtained in the 0−20 cm layer to evaluate chemical quality, carbon and nitrogen content, texture and bulk density. Seed cotton yield was estimated by harvesting 4 rows, each of 5 m length. Clay contents varied from a low of 54 to a high of 778 g kg−1. Six cotton production clusters were established by means of a dendrogram. Principal component analysis explained almost 77% of all data variability, highlighting the effect of the evaluated soil attributes and altitude on cotton yields. The highest soil carbon (59.0 Mg ha−1) and nitrogen (3.5 Mg ha−1) stocks were observed in the clusters that used conservation agriculture practices. Clusters characterized by a high productivity were observed in regions with altitude of >600 m, but without any common soil parameters. Cotton production areas with the longest cultivation periods were characterized by having the highest soil fertility. The highest yields (4195 kg ha−1) of cotton in the state of Mato Grosso were obtained in regions with higher altitudes, associated with the use of conservation practices.
, Samuel T. Partey, Manfred Denich, Michael Kwaku, Christian Borgemeister,
Published: 6 May 2020
Agroforestry Systems, Volume 94, pp 1759-1780; https://doi.org/10.1007/s10457-020-00493-7

Abstract:
In the quest to promote bamboo agroforestry in the dry semi-deciduous forest zone of Ghana, we evaluated changes in soil properties, crop productivity and the economic potential of a bamboo-based intercropping system. The intercropping system was established from 3-months old sympodial bamboo (Bambusa balcooa) seedlings planted at a 5 m × 5 m spacing and intercropped with maize, cassava or cowpea. Separate monocropping fields for maize, cassava, cowpea and bamboo were set up adjacent to the intercropped field. In both the intercropping and monocropping fields, plots were with fertilizer treatments and without. The experiment was laid out in a split plot design with four replicates and studied over three years. Economic analysis was conducted using the financial benefit–cost ratio method. The results showed that regardless of fertilizer treatments, bamboo agroforestry and monocropped fields had comparable effects on soil properties and crop productivity within two years of establishment. In the third year, however, bamboo agroforestry had significantly (p < 0.05) higher soil moisture, pH and crop productivity levels. An intercropping advantage over monocropping was evident for all crops with respective partial land equivalent ratios for fertilized and non-fertilized intercropped systems as follows: cowpea (1.37 and 1.54), maize (1.38 and 1.36), and cassava (1.12 and 1.19). The economic evaluation also indicated marginal profitability of bamboo intercropping over monocropping systems. From the results obtained, there are clear indications that where bamboo is a prioritized woody perennial, integrated systems with crops may be encouraged.
Published: 20 April 2020
Abstract:
Integrated farming systems are sustainable strategies to intensify land productivity by combining annual crop, livestock and/or forestry activities in different spatio-temporal arrangements. Therefore, they may help tackle global food and energy insecurity and climate change in the coming decades. We investigated the effects of integrated crop-livestock (ICL) and integrated crop-livestock-forestry (ICLF) systems on quantity, quality, and origin of soil organic matter (SOM) in southeastern Brazil. A native forest and an extensive low-grazing intensity pasture system were used as references. In integrated systems, corn (Zea mays) was alternated with two consecutive years of piatã grass (Urochloa bryzantha) for cattle grazing. In ICLF, eucalyptus trees (Eucalyptus urograndis) were planted in simple rows of 15 × 2 m. Soil sampling was performed three times; in 2014, after two years of grazing; in 2015, after crop cultivation; and in 2016, after a successive grazing year, to evaluate chemical and physical composition changes of organic matter (C, N, δ13C, δ15N, and organic matter fractions) with time. Our findings showed that from 2010 to 2016, all systems (extensive grazing, ICL and ICLF) promoted increments on soil C and N stocks. However, land intensification converting extensive low-grazing intensity pasture to ICL was the most promising strategy, increasing soil C stocks at the rate of 0.28 Mg C ha−1 yr−1 from 2010 to 2016. Annual crop cultivation (corn intercropped with piatã grass) promoted high organic matter inputs on the soil, increasing the amount of soil labile organic matter fractions, which presented higher δ13C and lower δ15N values over time. SOM in the integrated farming systems was originated mainly from C4 plants. Therefore, optimizing development of piatã grass and corn increases organic residue inputs and then, soil C and N stocks. In addition, the crop period increased soil fertility parameters, which favors plant growth, thus providing high labile C inputs to the soil. In contrast, land intensification by adding the forestry component into the system (i.e., conversion from ICL to ICLF) reduced soil C (-0.22 Mg C ha−1 yr−1) and N (-0.03 Mg N ha−1 yr−1) stocks from 2010 to 2016, likely due to the reduction of C and N inputs to the soil caused by limited growth of annual crop and grass species under tree shades. In conclusion, land use intensification through ICL system contributes towards a more efficient and low-C agriculture, whereas the studied ICLF system did not bring further benefits to increase the quantity and/or quality of SOM.
Jingfang Liu, Zilong Wang, , Chenyang Xu, Rentian Ma, Shiwei Zhao
Published: 21 February 2020
Abstract:
Vegetation restoration is an effective way to rebuild degraded ecosystems and restore soil function. Soil surface electrochemical properties, including specific surface area, cation exchange capacity, surface charge density, surface electric field strength, and surface potential, are often used as indicators to evaluate agricultural soil quality and fertility. However, little attention has been payed to the effect of natural revegetation on soil surface electrochemical properties. In this work, we selected a grassland restoration chronosequence (slope cropland, 0 years; natural grasslands restored for 3, 8, 22 and 24 years, i.e. NR3, NR8, NR22 and NR24, respectively) to investigate the changes of soil surface electrochemical properties along with vegetative restoration. Our results showed that surface charge density and surface potential for restored grassland ranged from 0.16 to 0.20 C m−2 and from −94 to −109 mV, with an average of 0.18 C m−2 and −101 mV, respectively. The value of surface electric field strength could reach to the order of magnitude of −107 V m−1 and showed a decreasing trend with increasing period of natural vegetation recovery. Cation exchange capacity and specific surface area significantly increased with the extension of natural restoration period except for NR3 (P < 0.05). It was found that soil organic matter (SOM) and silt content were the main factors to determine cation exchange capacity and specific surface area. Both cation exchange capacity and specific surface area were closely related to silt content but weakly related to clay content, possibly due to the high silt content in our studied soils. Moreover, cation exchange capacity and specific surface area showed a significant linear relationship with SOM, which may be ascribed to the diversity in cation substitution sites and high specific surface area of SOM. Our results indicated that the long-term natural restoration of grassland contributed to the improvement of cation exchange capacity and specific surface area.
Yajie Zhu, Yiling Zhang, Huiying Chen, Yaqi Wang, Fuqian Cao, Weijun Sun, Xiaoyu Qi, Yucui Zhao,
Published: 1 January 2020
Current Microbiology, Volume 77, pp 425-433; https://doi.org/10.1007/s00284-019-01846-x

Abstract:
Glacier retreat may result in the decomposition of old organic carbon stored at the frontier of glacier retreat and the release of greenhouse gases such as CO2 and methane into the atmosphere. This process may gradually transform the soil in the region from its original status as a carbon sink into a carbon source, thus producing a positive feedback effect on global warming. In this study, Laohugou Glacier No. 12, Qilian Mountains, China, was taken as the research object, and the newly melted soil (Q1) at the frontier of glacier retreat and the sandy soil (Q2) on the bank of the nearby river were collected. The content of accumulation of organic matter (AOM) in Q1 soil was 5.56 ± 0.27 g/kg, and the total nitrogen was 0.60 ± 0.03 g/kg, which was significantly higher than that in Q2. The soil microbial carbon metabolism of Q2 was significantly (P < 0.01) higher than that of Q1 and the ability of organic matter to decompose was greater. The alpha diversity index of bacteria, fungi and archaea of Q2 was significantly higher than that of Q1. It may be that there were dominant species in Q1 causing the lower species evenness. The archaea metabolic function genes in Q1 were higher than those in Q2 because archaea are better adapted to a frozen environment. Bacterial carbohydrate and amino acid metabolism was abundant in Q2 and was related to microbial transformation of the carbon source into CO2.
Sang-Min Park, ,
Published: 18 February 2019
Journal of Hazardous Materials, Volume 369, pp 569-576; https://doi.org/10.1016/j.jhazmat.2019.02.061

Abstract:
In this study, we reviewed the selective adsorption and irreversible fixation of cesium (Cs+) on clay minerals. The selective adsorption of Cs+ results from reactions with frayed edge sites (FES) of clay minerals. The content of FES is about 0.1 ˜ 2.0% of the total cation exchange capacity (CEC). The fractionation of Cs+ in actual accident sites mainly exists as a residue, which is important because it is closely related to the strong binding between Cs+ and soils. Cs+ adsorbed onto FES can move into the deeper interlayer via weathering processes, thereby Cs+ can be irreversibly fixed in the interlayer of non-expanding 2:1 layered clay mineral. Additionally, Cs+ can be adsorbed in the interlayer of the expanding clay mineral and can be fixed by interlayer collapse. For this reason, Cs+ adsorption onto FES is defined as ‘selective adsorption’ subsequent sorption in the interlayer as ‘irreversible fixation’. Furthermore, the extended X-ray absorption fine structure (EXAFS) analysis can confirm that Cs+ bound to illite is coordinated with the outer surface (OOS) and interlayer surface oxygens (OIS) through FES or interlayer sites. Through these processes, Cs+ is adsorbed selectively onto FES, while Cs+ can subsequently move into the interlayer and become more strongly fixed.
, Viacheslav I. Adamchuk, , , Ashraf Ismail, Qianjun Gan, ,
Published: 23 January 2019
Geoderma, Volume 341, pp 111-128; https://doi.org/10.1016/j.geoderma.2019.01.006

Abstract:
In this research, proximal soil sensor data fusion was defined as a multifaceted process which integrates geospatially correlated data, or information, from multiple proximal soil sensors to accurately characterize the spatial complexity of soils. This has capability of providing improved understanding of soil heterogeneity for potential applications associated with crop production and natural resource management. To assess the potential of data fusion for the purpose of improving thematic soil mapping over the single sensor approach, data from multiple proximal soil sensors were combined to develop and validate predictive relationships with laboratory-measured soil physical and chemical properties. The work was conducted in an agricultural field with both mineral and organic soils. The integrated data included: topography records obtained using a real-time kinetic (RTK) global navigation satellite system (GNSS) receiver, apparent soil electrical conductivity (ECa) obtained using an electromagnetic induction sensor, and content of several naturally occurring radioisotopes detected using a mobile gamma-ray spectrometer. In addition, the soil profile data were collected using a commercial ruggedized multi-sensor platform carrying a visible and near-infrared (vis-NIR) optical sensor and a galvanic contact soil ECa sensor. The measurements were carried out at predefined field locations covering the entire study area identified from sensor measured a priori information on field elevation, ECa and gamma-ray count. The information was used to predict: soil organic matter (SOM), pH, lime buffer capacity (LBC), as well as concentration of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and aluminum (Al). Partial least squares regressions (PLSRs) were used to predict soil properties from individual sensors and different sensor combinations (sensor data fusion). By integrating the data from all of the proximal soil sensors, SOM, pH, LBC, Ca, Mg, and Al were predicted simultaneously with R2 > 0.5 (RPD > 1.50). Improved predictions were observed for most soil properties based on sensor data fusion than those based on individual sensors. After choosing the optimal sensor combination for each soil property, the predictive capability was compared using different data mining algorithms, including support vector machines (SVM), random forest (RF), multivariate adaptive regression splines (MARS), and regression trees (CART). Improved predictions for SOM, Ca, Mg, and Al were observed using SVM over PLSR. The predictive capability was followed by RF and MARS, with CART. Predictions of pH and LBC were only feasible using MARS and PLSR, respectively. In this field, it was not possible to predict extractable P and K using all tested sensor combinations or algorithms. With large variability in SOM, the field presents a special situation and thus, the result could be specific to the study site. Further research includes an extended number of experimental sites covering different geographic areas around Eastern Canada.
Pedro A. Sanchez
Properties and Management of Soils in the Tropics; https://doi.org/10.1017/9781316809785

Abstract:
Cambridge Core - Natural Resource Management, Agriculture, Horticulture and forestry - Properties and Management of Soils in the Tropics - by Pedro A. Sanchez
Pei-Pei Li, Yan-Lai Han, , ,
Published: 30 November 2018
Geoderma, Volume 338, pp 107-117; https://doi.org/10.1016/j.geoderma.2018.11.033

Abstract:
Long-term field fertilization trials have suggested that reduced chemical nitrogen (N) plus organic fertilization can effectively reduce N loss without sacrificing crop yield, while the knowledge of how organic fertilizers regulate soil microorganisms and their function in N transformation are limited. In this study, the response of net nitrification rate and the ammonia-oxidizer community within soil aggregates to long-term combined organic N and reduced chemical N fertilization was evaluated to understand the underlying mechanism of the practice in mitigating soil N loss. The fertilization experiment included an unfertilized control; chemical N fertilizer (N), superphosphate (P) and potassium sulfate (K) fertilizer (NPK); NPK plus straw (NPKS); and NPK plus manure (NPKM). The results showed that the large macro-aggregates mass (>2 mm) in soil significantly increased from 34.1% in NPK to 47.2% in NPKS (P < 0.05). NPKS and NPKM both had positive effects on soil moisture retention, total N (TN), soil organic carbon (SOC), ammonium (NH4+-N) and nitrate (NO3−-N) accumulation, particularly within micro- (<0.25 mm) and small macro-aggregates. Compared with the NPK treatment, soil net nitrification rate (NNR) and ammonia-oxidizing bacterial (AOB) abundance decreased by 67.1% and 40.7% respectively under NPKS (P < 0.05), and the decrease mainly appeared in large macro-aggregate and micro-aggregates. The net nitrification rate was significantly correlated with ammonia-oxidizing archaea (AOA) abundance only in small macro-aggregates (r = 0.642, n = 12, P < 0.05). In contrast, NRR was positively correlated with AOB abundance within small macro- and micro-aggregate size classes (r values ranged from 0.654 to 0.813, P < 0.05). The community structure of AOB varied among different fertilization treatments, while AOA community differentiation was mainly dependent on aggregate size. The shift of the AOA and AOB communities corresponded with high moisture and lower ammonia content in the large macro-aggregates and were potentially responsible for the suppressed nitrification activity in the NPKS treatment. These results indicated that reduced chemical N plus organic fertilization is beneficial for increasing N concentration in large macro-aggregates.
Published: 1 November 2018
Agronomy Journal, Volume 110, pp 2576-2586; https://doi.org/10.2134/agronj2018.02.0074

Abstract:
A multi-year experiment was conducted in the sandy, acidic soils of Happy Valley–Goose Bay (HV-GB), Newfoundland and Labrador, Canada to evaluate the effects of hardwood biochar on soil fertility, and to ascertain its nutrient supplying capability when applied singly or in combination with fishmeal and chemical fertilizers. The experiment was set up on a permanent layout and in a randomized block design with 10 treatments resulting from combinations of biochar (20 Mg C ha–1) with half and full recommended doses of fertilizers and fishmeal. In the control and biochar only treatments the beet (Beta vulgaris L.) seedlings did not grow at all, and in the fertilizer or fishmeal alone treatments the survival, growth, and biomass yields were severely affected. However, biochar application along with fertilizer or fishmeal enhanced crop establishment, growth, and yields. Biochar application increased topsoil pH by 0.5 unit and availability of Ca, K, and Mn by 186, 19, and 2.6 mg L–1, respectively. Plant tissue contents of N, Mg, Fe, Mn, and Zn were greater in non-biochar treatments (NBT) than in biochar treatments (BT), but the opposite was found for K. Despite greater nutrient contents in NBT for some elements, plant uptake (kg ha–1) of nutrients in BT were always much greater than NBT due to higher biomass yield in BT. The positive effects of biochar observed in this study demonstrate that biochar has the potential to enhance soil fertility and crop productivity of sandy, acidic soils that are similar to the regional soils of Labrador. Copyright © 2018. . Copyright © 2018 by the American Society of Agronomy, Inc.
, Valentin Sohy, Claire Chenu, , Jean-Thomas Cornelis
Frontiers in Environmental Science, Volume 6; https://doi.org/10.3389/fenvs.2018.00116

Abstract:
The limitations of conventional agriculture have accelerated the need for a transition to an environmentally and economically sustainable agricultural model. In this regard, the role played by soil organic matter (SOM) is key. Here, we aimed to study the impact of permaculture and biointensive micro-gardening practices, characterized by intensive cultivation, the use of large and localized organic inputs and the non-use of mineral fertilizers and pesticides, on soil physicochemical properties and SOM distribution in aggregate-size fractions. The physicochemical properties of soils in permaculture farming implemented for 7 years were compared with a soil under pasture. A soil experiencing conventional agriculture practices in similar geopedoclimatic conditions was simultaneously studied. Soils were separated into four aggregate-size fractions, into which organic carbon (OC) concentrations have been measured. The major soil physicochemical properties were measured on the bulk soils. The concentrations of total OC and nitrogen (N) in bulk soils were higher under permaculture practices, due to significant inputs of manure and compost, resulting in higher concentrations of the bioavailable nutrients Ca, Mg, K, and P. The permaculture practices sustained a level of macroaggregation similar to that of the pasture, and well above that of conventional practices. OC concentrations increased in the 250–2,000, 50–250 μm and occluded 50–250 μm fractions, but not in the <50 μm fraction compared to pasture. This can be explained by the too short duration of permaculture practices for allowing the decomposition of coarse particulate organic matter (POM) into fine sized SOM that is more associated with mineral particles. The higher OC stocks in permaculture are therefore mainly governed by the coarse POM fraction. Our results show that permaculture/biointensive micro-gardening practices enhance SOM storage and modify the distribution of SOM in aggregate-size fractions, while substantially improving nutrient bioavailability and suggest that these practices strongly affect soil properties. The effects of permaculture practices on soil properties would certainly vary depending on geopedoclimatic context, justifying the need to implement the approach for other soil types. Finally, we recommend to compare biogeochemical budget and nutrients use efficiency of permaculture gardening with conventional horticulture gardening.
Fengyan Zhao, Yongyong Zhang, Wenge Dong, Chongjun Zhou, Guoxian Zhang,
Soil Science and Plant Nutrition, Volume 64, pp 782-792; https://doi.org/10.1080/00380768.2018.1520049

Abstract:
In order to obtain high tomato production, chemical fertilizers have been intensively applied in solar greenhouse in Northern China. This unreasonable use of chemical fertilizers always leads to soil degradation. One of the most serious problems is the loss of exchangeable base cations: calcium (Ca), magnesium (Mg), and potassium (K), and available micronutrients: iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn). We collected soils with different tomato cultivation durations: 0, 5, and 20 years, to investigate the effects of different fertilizers on the dynamics of soil base cations and micronutrients which extracted by 1 M ammonium acetate and 0.005 M diethylenetriaminepentaacetic acid, respectively. Five treatments were included: no fertilizer application as control (Con), chemical nitrogen, phosphorus and potassium fertilizers (CF), rice straw (FS), chicken manure (CM), and vermicompost (VM). Our results show that soil exchangeable Ca significantly decreased with the increase of cultivation duration, whereas soil exchangeable K increased due to the fertilization of K. Soil exchangeable Ca and K exhibited decreasing trends during the growth season of tomato, but not exchangeable Mg. Long-term tomato cultivation significantly increased soil available micronutrients. Soil available Fe and Mn fluctuated sharply during the growing season of tomato plant. Except Zn, fertilizers exhibited no constant significant effect on base cations and micronutrients. After long term planting of tomato, the loss of exchangeable Ca, but not Mg and micronutrients, might potentially constrain the productivity of crop under intensive chemical fertilization.
Syldie Bizimana
African Journal of Agricultural Research, Volume 12, pp 1362-1378; https://doi.org/10.5897/ajar2016.11786

Abstract:
In the African Great Lakes Region, bananas are grown on a diversity of soils with different weathering stages. However studies using the crop yield potential as a mean of soil weathering degree assessment are still scanty. Bananas were grown on five soils types to test if such a relationship could be ascertained. Mineralogical composition, elemental total analysis, routine chemical analysis, oxalates and dithionite-citrate-bicarbonate (DCB) extractions on the 0-20 and 20-40 cm soil layers were used as soil characteristics. Banana yield was higher in Cibitoke where the soil was characterized with relatively high values of total reserves in bases (TRB) and the weathering index of Parker (WIP). In contrast, no yield was recorded in Gitega where the soil had relatively lower values of TRB and WIP and high Fe DCB/Fe total ratio. Furthermore, banana yield was strongly and significantly (p<0.05) correlated with the TRB, the mineral reserves, Fe oxalate/Fe DCB ratio, the silt content and poorly correlated with the soil pH, total carbon and nitrogen, available P, exchangeable bases and the CEC. It was concluded that banana yield potential reflected well the soil weathering extent and in complement to soil properties related the routine analysis, the total analysis provide even more precision to elucidate the snapshot of the soil properties in the light of the observed banana yield potential. Key words: Banana, yield potential, correlation, routine analysis, soil weathering indices, total analysis.
, G.U. Chibuike, S. Peth, Y. Ouyang
Environmental Monitoring and Assessment, Volume 189; https://doi.org/10.1007/s10661-017-5881-y

Abstract:
Soil organic matter (SOM) is known to play vital roles in the maintenance and improvement of many soil properties and processes. These roles, which largely influence soil functions, are a pool of specific contributions of different components of SOM. The soil functions, in turn, normally define the level of soil degradation, viewed as quantifiable temporal changes in a soil that impairs its quality. This paper aims at providing a generalized assessment of the current state of knowledge on the usefulness of SOM in monitoring soil degradation, based on its influence on the physical, chemical and biological properties and processes of soils. Emphasis is placed particularly on the effect of SOM on soil structure and availability of plant nutrients. Although these properties are discussed separately, the soil system is of dynamic and interactive nature, and changes in one property will likely affect other soil properties as well. Thus, functions of SOM almost always affect various soil properties and processes and engage in multiple reactions. In view of its role in soil aggregation and erosion control, in availability of plant nutrients and in ameliorating other forms of soil degradation than erosion, SOM has proven to be an important indicator of soil degradation. It has been suggested, however, that rather than the absolute amount, temporal change and potential amount of SOM be considered in its use as indicator of soil degradation, and that SOM may not be an all-purpose indicator. Whilst SOM remains a candidate without substitute as long as a one-parameter indicator of soil degradation is needed, narrowing down to the use of its labile and microbial components could be more appropriate, since early detection is important in the control and management of soil degradation.
Published: 1 January 2017
Science of The Total Environment, Volume 575, pp 564-572; https://doi.org/10.1016/j.scitotenv.2016.09.018

Abstract:
The intensification of grassland management by nitrogen (N) fertilization and irrigation may threaten the future integrity of fragile semi-arid steppe ecosystems by affecting the concentrations of base cation and micronutrient in soils. We extracted base cations of exchangeable calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) and extractable micronutrients of iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) from three soil aggregate sizes classes (microaggregates, 2mm) from a 9-yearN and water field manipulation study. There were significantly more base cations (but not micronutrients) in microaggregates compared to macroaggregates which was related to greater soil organic matter and clay contents. Nitrogen addition significantly decreased exchangeable Ca by up to 33% in large and small macroaggregates and exchangeable Mg by up to 27% in three aggregates but significantly increased extractable Fe, Mn and Cu concentrations (by up to 262%, 150%, and 55%, respectively) in all aggregate size classes. However, water addition only increased exchangeable Na, while available Fe and Mn were decreased by water addition when averaging across all N treatments and aggregate classes. The loss of exchangeable Ca and Mg under N addition and extractable Fe and Mn in soil aggregates under water addition might potentially constrain the productivity of this semi-arid grassland ecosystem.
Jinfei Yin, , Heyong Liu, Xue Feng, Zhuwen Xu,
Published: 23 November 2016
Solid Earth, Volume 7, pp 1565-1575; https://doi.org/10.5194/se-7-1565-2016

Abstract:
Ongoing increases in anthropogenic nitrogen (N) inputs have largely affected soil carbon (C) and nutrient cycling in most terrestrial ecosystems. Numerous studies have concerned the effects of elevated N inputs on soil dissolved organic carbon (DOC), dissolved inorganic N (DIN), available phosphorus (AP), exchangeable calcium (Ca) and magnesium (Mg), and available iron (Fe) and manganese (Mn). However, few have emphasized the stoichiometric traits of these soil parameters, especially within different soil aggregate fractions. In a semiarid grassland of Inner Mongolia, we studied the effect of N addition on the ratios of DOC : DIN, DOC : AP, DIN : AP, exchangeable Ca : Mg, available Fe : Mn within three soil aggregate classes of large macroaggregates (> 2000 µm), small macroaggregates (250–2000 µm), and microaggregates (< 250 µm). Elevated N inputs significantly decreased the DOC : DIN ratio within three soil aggregates. The soil DOC : AP ratio significantly decreased along with increasing N gradients within large macroaggregates and microaggregates. Nitrogen significantly decreased the ratio of exchangeable Ca : Mg within soil macroaggregates. The ratio of available Fe : Mn decreased with N addition within three soil aggregate classes. Alteration of elemental stoichiometry within soil fractions that are characterized by different nutrient retention capacity will influence the chemical composition of soil microorganisms and plant quality.
, Timothy E. Smith, Bruce Hogg, Scott Swift, Luke Verstraten, Philippa Bryant, Bernhard J. Wehr, Neil Tindale, ,
Published: 1 June 2016
Forest Ecology and Management, Volume 370, pp 65-75; https://doi.org/10.1016/j.foreco.2016.03.058

Abstract:
Land-use change can have a major influence on soil organic carbon (SOC) and above-ground C pools. We assessed a change from native vegetation to introduced Pinus species plantations on C pools using eight paired sites. At each site we determined the impacts on 0–50 cm below-ground (SOC, charcoal C, organic matter C, particulate organic C, humic organic C, resistant organic C) and above-ground (litter, coarse woody debris, standing trees and woody understorey plants) C pools. In an analysis across the different study sites there was no significant difference (P > 0.05) in SOC or above-ground tree C stocks between paired native vegetation and pine plantations, although significant differences did exist at specific sites. SOC (calculated based on an equivalent soil mass basis) was higher in the pine plantations at two sites, higher in the native vegetation at two sites and did not differ for the other four sites. The site to site variation in SOC across the landscape was far greater than the variation observed with a change from native vegetation to introduced Pinus plantation. Differences between sites were not explained by soil type, although tree basal area was positively correlated with 0–50 cm SOC. In fact, in the native vegetation there was a significant linear relationship between above-ground biomass and SOC that explained 88.8% of the variation in the data. Fine litter C (0–25 mm diameter) tended to be higher in the pine forest than in the adjacent native vegetation and was significantly higher in the pine forest at five of the eight paired sites. Total litter C (0–100 mm diameter) increased significantly with plantation age (R2 = 0.64). Carbon stored in understorey woody plants (2.5–10 cm DBH) was higher in the native vegetation than in the adjacent pine forest. Total site C varied greatly across the study area from 58.8 Mg ha−1 at a native heathland site to 497.8 Mg ha−1 at a native eucalypt forest site. Our findings suggest that the effects of change from native vegetation to introduced Pinus sp. forest are highly site-specific and may be positive, negative, or have no influence on various C pools, depending on local site characteristics (e.g. plantation age and type of native vegetation).
Linyou Lü, , Heyong Liu, Jinfei Yin, Jiangtao Xiao, Zhengwen Wang, Yan Zhao, Guoqing Yu, ,
Published: 12 April 2016
Solid Earth, Volume 7, pp 549-556; https://doi.org/10.5194/se-7-549-2016

Abstract:
Soil coarseness is the main process decreasing soil organic matter and threatening the productivity of sandy grasslands. Previous studies demonstrated negative effect of soil coarseness on soil carbon storage, but less is known about how soil base cations (exchangeable Ca, Mg, K, and Na) and available micronutrients (available Fe, Mn, Cu, and Zn) response to soil coarseness. In a semi-arid grassland of Northern China, a field experiment was initiated in 2011 to mimic the effect of soil coarseness on soil base cations and available micronutrients by mixing soil with different mass proportions of sand: 0 % coarse elements (C0), 10 % (C10), 30 % (C30), 50 % (C50), and 70 % (C70). Soil coarseness significantly increased soil pH in three soil depths of 0–10, 10–20 and 20–40 cm with the highest pH values detected in C50 and C70 treatments. Soil fine particles (smaller than 0.25 mm) significantly decreased with the degree of soil coarseness. Exchangeable Ca and Mg concentrations significantly decreased with soil coarseness degree by up to 29.8 % (in C70) and 47.5 % (in C70), respectively, across three soil depths. Soil available Fe, Mn, and Cu significantly decreased with soil coarseness degree by 62.5, 45.4, and 44.4 %, respectively. As affected by soil coarseness, the increase of soil pH, decrease of soil fine particles (including clay), and decline in soil organic matter were the main driving factors for the decrease of exchangeable base cations (except K) and available micronutrients (except Zn) through soil profile. Developed under soil coarseness, the loss and redistribution of base cations and available micronutrients along soil depths might pose a threat to ecosystem productivity of this sandy grassland.
Davi Lopes Do Carmo, Laís Botelho De Lima,
Published: 1 January 2016
by SciELO
Revista Brasileira de Ciência do Solo, Volume 40; https://doi.org/10.1590/18069657rbcs20150152

Abstract:
The composition of organic waste (OW) and its effect on soil processes may change soil fertility and electrical conductivity (EC). The side effects of waste use in crop fertilization are poorly understood for Brazilian soils. This study examined the effect of the addition of 15 different organic wastes to Oxisols and a Neosol on pH, base saturation, EC, cation exchange capacity (CEC at pH 7), and the availability of Al, macro (P, K, Ca2+, Mg2+ and S) and micronutrients (B, Fe2+, Mn2+, Cu2+ and Zn2+). Soil samples (150 g) were treated with chicken, pig, horse, cattle, and quail manures, sewage sludge 1 and 2, eucalyptus sawdust, plant substrate, coconut fiber, pine bark, coffee husk, peat, limed compost, and biochar. Wastes were added considering a fixed amount of C (2 g kg-1), which resulted in waste rates ranging from 2.5 to 25.6 Mg ha-1. The soil-waste mixtures were incubated for 330 days in laboratory conditions. The waste liming or acidification values were soil-dependent. The use of some manures and compost increased the pH to levels above of those considered adequate for plant growth. The soil EC was slightly increased in the Neosol and in the medium textured Oxisol, but it was sharply changed (from 195 to 394 µS cm-1) by the addition of organic wastes in the clayey Oxisol, although the EC values were below the range considered safe for plant growth. Changes in the soil availability of P, K+, Ca2+ and Zn2+ were highly related to the inputs of these nutrients by the wastes, and other factors in soil changed due to waste use. Organic waste use simultaneously affects different soil fertility attributes; thus, in addition to the target nutrient added to the soil, the soil acidity buffering capacity and the waste liming and agronomic value must be taken into account in the waste rate definition
Published: 1 January 2016
Tropical Forestry Handbook pp 93-283; https://doi.org/10.1007/978-3-642-54601-3_96

Abstract:
The subject geology and soils is fundamental for tropical forest management. This chapter is divided into three logical parts: The first describes soil-forming factors and processes. The second provides the exhaustive description of definition, properties of different soil types, and their use for forest purposes. The following soil groups are dealt with: Mature Soils of the Humid and Subhumid Tropics, Representative Soils of the Semiarid and Arid Tropics, Soils Mainly Conditioned by Parent Material and Topography, Temporarily or Permanently Hydromorphic Soils, Soils of the Steppes, and finally Tropical Soils Conditioned by Human Influence. The third part deals with the organization and management of soil surveys; this allows the forest manager to project necessary soil surveys.
Published: 17 October 2015
Tropical Forestry Handbook pp 1-191; https://doi.org/10.1007/978-3-642-41554-8_96-1

Abstract:
The subject geology and soils is fundamental for tropical forest management. This chapter is divided into three logical parts: The first describes soil-forming factors and processes. The second provides the exhaustive description of definition, properties of different soil types, and their use for forest purposes. The following soil groups are dealt with: Mature Soils of the Humid and Subhumid Tropics, Representative Soils of the Semiarid and Arid Tropics, Soils Mainly Conditioned by Parent Material and Topography, Temporarily or Permanently Hydromorphic Soils, Soils of the Steppes, and finally Tropical Soils Conditioned by Human Influence. The third part deals with the organization and management of soil surveys; this allows the forest manager to project necessary soil surveys.
, Jamshid Ashigh, Manoj K. Shukla, Russ Perkins
Published: 7 May 2015
Abstract:
Indaziflam, a broad-spectrum, pre-emergence herbicide was the focus of a field investigation conducted after the identification of sporadic injury symptoms on the pecan trees a few months after the application. The study was conducted in two pecan orchards located in southern New Mexico, USA, and southeastern Arizona, USA. The objectives of this study were to evaluate the occurrence and distribution of indaziflam in the soil profile of areas where pecan trees were injured (impacted) and areas where no injury symptoms were observed (unimpacted), and to determine the relationship between indaziflam concentrations and soil properties in those locations. Soil samples were collected, one year after applications, from six depth representing 0–7, 7–15, 15–30, 30–60, 60–90 and 90–120 cm depth to determine the concentration of indaziflam in impacted and unimpacted areas of the two orchards. Soil samples were analyzed to determine texture, bulk density, organic matter content, cation exchange capacity, pH, nitrate, chloride and calcium concentrations. The detection frequency of indaziflam was higher in Arizona than in New Mexico, likely due to the differences between the tillage practices and sand contents of the orchards. No significant correlations were observed between indaziflam and soil properties, however indaziflam was mostly detected in areas where pecan trees were unimpacted probably as result of greater organic matter content and soil porosity. More research is needed to understand the causes of injury to pecan trees by indaziflam application.
Yuge Zhang, Shan Yang, Mingming Fu, Jiangping Cai, Yongyong Zhang, , , Yongfei Bai,
Published: 19 February 2015
Journal of Arid Land, Volume 7, pp 361-369; https://doi.org/10.1007/s40333-015-0004-5

Abstract:
The long-term productivity of a soil is greatly influenced by cation exchange capacity (CEC). Moreover, interactions between dominant base cations and other nutrients are important for the health and stability of grassland ecosystems. Soil exchangeable base cations and cation ratios were examined in a 11-year experiment with sheep manure application rates 0–1,500 g/(m2·a) in a semi-arid steppe in Inner Mongolia of China, aiming to clarify the relationships of base cations with soil pH, buffer capacity and fertility. Results showed that CEC and contents of exchangeable calcium (Ca2+), magnesium (Mg2+), potassium (K+) and sodium (Na+) were significantly increased, and Ca2+ saturation tended to decrease, while K+ saturation tended to increase with the increases of sheep manure application rates. The Ca2+/Mg2+ and Ca2+/K+ ratios decreased, while Mg2+, K+ and Na+ saturations increased with increasing manure application rates. Both base cations and CEC were significantly and positively correlated with soil organic carbon (SOC) and soil pH. The increases of SOC and soil pH would be the dominant factors that contribute to the increase of cations in soil. On a comparison with the initial soil pH before the experiment, we deduced that sheep manure application could partly buffer soil pH decrease potentially induced by atmospheric deposition of nitrogen and sulfur. Our results indicate that sheep manure application is beneficial to the maintenance of base cations and the buffering of soil acidification, and therefore can improve soil fertility in the semi-arid steppes of northeastern China.
, Annette Teltewskoi, Claudia Fiencke, ,
Published: 2 October 2014
Biodegradation, Volume 122, pp 211-227; https://doi.org/10.1007/s10533-014-0037-4

Abstract:
Plant growth in arctic tundra is known to be commonly limited by nitrogen. However, biogeochemical interactions between soil, vegetation and microbial biomass in arctic ecosystems are still insufficiently understood. In this study, we investigated different compartments of the soil-vegetation system of polygonal lowland tundra: bulk soil, inorganic nutrients, microbial biomass and vegetation biomass were analyzed for their contents of carbon, nitrogen, phosphorus and potassium. Samples were taken in August 2011 in the Indigirka lowlands (NE Siberia, Russia) in a detailed grid (4 m × 5 m) in one single ice-wedge polygon. We used a stoichiometric approach, based on the N/P ratios in the vegetation biomass and the investigated soil fractions, to analyze limitation relations in the soil-vegetation system. Plant growth in the investigated polygonal tundra appears to be co-limited by nitrogen and phosphorus or in some cases only limited by nitrogen whereas potassium is not limiting plant growth. However, as the N/P ratios of the microbial biomass in the uppermost soil horizons were more than twice as high as previously reported for arctic ecosystems, nitrogen mineralization and fixation may be limited at present by phosphorus. We found that only 5 % of the total nitrogen is already cycling in the biologically active fractions. On the other hand, up to 40 % of the total phosphorus was found in the biologically active fractions. Thus, there is less potential for increased phosphorus mineralization than for increased nitrogen mineralization in response to climate warming, and strict phosphorus limitation might be possible in the long-term.
Kaihua Liao, Shaohui Xu, Jichun Wu, , Lesheng An
Journal of Plant Nutrition and Soil Science, Volume 177, pp 775-782; https://doi.org/10.1002/jpln.201300176

Abstract:
Agricultural, environmental and ecological modeling requires soil cation exchange capacity (CEC) that is difficult to measure. Pedotransfer functions (PTFs) are thus routinely applied to predict CEC from easily measured physicochemical properties (e.g., texture, soil organic matter, pH). This study developed the support vector machines (SVM)-based PTFs to predict soil CEC based on 208 soil samples collected from A and B horizons in Qingdao City, Shandong Province, China. The database was randomly split into calibration and validation datasets in proportions of 3:1 using the bootstrap method. The optimal SVM parameters were searched by applying the genetic algorithm (GA). The performance of SVM models was compared to those of multiple stepwise regression (MSR) and artificial neural network (ANN) models. Results show that the accuracy of CEC predicted by SVM improves considerably over those predicted by MSR and ANN. The performance of SVM for B horizon (R2 = 0.85) is slightly better than that for A horizon (R2 = 0.81). The SVM is a powerful approach in the simulation of nonlinear relationship between CEC and physicochemical properties of widely distributed samples from different soil horizons. Sensitivity analysis was also conducted to explore the influence of each input parameter on the CEC predictions by SVM. The clay content is the most sensitive parameter, followed by soil organic matter and pH, while sand content has the weakest influence. This suggests that clay is the most important predictor for predicting CEC of both soil horizons.
, M. Xu, M. Fan, S. S. Malhi, , ,
Canadian Journal of Soil Science, Volume 94, pp 281-294; https://doi.org/10.4141/cjss2013-012

Abstract:
Feng, W., Xu, M., Fan, M., Malhi, S. S., Schoenau, J. J., Six, J. and Plante, A. F. 2014. Testing for soil carbon saturation behavior in agricultural soils receiving long-term manure amendments. Can. J. Soil Sci. 94: 281–294. Agricultural soils are typically depleted in soil organic matter compared with their undisturbed counterparts, thus reducing their fertility. Organic amendments, particularly manures, provide the opportunity to restore soil organic matter stocks, improve soil fertility and potentially sequester atmospheric carbon (C). The application of the soil C saturation theory can help identify soils with large C storage potentials. The goal of this study was to test whether soil C saturation can be observed in various soil types in agricultural ecosystems receiving long-term manure amendments. Seven long-term agricultural field experiments from China and Canada were selected for this study. Manure amendments increased C concentrations in bulk soil, particulate organic matter+sand, and silt+clay fractions in all the experiments. The increase in C concentrations of silt+clay did not fit the asymptotic regression as a function of C inputs better than the linear regression, indicating that silt+clay did not exhibit C saturation behavior. However, 44% of calculated C loading values for silt+clay were greater than the presumed maximal C loading, suggesting that this maximum may be greater than 1 mg C m−2 for many soils. The influences of soil mineral surface properties on C concentrations of silt+clay fractions were site specific. Fine soil particles did not exhibit C saturation behavior likely because current C inputs were insufficient to fill the large C saturation deficits of intensely cultivated soils, suggesting these soils may continue to act as sinks for atmospheric C.
Published: 7 January 2014
Biogeochemistry, Volume 118, pp 413-442; https://doi.org/10.1007/s10533-013-9941-2

Abstract:
Using nutrient budgets, it has been proven that atmospheric deposition of Mg and Ca sustains the fertility of forest ecosystems on base-poor soils. However the fate of this nutrient input within the ecosystem was presently unknown. Our hypothesis is that the biological cycling of these nutrients is very rapid and conservative to prevent further Mg and Ca losses most especially in ecosystems on base-poor soils. Stable isotopes of magnesium and calcium (26Mg and 44Ca) were used to trace the dynamics of throughfall Mg and Ca in the forest soil of a 35-year-old beech stand. The aim of the present study was to (1) understand the processes and the velocity of the incorporation of tracers in the biogeochemical cycles and (2) compute Mg and Ca budgets for the ecosystem by isotope dilution. Rainfall Mg and Ca were strongly and rapidly retained mainly by ion exchange in the thin OL litter-layer. However, Ca was much more strongly retained in the litter-layer than Mg. As a result, 2 years after the application of tracers (2012), 92 % of 26Mg and 67 % of 44Ca was released and transferred to the soil or taken up by trees. The vertical transfer of Mg was very slow only 15 % of 26Mg was found below 15 cm depth in 2012. Ca was slower than 26Mg only 9 % of 44Ca was found below 5 cm depth. Although matrix flow was the main vertical transfer process of Ca and Mg, preferential transfer in macropores occurred. Overall, Mg was more rapidly leached through the soil profile than Ca because the soil CEC was mainly composed of organic charges which affinity for Ca is much higher than for Mg. 27 % of 26Mg and 20 % of 44Ca was found in tree biomass and total tracer recovery was close to 100 %. These results suggest that no tracers were lost to drainage over the 2 years. Finally, applying the isotopic dilution theory to the whole-ecosystem enabled us to estimate Mg and Ca budgets −0.9 kg ha−1 year−1 for Mg, which was close to computed input–output budgets −0.8 and 0 kg ha−1 year−1 for Ca, which was very different from input–output budgets (−3.1 kg ha−1 year−1). Our results suggest that a Ca source is underestimated or not taken into account. Over all, organic matter of the litter-layer and in the soil profile played an essential role in the retention of throughfall Mg and Ca and their cycling within the forest ecosystem.
Ángel Faz, , M. Ángeles Muñoz,
Published: 9 November 2013
Environmental Earth Sciences, Volume 71, pp 5027-5036; https://doi.org/10.1007/s12665-013-2894-x

Abstract:
Topsoil and subsoil samples located adjacent and distant from the mining operations sites were collected. Most total metals showed no significant differences between topsoil and subsoil or proximity, suggesting that they derive from endogenous parent material. There was an increment in Hg in topsoils adjacent to the mining operation sites, indicating a deposition of Hg from the amalgamation areas. Higher values of total, extractable and soluble As were observed adjacent to the mining operation sites, probably related to the presence of residues, rich in arsenopyrite. Organic matter and clay contents control the concentrations of EDTA-extractable Cd and Zn, while soil acidity was associated with the behaviour of As, Hg and Cu. In contrast the concentration of EDTA-extractable Pb was directly affected by its total concentration. In general, soluble metals were highly independent, without significant correlations with any soil physical and chemical properties.
S. E. Obalum, Y. Watanabe, C. A. Igwe, M. E. Obi, T. Wakatsuki
Communications in Soil Science and Plant Analysis, Volume 44, pp 1831-1848; https://doi.org/10.1080/00103624.2013.790401

Abstract:
The roles of fine-earth materials in the cation exchange capacity (CEC) of especially homogenous units of the kaolinitic and oxyhydroxidic tropical soils are still unclear. The CEC (pH 7) of some coarse-textured soils from southeastern Nigeria were related to their total sand, coarse sand (CS), fine sand (FS), silt, clay, and organic-matter (OM) contents before and after partitioning the dataset into topsoils and subsoils and into very-low-, low-, and moderate-/high-stability soils. The soil-layer categories showed similar CEC values; the stability categories did not. The CEC increased with decreasing CS but with increasing FS. Silt correlated negatively with the CEC, except in the moderate- to high-stability soils. Conversely, clay and OM generally impacted positively on the CEC. The best-fitting linear CEC function (R2, 68%) was attained with FS, clay, and OM with relative contributions of 26, 38, and 36%, respectively. However, more reliable models were attained after partitioning by soil layer (R2, 71–76%) and by soil stability (R2, 81–86%). Notably FS's contribution to CEC increased while clay's decreased with increasing soil stability. Clay alone satisfactorily modeled the CEC for the very-low-stability soils, whereas silt contributed more than OM to the CEC of the moderate- to high-stability soils. These results provide new evidence about the cation exchange behavior of FS, silt, and clay in structurally contrasting tropical soils.
, Naresh V. Thevathasan
Communications in Soil Science and Plant Analysis, Volume 44, pp 1733-1748; https://doi.org/10.1080/00103624.2013.769563

Abstract:
Despite significant evidence that green manures from agroforestry species can improve soil fertility, green biomasses from many agroforestry species have not been sufficiently explored. In this study, we determined the suitability of green manures of Tithonia diversifolia, Gliricidia sepium, and Senna spectabilis for smallholder agriculture in Africa. Field trials were established to compare them with mineral fertilizer. The results showed that green manures of the three species were of high quality based on their macronutrient compositions. The effect of the green manures (particularly Tithonia) on both the biomass and fruit yield of okro were comparable and in some cases greater than fertilizer treatments. Total yield response in Tithonia treatment was 61% and 20% greater than the control and fertilizer treatments, respectively. In addition, the okro plants recovered a greater percentage of the nitrogen (N), phosphorus (P), and potassium (K) added as green manure compared to fertilizer-treated plots, which received the greatest N, P, and K inputs.
Published: 4 December 2012
Journal of Arid Land, Volume 5, pp 42-50; https://doi.org/10.1007/s40333-013-0140-8

Abstract:
As a pioneer leguminous shrub species for vegetation re-establishment, Caragana microphylla is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region, North China. C. microphylla plantations modify organic carbon (SOC), nitrogen (N) and phosphorus dynamics, bulk density and water-holding capacity, and biological activities in soils, but little is known with regard to soil exchange properties. Variation in soil exchangeable base cations was examined under C. microphylla plantations with an age sequence of 0, 5, 10, and 22 years in the Horqin Sandy Land, and at the depth of 0–10, 10–20, and 20–30 cm, respectively. C. microphylla has been planted on the non-vegetated sand dunes with similar physical-chemical soil properties. The results showed that exchangeable calcium (Ca), magnesium (Mg), and potassium (K), and cation exchange capacity (CEC) were significantly increased, and Ca saturation tended to decrease, while Mg and K saturations were increased with the plantation years. No difference was observed for exchangeable sodium (Na) neither with plantation years nor at soil depths. Of all the base cations and soil layers, exchangeable K at the depth of 0–10 cm accumulated most quickly, and it increased by 1.76, 3.16, and 4.25 times, respectively after C. microphylla was planted for 5, 10, and 22 years. Exchangeable Ca, Mg, and K, and CEC were significantly (P<0.001) and positively correlated with SOC, total N, pH, and electrical conductivity (EC). Soil pH and SOC are regarded as the main factors influencing the variation in exchangeable cations, and the preferential absorption of cations by plants and different leaching rates of base cations that modify cation saturations under C. microphylla plantation. It is concluded that as a nitrogen-fixation species, C. microphylla plantation is beneficial to increasing exchangeable base cations and CEC in soils, and therefore can improve soil fertility and create favorable microenvironments for plants and creatures in the semi-arid sandy land ecosystems.
Revista Brasileira de Ciência do Solo, Volume 36, pp 909-920; https://doi.org/10.1590/s0100-06832012000300021

Abstract:
O sistema plantio direto (SPD), em função de seu tempo de estabelecimento, pode promover aumento na quantidade de resíduos vegetais adicionados à superfície do solo e, consequentemente, modificações nos seus atributos químicos e físicos. O trabalho teve por objetivo quantificar a deposição de resíduos vegetais na superfície do solo (RVS) e as modificações nos teores de matéria orgânica leve (MOL), nos estoques de carbono e nitrogênio, nos teores de fósforo remanescente (Prem) e nos atributos físicos do solo - densidade de partículas (Dp), densidade do solo (Ds) e volume total de poros (VTP) -, bem como avaliar a origem do carbono por meio de técnicas isotópicas (13C). Para isso, em Montividiu (GO) foram selecionadas áreas sob SPD com diferentes tempos de implantação: SPD com três anos de implantação (SPD3), SPD com 15 anos de implantação (SPD15) e SPD com 20 anos de implantação (SPD20), as quais foram comparadas a uma área de Cerrado nativo stricto sensu (CE) e a uma área de pastagem plantada de Brachiaria decumbens (PA). Em cada uma das áreas, foram coletadas amostras nas profundidades de 0-5, 5-10 e 10-20 cm. O solo das áreas de estudo foi classificado como Latossolo Vermelho distroférrico. O delineamento utilizado foi inteiramente casualizado. Foi observado aumento nos teores de RVS, MOL, VTP, Prem, C e N em função do tempo de implantação do SPD. A área de SPD com 20 anos apresentou maiores valores de C e N e valores semelhantes de Ds e MOL, em relação ao CE. As análises de 13C demonstraram que as leguminosas estão contribuindo de forma significativa para a composição da matéria orgância nas áreas sob SPD. Nas áreas sob SPD, verificou-se aumento dos valores de estoque de C e de N em função do tempo de implantação em todas as profundidades analisadas; as áreas SPD15 e SPD20 apresentaram nas camadas superficiais valores semelhantes e, ou, superiores aos da área de CE. A área de PA apresentou os piores valores dos atributos analisados, demonstrando estar em estádio mais avançado de degradação.
, I. González, L.A. García-De la Rosa, F. Mancilla-Peña,
Journal of Environmental Management, Volume 92, pp 448-456; https://doi.org/10.1016/j.jenvman.2010.08.033

Abstract:
Carbon paste electrodes (CPEs) modified with a biosolid, two types of soils with different amounts of organic matter (OM), and two biocomposites (soils mixed with a biosolid) were used to assess and compare the Cu(II) ion retention properties of the organic matter contained in the samples. The accumulation of Cu(II) on the surface of the modified carbon paste electrodes (MCPEs) was performed under open-circuit conditions. When comparing the response of the MCPEs while assessing parameters such as pH, preconcentration time, and adsorption/desorption capacity, it was found that the reaction mechanism of the two soils is different between the soils and dissimilar from the biosolid; while the biocomposites show reaction mechanisms that are intermediate between those of the soils and the biosolid. This was proven with the use of infrared spectroscopy, since the FTIR spectra show similarities between the two soils and significant differences between the soils and the biosolid.
Published: 15 November 2009
Journal of Hazardous Materials, Volume 171, pp 262-267; https://doi.org/10.1016/j.jhazmat.2009.05.137

Abstract:
The displacement of Ca2+, Mg2+, K+ and Al3+ from the A and Bw or Bt horizons of two soils developed over serpentinized amphibolites when equilibrated in Cu2+, Cd2+ or Pb2+ solutions was determined, together with the concomitant sorption of the heavy metal. The contributions of Mg2+ to the effective cation exchange capacities of the A and Bt horizons of the Endoleptic Luvisol were 57% and 94%, respectively, and its contributions to those of the A and Bw horizons of the Mollic Cambisol were 70% and 77%, respectively. In all four horizons, cation exchange, chiefly with Mg2+ and Ca2+, was the process chiefly responsible for sorption of Cd2+, Cu2+ and Pb2+. Al3+ and K+ were hardly implicated, especially in the case of Cd2+.
, , Patrick Ofori, Gabriel W. Quansah, ,
Soil Science Society of America Journal, Volume 73, pp 961-966; https://doi.org/10.2136/sssaj2008.0204

Abstract:
This study examined the influence of organic residue quality and N fertilizer on aggregate-associated soil organic matter (SOM) in maize (Zea mays L.) cropping systems of southern Ghana. Six residue treatments of differing quality [Crotalaria juncea L., Leucaena leucocephala (Lam.) de Wit, maize stover, sawdust, cattle manure, and a control with no residues added] were applied at 4 Mg C ha−1 yr−1 both with and without fertilizer N additions (120 kg N ha−1 season−1). Soils (0–15 cm) were sampled 3 yr after study implementation and wet sieved into four aggregate size classes (8000–2000, 2000–250, 250–53, and 250 μm), microaggregates within macroaggregates (53–250 μm), and macroaggregate-occluded silt and clay (<53 μm). Nitrogen fertilizer additions reduced aggregate stability, as was evident from a 40% increase in the weight of the silt and clay fraction (P = 0.014) as well as a decrease in microaggregates across all residue types (P = 0.019). Fertilizer similarly affected C and N storage within these aggregate fractions, while the effects of residue quality were largely insignificant. Our results suggest that fertilizer effects on soil aggregation may have important implications for long-term SOM dynamics. Copyright © 2009. Soil Science Society. Soil Science Society of America
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