Risk of municipal solid waste compost and sewage sludge use on photosynthetic performance in common crop (<Emphasis Type="Italic">Triticum durum</Emphasis>)

The effect of composted municipal solid waste (MSW) and sewage sludge (SS) on photosynthetic activity of wheat (Triticum durum L.) was investigated. Chlorophyll fluorescence and gas exchange parameters were assessed following application of up to 300 t ha^?1 of MSW compost or SS. 100 t ha^?1 MSW compost was optimal for the plant growth, which showed 78% stimulation as compared to the control. This was associated with higher maximum quantum efficiency (F _v /F _m) of photosystem II (PSII) and the actual quantum efficiency of PSII open centers at light adapted state (ΔF/\(F_{\rm m}^{\prime}\)). Maximal values of net photosynthetic rate and stomatal conductance were recorded at 100 t ha^?1 MSW compost (+40 and +116%, respectively). Ribulose bisphosphate carboxylase/oxygenase (RubisCO) activity was also significantly stimulated at 100 t ha^?1, while less significant impact was found in SS treatment. A marked accumulation of Ni, Pb, Cu, and Zn in concomitance with membrane lipid peroxidation were observed at 200–300 t ha^?1 MSW compost and SS, resulting in lower photosynthetic activity and altered PSII functional integrity. Altogether, these results suggest that the MSW compost at 100 t ha^?1 would be suitable for wheat cultivation, within the critical limits of heavy metal accumulation. However, long-term field experiments seem necessary to more accurately evaluate the safety of MSW application.     

Effects of forest liming on soil processes

On the basis of a field experiment in Norway spruce with acid irrigation and compensatory liming of the soil surface (Höglwald, S-Bavaria), liming effects are described as lime dissolution rate, transformation of carbonate buffer to exchange buffer, time required for deacidification of soil and drainage water, mobilization of Cu and Pb, changes in soil organisms, humus decomposition, and nitrogen turnover. It was shown that lime dissolution followed an exponentially decreasing curve. 4 t ha^-1 dolomitic lime were dissolved within 6 years. Additional acid irrigation of 4 kmol H⁺ ha^-1 yr^-1 as sulphuric acid speeded up the lime dissolution to about 4 years. After dissolution of lime about 70% of Ca and about 30% of Mg, both originating from lime dissolution, are retained in the surface humus layer, loading the exchange buffer capacity there. Liming acted as a protection against acid irrigation but the extension of soil deacidification downwards proceeded slowly due to the high base neutralizing capacity of protonated functional groups of the organic matter. The main depth effect is caused by Mg translocation. A significant increase of organic Cu complexes occurred due to mobilization of water soluble humus decomposition products. The effect of liming on litter decomposing organisms is demonstrated with microorganisms, collembolae and earthworms regarding the abundance and the structure of dominance. It was shown that liming may induce unusually large changes in biocenoses of forest soils. The decay of surface humus accounted for 7.2 t ha^-1 or 23% of the store within 7 years. Within the same time span, liming caused a loss of about 170 kg N ha^-1 or 14% of the store of the surface humus layer. The nitrate concentration in the drainage water thus increased by about 50 to 60 mg NO₃ ^- L^-1. Site-specific conditions are discussed, which produce such negative liming effects as increased nitrate concentration of seepage, humus decay and heavy metal mobilization. Redistribution of tree roots, induction of boron deficiency and root rot are also considered. It is indicated that liming may aggravate the increasing problem of nitrate contamination of forest ground water resources which is associated with deposition of atmogenous nitrogen compounds. Some recommendations are given regarding forest practice.     

Field‐scale soil property changes under switchgrass managed for bioenergy

The capacity of perennial grasses to affect change in soil properties is well documented but information on switchgrass (Panicum virgatum L.) managed for bioenergy is limited. An on‐farm study (10 fields) in North Dakota, South Dakota, and Nebraska was sampled before switchgrass establishment and after 5 years to determine changes in soil bulk density (SBD), pH, soil phosphorus (P), and equivalent mass soil organic carbon (SOC). Changes in SBD were largely constrained to near‐surface depths (0–0.05 m). SBD increased (0–0.05 m) at the Nebraska locations (mean=0.16 Mg m^?3), while most South Dakota and North Dakota locations showed declines in SBD (mean=?0.18 Mg m^?3; range=?0.42–0.07 Mg m^?3). Soil pH change was significant at five of the 10 locations at near surface depths (0–0.05 m), but absolute changes were modest (range=?0.67–0.44 pH units). Available P declined at all sites where it was measured (North Dakota and South Dakota locations). When summed across the surface 0.3 m depth, annual decreases in available P averaged 1.5 kg P ha^?1 yr^?1 (range=0.5–2.8 kg P ha^?1 yr^?1). Averaged across locations, equivalent mass SOC increased by 0.5 and 2.4 Mg C ha^?1 yr^?1 for the 2500 and 10 000 Mg ha^?1 soil masses, respectively. Results from this study underscore the contribution of switchgrass to affect soil property changes, though considerable variation in soil properties exists within and across locations.     

Integrated effects of organic,inorganic and biological amendments on methane emission,soil quality and rice productivity in irrigated paddy ecosystem of Bangladesh: field study of two consecutive rice growing seasons

Aims

Effects of different soil amendments were investigated on methane (CH₄) emission, soil quality parameters and rice productivity in irrigated paddy field of Bangladesh.

Methods

The experiment was laid out in a randomized complete block design with five treatments and three replications. The experimental treatments were urea (220 kg ha^?1) + rice straw compost (2 t ha^?1) as a control, urea (170 kg ha^?1) + rice straw compost (2 t ha^?1) + silicate fertilizer, urea (170 kg ha^?1) + sesbania biomass (2 t ha^?1 ) + silicate fertilizer, urea (170 kg ha^?1) + azolla biomass (2 t ha^?1) + cyanobacterial mixture 15 kg ha^?1 silicate fertilizer, urea (170 kg ha^?1) + cattle manure compost (2 t ha^?1) + silicate fertilizer.

Results

The average of two growing seasons CH₄ flux 132 kg ha^?1 was recorded from the conventional urea (220 kg ha^?1) with rice straw compost incorporated field plot followed by 126.7 (4 % reduction), 130.7 (1.5 % reduction), 116 (12 % reduction) and 126 (5 % reduction) kg CH₄ flux ha^?1 respectively, with rice straw compost, sesbania biomass, azolla anabaena and cattle manure compost in combination urea and silicate fertilizer applied plots. Rice grain yield was increased by 15 % and 10 % over the control (4.95 Mg ha^?1) with silicate plus composted cattle manure and silicate plus azolla anabaena, respectively. Soil quality parameters such as soil organic carbon, total nitrogen, microbial biomass carbon, soil redox status and cations exchange capacity were improved with the added organic materials and azolla biofertilizer amendments with silicate slag and optimum urea application (170 kg ha^?1) in paddy field.

Conclusion

Integrated application of silicate fertilizer, well composted organic manures and azolla biofertilizer could be an effective strategy to minimize the use of conventional urea fertilizer, reducing CH₄ emissions, improving soil quality parameters and increasing rice productivity in subtropical countries like Bangladesh.     

The Effect of Compost Treatments and A Plant Cover with Agrostis tenuis on the Immobilization/Mobilization of Trace Elements in a Mine-Contaminated Soil

A semi-field experiment was conducted to evaluate the use of mixed municipal solid waste compost (MMSWC) and green waste-derived compost (GWC) as immobilizing agents in aided-phytostabilization of a highly acidic soil contaminated with trace elements, with and without a plant cover of Agrostis tenuis. The compost application ratio was 50 Mg ha^–1, and GWC amended soil was additionally limed and supplemented with mineral fertilizers.Both treatments had an equivalent capacity to raise soil organic matter and pH, without a significant increase in soil salinity and in pseudo-total As, Cu, Pb, and Zn concentrations, allowing the establishment of a plant cover. Effective bioavailable Cu and Zn decreased as a consequence of both compost treatments, while effective bioavailable As increased by more than twice but remained as a small fraction of its pseudo-total content. Amended soil had higher soil enzymatic activities, especially in the presence of plants.Accumulation factors for As, Cu, Pb, and Zn by A. tenuis were low, and their concentrations in the plant were lower than the maximum tolerable levels for cattle. As a consequence, the use of A. tenuis can be recommended for assisted phytostabilization of this type of mine soil, in combination with one of the compost treatments evaluated.     

The potential of Miscanthus to sequester carbon in soils: comparing field measurements in Carlow,Ireland to model predictions

Growing bioenergy crops such as Miscanthus has the potential to mitigate atmospheric carbon dioxide emissions by the replacement of fossil fuels and by storing carbon (C) in the soil due to land use change. Here we compare direct measurements of soil organic C fractions made in Carlow (Ireland) to model predictions made by RothC and a cohort model. Our results show that when Miscanthus is grown on land previously under arable agriculture, the soil organic C will increase to a level above that of native pasture, as Miscanthus organic material is shown to have a slow decomposition rate. In addition we demonstrate that for measured organic C, fractions of different lability are similar to the C pools used in RothC. Using the model predictions from RothC and Miscanthus yields from MISCANFOR, we predict that in Ireland, changing the land use from arable to Miscanthus plantations has the potential to store between 2 and 3 Mg C ha^?1 y^?1 depending on the crop yield and the initial soil organic C level.     

Municipal solid waste compost dose effects on soil microbial biomass determined by chloroform fumigation-extraction and DNA methods

We evaluated the relationship between microbial biomass C and N (B_C and B_N) as estimated by the chloroform fumigation-extraction (CFE) method and microbial biomass DNA concentration in a loam-clayey wheat cultivated soil. The soil received municipal solid waste compost at rates of 40 or 80 t ha^?1 and farmyard manure at 40 t ha^?1. Microbial biomasses C and N and DNA concentration centration showed the highest values for microorganisms counts with compost and farmyard manure at 40 t ha^?1. Compost applications at 40 t ha?1 improve the micro-organisms growth than that of 80 t ha^?1. Moreover a significant decrease of soil microbial biomass was noted after fertilisation for three years. The presence of humic acid and proteins impurities in DNA extracts; even in important level as in F-treated soil; did not affect the microbial biomass. The decrease of microbial biomass was due to heavy metals content elevation in compost at 80 t ha^?1 treated soil. Thus the highest rate of municipal solid waste compost induced the lowest ratio of biomass C to soil organic carbon and the lowest ratio of biomass N to soil organic nitrogen. There was a positive relationship between B_C, B_N and DNA concentration. DNA concentration was significantly and positively correlated with B_C and with B_N. However there was a negative correlation between either micro-organisms numbers and DNA concentration, or B_C and B_N. The comparison of the two used methods DNA extraction and CFE showed the lowest coefficient of variation (cv %) with DNA extraction method. This last method can be used as an alternative method to measure the microbial biomass in amended soils.     

Sorption and Desorption of Napropamide in Sandy Soil Amended with Chicken Dung and Palm Oil Mill Effluent

Beach Ridges Interspersed with Swales (BRIS) is a sandy soil and in Malaysia it is found exclusively in the east coast of Peninsular Malaysia. It is a marginal soil because of its low nutrient and water-holding capacity. However, with proper management and organic matter amendments some areas with BRIS soil are cultivated. Napropamide is a selective herbicide widely used to control weeds in BRIS soil. No previous studies have been reported on the effects of organic matter amendments on napropamide sorption in BRIS soil. This study was conducted to determine sorption and desorption of napropamide in BRIS soil amended with chicken dung (CD) and palm oil mill effluent (POME) at 0, 20, 40, and 80 Mg ha^?1. Potential interaction of dissolved organic carbon (DOC) with napropamide and their competition for sorption sites were also determined. Sorption isotherm data were fitted to the log-transformed Freundlich's equation. Sorption of napropamide was higher in soils amended with CD and POME as compared to non-amended soil. At the same rates of application, sorption was higher in soil amended with CD than POME. The Freundlich's coefficient (K_f) values were 0.22, 3.96, and 41.6 for nonamended soil, soil amended with 80 Mg ha^?1 POME, and soil amended with 80 Mg ha^?1 CD, respectively. Desorption of napropamide showed positive hysteresis and the hysteresis were greater with higher rates of CD and POME. There was no association between napropamide and DOC extracted from BRIS soil amended with either CD or POME and also there were no competitions between napropamide and DOC extracted from either CD or POME for sorption sites of the soil samples.     

Carbon Sequestration in Reclaimed Minesoils

Minesoils are drastically influenced by anthropogenic activities. They are characterized by low soil organic matter (SOM) content, low fertility, and poor physicochemical and biological properties, limiting their quality, capability, and functions. Reclamation of these soils has potential for resequestering some of the C lost and mitigating CO₂ emissions. Soil organic carbon (SOC) sequestration rates in minesoils are high in the first 20 to 30 years after reclamation in the top 15 cm soil depth. In general, higher rates of SOC sequestration are observed for minesoils under pasture and grassland management than under forest land use. Observed rates of SOC sequestration are 0.3 to 1.85 Mg C ha^{? 1} yr^{? 1} for pastures and rangelands, and 0.2 to 1.64 Mg C ha^{? 1} yr^{? 1} for forest land use. Proper reclamation and postreclamation management may enhance SOC sequestration and add to the economic value of the mined sites. Management practices that may enhance SOC sequestration include increasing vegetative cover by deep-rooted perennial vegetation and afforestation, improving soil fertility, and alleviation of physical, chemical and biological limitations by fertilizers and soil amendments such as biosolids, manure, coal combustion by-products, and mulches. Soil and water conservation are important to SOC sequestration. The potential of SOC sequestration in minesoils of the US is estimated to be 1.28 Tg C yr^?1, compared to the emissions from coal combustion of 506 Tg C yr^{? 1}.     

Effect of Vegetation Rehabilitation on Soil Carbon and Its Fractions in Mu Us Desert,Northwest China

Although vegetation rehabilitation on semi-arid and arid regions may enhance soil carbon sequestration, its effects on soil carbon fractions remain uncertain. We carried out a study after planting Artemisia ordosica (AO, 17 years), Astragalus mongolicum (AM, 5 years), and Salix psammophila (SP, 16 years) on shifting sand land (SL) in the Mu Us Desert, northwest China. We measured total soil carbon (TSC) and its components, soil inorganic carbon (SIC) and soil organic carbon (SOC), as well as the light and heavy fractions within soil organic carbon (LF-SOC and HF-SOC), under the SL and shrublands at depths of 100 cm. TSC stock under SL was 27.6 Mg ha^?1, and vegetation rehabilitation remarkably elevated it by 40.6 Mgha^?1, 4.5 Mgha^?1, and 14.1 Mgha^?1 under AO, AM and SP land, respectively. Among the newly formed TSC under the three shrublands, SIC, LF-SOC and HF-SOC accounted for 75.0%, 10.7% and 13.1% for AO, respectively; they made up 37.0%, 50.7% and 10.6% for AM, respectively; they occupied 68.6%, 18.8% and 10.0% for SP, respectively. The accumulation rates of TSC within 0–100 cm reached 238.6 g m^?2y^?1, 89.9 g m^?2y^?1 and 87.9 g m^?2y^?1 under AO, AM and SP land, respectively. The present study proved that the accumulation of SIC considerably contributed to soil carbon sequestration, and vegetation rehabilitation on shifting sand land has a great potential for soil carbon sequestration.     

Complexation of a Ligand with a Surfactant Micelle for Soil Heavy Metal Desorption

The ligands iodide (I^?) and thiocyanate (SCN^?), alone or in admixture, in combination with a non-ionic surfactant, Triton X-100, were evaluated as washing agents for heavy metal desorption from a contaminated soil. After seven successive washings, selective sequential extraction (SSE) was performed to determine the heavy metal content that remained associated with each geo-chemical fraction of the soil. The surfactant with 0.336 mol L^?1 of ligand I^? removed 75% Cd and 23% Cu, whereas the mobilization of Zn and Pb were not significant after 7 washings. At a concentration of 0.286 mol L^?1, the ligand SCN^? in the presence of surfactant removed 36% Cd, 44% Cu and 77% Zn. Among the washing agents, the combination of I^? and SCN^? produced the highest desorption efficiencies 95% Cd, 48% Cu, and 3.1% Pb, but not for Zn. The SCN^? ligand extracted the most Zn (77%). The SSE procedure indicated that the I^? removed metals from the exchangeable, carbonate and oxide fractions whereas SCN^? removed metals only from the exchangeable fraction. Both ligands, in the presence of surfactant, removed Cu from all fractions except the exchangeable sites, whereas only SCN^? plus surfactant removed Zn from all fractions. The ligand mixture plus surfactant mobilized only limited quantities of Pb from the oxide and residual fractions.     

Net changes of soil C stocks in two grassland soils 26 months after simulated pasture renovation including biochar addition

The use of deep‐rooting pasture species as a management practice can increase the allocation of plant carbon (C) below ground and enhance C storage. A 2‐year lysimeter trial was set up to compare changes in C stocks of soils under either deep‐ or shallow‐rooting pastures and investigate whether biochar addition below the top 10 cm could promote root growth at depth. For this i) soil ploughing at cultivation was simulated in a silt loam soil and in a sandy soil by inverting the 0 to 10 and 10‐ to 20‐cm‐depth soil layers, and a distinctive biochar (selected for each soil to overcome soil‐specific plant growth limitations) was mixed at 10 Mg ha^?1 in the buried layer, where appropriate and ii) three pasture types with contrasting root systems were grown. In the silt loam, soil inversion resulted in a general loss of C (2.0–8.1 Mg ha^?1), particularly in the buried horizon, under shallow‐rooting pastures only. The addition of a C‐rich biochar (equivalent to 7.6 Mg C ha^?1) to this soil resulted in a net C gain (21–40% over the non‐biochar treatment, P < 0.10) in the buried layer under all pastures; this overcame the loss of C in this horizon under shallow‐rooting pastures. In the sandy soil, all pastures were able to maintain soil C stocks at 10–20 cm depth over time, with minor gains of C (1.6–5.1 Mg ha^?1) for the profile. In this soil, the exposure of a skeletal‐ and nutrient‐depleted soil layer at the surface may have fostered root growth at depth. The addition of a nutrient‐rich biochar (equivalent to 3.6 Mg C ha^?1) to this soil had no apparent effect on C stocks. More research is needed to understand the mechanisms through which soil C stocks at depth are preserved.     

Influence of Matrix Composition on the Bioaccessibility of Copper,Zinc, and Nickel in Urban Residential Dust and Soil

This study examines factors affecting oral bioaccessibility of metals in household dust, in particular metal speciation, organic carbon content, and particle size, with the goal of addressing risk assessment information requirements. Investigation of copper (Cu) and zinc (Zn) speciation in two size fractions of dust (< 36 μ m and 80–150 μ m) using synchrotron X-ray absorption spectroscopy (XAS) indicates that the two metals are bound to different components of the dust: Cu is predominately associated with the organic phase of the dust, while Zn is predominately associated with the mineral fraction. Total and bioaccessible Cu, nickel (Ni), and Zn were determined (on dry weight basis) in the < 150 μ m size fraction of a set of archived indoor dust samples (n = 63) and corresponding garden soil samples (n = 66) from the City of Ottawa, Canada. The median bioaccessible Cu content is 66 μ g g^?1 in dust compared to 5 μ g g^?1 in soil; the median bioaccessible Ni content is 16 μ g g^?1 in dust compared to 2 μ g g^?1 in soil; and the median bioaccessible Zn content is 410 μ g g^?1 in dust compared to 18 μ g g^?1 in soil. For the same data set, the median total Cu content is 152 μ g g^?1 in dust compared to 17 μ g g^?1 in soil; the median total Ni content is 41 μ g g^?1 in dust compared to 13 μ g g^?1 in soil; and the median total Zn content is 626 μ g g^?1 in dust compared to 84 μ g g^?1 in soil. Organic carbon is elevated in indoor dust (median 28%) compared to soil (median 5%), and is a key factor controlling metal partitioning and therefore bioaccessibility. The results show that house dust and soil have distinct geochemical signatures and should not be treated as identical media in exposure and risk assessments. Separate measurements of the indoor and outdoor environment are essential to improve the accuracy of residential risk assessments.     

Short-term effects of thinning and liming on forest soils of pitch pine and Japanese larch plantations in central Korea

The influences of thinning (50% of standing density) and liming (Ca+Mg, 2 Mg ha⁻¹) on soil chemical properties were investigated for 2 years (2001, 2002) in 40-year-old pitch pine (Pinus rigida Mill.) and 44-year-old Japanese larch (Larix leptolepis Gord.) plantations established on similar soils. In general, soil properties varied significantly among plantations and treatments. For both plantations, thinning significantly increased soil organic C (SOC) concentrations whereas there were no significant changes in soil pH and Ca and Mg concentrations. In addition, thinning increased total soil N and Na concentrations for the pitch pine plantation and available P concentration for the Japanese larch plantation in the second year after the treatment. Liming did not affect soil chemical characteristics for the pitch pine plantation except for Na concentration. However, for the Japanese larch plantation, liming significantly increased soil pH and K, Ca and Mg concentrations and decreased SOC and total soil N concentrations. For both plantations, soil Al concentration did not change after thinning and liming and decreased exponentially with increased pH values. The increases in SOC and total soil N concentrations after thinning were possibly due to increases in decomposition of organic matter and root death. Although differences were not statistically significant, soil available P concentration tended to increase at early stages of liming for both plantations. These results suggested that thinning and liming seemed to regulate soil chemical properties for pitch pine and Japanese larch plantations established on similar soils.     

Long‐term impacts of manure amendments on carbon and greenhouse gas dynamics of rangelands

Livestock manure is applied to rangelands as an organic fertilizer to stimulate forage production, but the long‐term impacts of this practice on soil carbon (C) and greenhouse gas (GHG) dynamics are poorly known. We collected soil samples from manured and nonmanured fields on commercial dairies and found that manure amendments increased soil C stocks by 19.0 ± 7.3 Mg C ha^?1 and N stocks by 1.94 ± 0.63 Mg N ha^?1 compared to nonmanured fields (0–20 cm depth). Long‐term historical (1700–present) and future (present–2100) impacts of management on soil C and N dynamics, net primary productivity (NPP), and GHG emissions were modeled with DayCent. Modeled total soil C and N stocks increased with the onset of dairying. Nitrous oxide (N₂O) emissions also increased by ~2 kg N₂O‐N ha^?1 yr^?1. These emissions were proportional to total N additions and offset 75–100% of soil C sequestration. All fields were small net methane (CH₄) sinks, averaging ?4.7 ± 1.2 kg CH₄‐C ha^?1 yr^?1. Overall, manured fields were net GHG sinks between 1954 and 2011 (?0.74 ± 0.73 Mg CO₂ e ha^?1 yr^?1, CO₂e are carbon dioxide equivalents), whereas nonmanured fields varied around zero. Future soil C pools stabilized 40–60 years faster in manured fields than nonmanured fields, at which point manured fields were significantly larger sources than nonmanured fields (1.45 ± 0.52 Mg CO₂e ha^?1 yr^?1 and 0.51 ± 0.60 Mg CO₂e ha^?1 yr^?1, respectively). Modeling also revealed a large background loss of soil C from the passive soil pool associated with the shift from perennial to annual grasses, equivalent to 29.4 ± 1.47 Tg CO₂e in California between 1820 and 2011. Manure applications increased NPP and soil C storage, but plant community changes and GHG emissions decreased, and eventually eliminated, the net climate benefit of this practice.     

Calibration of the soil conditioning index (SCI) to soil organic carbon in the southeastern USA

Prediction of soil organic C sequestration with adoption of various conservation agricultural management approaches is needed to meet the emerging market for environmental services provided by agricultural land stewardship. The soil conditioning index (SCI) is a relatively simple model used by the USDA?CNatural Resources Conservation Service to predict qualitative changes in soil organic matter. Our objective was to develop a quantitative relationship between soil organic C derived from published field studies in the southeastern USA and SCI scores predicted from matching management conditions. We found that soil organic C sequestration (at 20?±?5 cm depth) could be reliably related to SCI across a diversity of studies in the region using the regression slope: 1.65 Mg C ha^?1 SCI^?1 [which translated into a rate of 0.25?±?0.04 Mg C ha^?1 yr^?1 SCI^?1 (mean±standard error of 31 slope estimates)]. The calibration of soil organic C on SCI scores will allow SCI to become a quantitative tool for natural resource professionals to predict soil organic C sequestration for farmers wanting to adopt conservation practices.     

Responses of maize grain yield to changes in acid soil characteristics after soil amendments

An experiment was conducted from 1997 to 2000 on an acid soil in Cameroon to assess the effectiveness of cultivating acid tolerant maize (Zea mays L.) cultivar and the use of organic and inorganic fertilizers as options for the management of soil acidity. The factors investigated were: phosphorus (0 and 60 kg ha^?1), dolomitic lime (0 and 2 t ha^?1), organic manure (no manure, 4 t ha^?1 poultry manure, and 4 t ha^?1 of leaves of Senna spectabilis), and maize cultivars (ATP-SR-Y – an acid soil-tolerant, and Tuxpeño sequia – an acid susceptible). On acid soil, maize grain yield of ATP-SR-Y was 61% higher than the grain yield of Tuxpeño sequia. Continuous maize cultivation on acid soil further increased soil acidity, which was manifested by a decrease in pH (0.23 unit), exchangeable Ca (31%) and Mg (36%) and by an increase in exchangeable Al (20%). Yearly application of 60 kg ha^?1 of P for 3 years increased soil acidity through increases in exchangeable Al (8%) and H (16%) and a decrease in exchangeable Ca (30%), Mg (11%) and pH (0.07 unit). Lime application increased grain yield of the tolerant (82%) and susceptible (208%) cultivars. The grain yield increases were associated with a mean decrease of 43% in exchangeable Al, and 51% in H, a mean increase of 0.27 unit in pH, 5% in CEC, 154% in exchangeable Ca, and 481% in Mg contents of the soil. Poultry manure was more efficient than leaves of Senna producing 38% higher grain yield. This yield was associated with increases in pH, Ca, Mg and P, and a decrease in Al. The highest mean grain yields were obtained with lime added to poultry manure (4.70 t ha^?1) or leaves of Senna (4.72 t ha^?1). Grain yield increase was more related to the decrease in exchangeable Al (r = ?0.86 to ?0.95, P<0.01) and increase in Ca (r = 0.78–0.94, P<0.01), than to pH (r = ?0.57 (non-significant) to ?0.58 (P<0.05)). Exchangeable Al was the main factor determining pH (r = ?0.88 to ?0.92, P<0.01). The yield advantage of the acid tolerant cultivar was evident even after correcting for soil acidity. Acid soil-tolerant cultivars are capable of bringing unproductive acid soils into cultivation on the short run. The integration of soil amendments together with acid soil-tolerant cultivar offers a sustainable and comprehensive strategy for the management of acid soils in the tropics.     

Field Evaluation of Willow Under Short Rotation Coppice for Phytomanagement of Metal-Polluted Agricultural Soils

Short rotation coppice (SRC) of willow and poplar might be a promising phytoremediation option since it uses fast growing, high biomass producing tree species with often a sufficient metal uptake. This study evaluates growth, metal uptake and extraction potentials of eight willow clones (Belders, Belgisch Rood, Christina, Inger, Jorr, Loden, Tora and Zwarte Driebast) on a metal-contaminated agricultural soil, with total cadmium (Cd) and zinc (Zn) concentrations of 6.5 ± 0.8 and 377 ± 69 mg kg^?1 soil, respectively. Although, during the first cycle, on average generally low productivity levels (3.7 ton DM (dry matter) ha^?1 y^?1) were obtained on this sandy soil, certain clones exhibited quite acceptable productivity levels (e.g. Zwarte Driebast 12.5 ton DM ha^?1 y^?1). Even at low biomass productivity levels, SRC of willow showed promising removal potentials of 72 g Cd and 2.0 kg Zn ha^?1 y^?1, which is much higher than e.g. energy maize or rapeseed grown on the same soil. Cd and Zn removal can be increased by 40% if leaves are harvested as well. Nevertheless, nowadays the wood price remains the most critical factor in order to implement SRC as an acceptable, economically feasible alternative crop on metal-contaminated agricultural soils.     

The dynamics of soil redistribution and the implications for soil organic carbon accounting in agricultural south‐eastern Australia

Anthropogenically induced change in soil redistribution plays an important role in the soil organic carbon (SOC) budget. Uncertainty of its impact is large because of the dearth of recent soil redistribution estimates concomitant with changing land use and management practices. An Australian national survey used the artificial radionuclide caesium‐137 (¹³⁷Cs) to estimate net (1950s–1990) soil redistribution. South‐eastern Australia showed a median net soil loss of 9.7 t ha^?1 yr^?1. We resurveyed the region using the same ¹³⁷Cs technique and found a median net (1990–2010) soil gain of 3.9 t ha^?1 yr^?1 with an interquartile range from ?1.6 t ha^?1 yr^?1 to +10.7 t ha^?1 yr^?1. Despite this variation, soil erosion across the region has declined as a likely consequence of the widespread adoption of soil conservation measures over the last ca 30 years. The implication of omitted soil redistribution dynamics in SOC accounting is to increase uncertainty and diminish its accuracy.     

Bioavailability and extraction of heavy metals from contaminated soil by Atriplex halimus

Pot experiments were performed to evaluate the phytoremediation capacity of plants of Atriplex halimus grown in contaminated mine soils and to investigate the effects of organic amendments on the metal bioavailability and uptake of these metals by plants. Soil samples collected from abandoned mine sites north of Madrid (Spain) were mixed with 0, 30 and 60 Mg ha⁻¹ of two organic amendments, with different pH and nutrients content: pine-bark compost and horse- and sheep-manure compost. The increasing soil organic matter content and pH by the application of manure amendment reduced metal bioavailability in soil stabilising them. The proportion of Cu in the most bioavailable fractions (sum of the water-soluble, exchangeable, acid-soluble and Fe–Mn oxides fractions) decreased with the addition of 60 Mg ha⁻¹ of manure from 62% to 52% in one of the soils studied and from 50% to 30% in the other. This amendment also reduced Zn proportion in water-soluble and exchangeable fractions from 17% to 13% in one of the soils. Manure decreased metal concentrations in shoots of A. halimus, from 97 to 35 mg kg⁻¹ of Cu, from 211 to 98 mg kg⁻¹ of Zn and from 1.4 to 0.6 mg kg⁻¹ of Cd. In these treatments there was a higher plant growth due to the lower metal toxicity and the improvement of nutrients content in soil. This higher growth resulted in a higher total metal accumulation in plant biomass and therefore in a greater amount of metals removed from soil, so manure could be useful for phytoextraction purposes. This amendment increased metal accumulation in shoots from 37 to 138 mg pot⁻¹ of Cu, from 299 to 445 mg pot⁻¹ of Zn and from 1.8 to 3.7 mg pot⁻¹ of Cd. Pine bark amendment did not significantly alter metal availability and its uptake by plants. Plants of A. halimus managed to reduce total Zn concentration in one of the soils from 146 to 130 mg kg⁻¹, but its phytoextraction capacity was insufficient to remediate contaminated soils in the short-to-medium term. However, A. halimus could be, in combination with manure amendment, appropriate for the phytostabilization of metals in mine soils.