Potato absorption and phytoavailability of Cd,Ni, Cu,Zn and Pb in sierozem soils amended with municipal sludge compost

Effects of sludge utilization on the mobility and phytoavailability of heavy metals in soil-plant systems have attracted broad attention in recent years. In this study, we analyzed the effects of municipal sludge compost(MSC) on the solubility and plant uptake of Cd, Ni, Cu, Zn and Pb in a soil-potato system to explore the mobility, potato plant uptake and enrichment of these five heavy metals in sierozem soils amended with MSC through a potato cultivation trial in Lanzhou University of China in 2014. Ridge regression analysis was conducted to investigate the phytoavailability of heavy metals in amended soils. Furthermore, CaCl_2, CH_3 COONH_4, CH_3COOH, diethylene triamine pentacetic acid(DTPA) and ethylene diamine tetraacetic acid(EDTA) were used to extract the labile fraction of heavy metals from the amended soils. The results show that the MSC could not only improve the fertility but also increase the dissolved organic carbon(DOC) content of sierozem soils. The total concentrations and labile fraction proportions of heavy metals increase with increasing MSC percentage in sierozem soils. In amended soils, Cd has the highest solubility and mobility while Ni has the lowest solubility and mobility among the five heavy metals. The MSC increases the concentrations of heavy metals in the root, stem, peel and tuber of the potato plant, with the concentrations being much higher in the stem and root than in the peel and tuber. Among the five heavy metals, the bioconcentration factor value of Cd is the highest, while that of Ni is the lowest. The complexing agent(DTPA and EDTA) extractable fractions of heavy metals are the highest in terms of phytoavailability. Soil properties(including organic matter, p H and DOC) have important impacts on the phytoavailability of heavy metals. Our results suggest that in soil-potato systems, although the MSC may improve soil fertility, it can also increase the risk of soils exposed to heavy metals.     

土壤养分有效性测定及其方法

在提出土壤养分有效性测定概念的基础上 ,本文对各种土壤养分有效性的测定方法进行了总结 ,讨论了这些方法的测定机理、测定效果及近几年的进展。这些方法包括用于磷钾等元素测定的树脂法、用于氮测定的生物培养法和化学提取法、磷测定的氧化铁试纸法和氢氧化铁透析管法和钾的四苯硼钠法     

生物炭对京郊沙化地土壤性质和苜蓿生长、养分吸收的影响

通过田间试验研究了施用生物炭(14 t·hm^-2)和种植苜蓿对京郊沙化地的改良作用。试验设裸地(BL)、裸地添加生物炭(BLB)、种植苜蓿不加生物炭(A)和种植苜蓿添加生物炭(AB)四个处理。结果表明:添加生物炭使土壤容重显着减小11.5%~11.6%,pH值显着增加0.1~0.2个单位,田间持水量和总孔隙度分别增加9.1%~10.3%和7.6%~11.3%,土壤总氮、有机碳含量和氮、磷、钾、锌的有效含量分别增加10.3%~25.8%、52.8%~71.7%、12.7%~23.5%、141.7%~233.3%、47.7%~81.1%、94.2%~95.2%,有效铁含量最高减小29.1%,阳离子代换量(CEC)和钙、镁、锰、硼的有效含量无显着变化;种植苜蓿没有显着影响土壤pH值、容重、总孔隙度、田间持水量、CEC和氮、钙、镁、锌、硼的有效性,总体上显着减小了土壤含水量和总氮、速效磷、速效钾的含量,增加了铁和锰的有效含量。BLB处理土壤含水量比BL显着增加13.9%(P<0.05);添加生物炭使苜蓿地上部生物量、含水量和氮、磷、钾、钙、镁、铁、锌、锰、硼的吸收累积量分别显着增加91.1%、3.6%、110.0%、130.9%、200.4%、82.6%、44.8%、89.5%、102.7%、99.5%、104.7%.生物炭与苜蓿种植相结合可在短期内改善京郊沙化地土壤的理化性质、提高养分有效性和恢复植被。     

设施菜地土壤中速效磷是镉生物有效性的关键调控因子

通过田间实地调查与取样分析,运用简单相关、回归方程拟合和主成分分析等方法,研究了关中设施蔬菜种植区土壤中镉(Cd)的生物有效性及其与土壤速效磷含量(AP)、有机质含量(OM)和pH值等土壤基本理化性质的相关性,并研究了各基本理化因子对其的调控作用。结果表明:(1)研究区内设施菜地土壤中镉的有效态含量(DTPA浸提,CdA)与设施菜地土壤中速效磷含量、有机质含量和pH值均存在显著相关关系(P0.05),与土壤阳离子交换量、电导率不相关。(2)通过对土壤有效镉含量和与其呈显著相关关系的土壤基本理化性质指标分别进行回归方程拟合得出:y1[CdA]=0.501 5x1[AP]+0.010 6(R2=0.345 2,P0.01)、y2[CdA]=0.370 7x2[OM]+0.028 6(R2=0.139 0,P0.01)、y3[CdA]=-0.055 2x3[pH]+0.564 1(R2=0.050 9,P0.05),土壤中有效镉含量主要受以上三个因子的影响;通过多元回归方程拟合,土壤有效态镉含量的表达式为y4[CdA]=0.174 8+0.435 2x1[AP]+0.049 0lgx2[OM]-0.013 2x3[pH](R2=0.368 6,P0.01);主成分分析发现,土壤速效磷含量是设施菜地土壤中镉的生物有效性的关键调控因子。(3)研究区蔬菜果实中镉含量与土壤镉有效态含量的相关系数为0.464,高于其与土壤镉全量(CdT)的相关系数(0.387),从食品安全和健康风险控制的角度考虑,在设施菜地土壤污染风险评价中,认为以土壤镉有效态含量替代土壤镉全量可以更准确地表征土壤镉的安全风险。因此,设施蔬菜生产过程中,应严格控制土壤速效磷含量,以降低土壤有效镉含量,从而保证设施蔬菜产品的食品安全。     

Evaluation of immobilizing agents as soil quality conditioners in addition to their metal(loid) immobilizing effect

In trace metal (TM)-contaminated agricultural soils,management of TM availability is important for safe crop production.In addition,maintenance or improvement of soil quality is vital for sustainable crop cultivation.Decreased TM phytoavailability and increased soil quality can be achieved by the application of various immobilizing agents to soil,which can supply both macronutrients and organic matter.This study investigated the long-term influences of four common immobilizing agents on soil biogeochemical properties and the phytoavailability of TMs in mixed metal-contaminated soil from a cultivated upland near an abandoned mining site.Lime (L),gypsum (G),fly ash (F),and animal manure-based compost (C) were applied to pots containing contaminated soil,either individually or in combination.After incubation for three years under sequential cultivation of two crops and fallow,soil biogeochemical properties were determined,and Brassica rapa plant bioassay was performed.The phytoavailability of all TMs (both cationic metals and anionic metalloids) remained significantly lower in soils treated with immobilizing agents even after three years,when compared with the no-agent control (CK) soil.In addition,the soil quality was significantly improved by treatment with immobilizing agents.For instance,the C and L+C treatments were the most effective in improving soil physical (bulk density,porosity,and water-resistant aggregate stability),chemical (pH,organic matter,total nitrogen,cation exchange capacity,and plant-available phosphorus,magnesium,and potassium),and biological (microbial biomass carbon and dehydrogenase activity) properties.The improvement of soil properties and lowering of TM bioavailability were also consistent with the most significant increase in B.rapa biomass production observed in the C treatment,followed by the L+C,G+F,L,G,F,and L+G treatments,as compared with that in CK.These results indicate that the function of the TM-immobilizing agent as a soil quality conditioner,in addition to its TM immobilizing effect,should be considered when selecting such agents for agricultural or ecological applications.     

Crop use and profile distribution of phosphorus in soils that developed on mafic rocks in southern Portugal

The phytoavailability of soil phosphorus (P) depends on the different forms in which it occurs and how these forms change after the application of P fertiliser to the soil. Forms of P in the A, B and C horizons of eleven pedons that developed on mafic rocks were characterised by a fractionation method before and after fertilisation with single superphosphate, and a micropot experiment was conducted to assess the short-term use of P fertiliser by rye (Secale cereale L.). The main sources of P to the crop were (i) phosphate adsorbed on mineral surfaces and pedogenic Fe, Al or Ca phosphates in the A horizon and (ii) Ca-phosphates in B and C horizons. In the C horizons, poor in Fe/Al phases and clay, the precipitated Ca-P showed low solubility, resulting in a reduction in shoot biomass. The apparent P recovery by rye was similar in the A (36%) and B (29%) but decreased in the C (15%) horizons. The partial factor productivity (g g^?1) decreased from the A (58) to B (11) and C (5) horizons. P phytoavailability decreased with increasing profile depth because the transformation of P fertiliser to poorly soluble Ca-P forms increased with depth.     

Chemical and organic immobilization treatments for reducing phytoavailability of heavy metals in copper‐mine tailings

This study was conducted to evaluate the efficiency of diammonium phosphate (DAP), agricultural limestone (lime), and green‐waste compost mixed with 30% treated sewage sludge (GCS) applied alone or in combination as chemical immobilization treatment using tomato as a test crop. Mine waste was collected from an abandoned copper‐mine tailing site at Mynydd Parys, Anglesey (UK). Lime was applied at the rate of CaCO₃ equivalent (CCE, pH = 7), DAP at the rate of 23 g P per kg substrate, and 10% by weight, GCS as sole application. Half rate of each amendment was also tested as a combined treatment and an untreated substrate (control). Plant‐available metals (Cd, Cu, Fe, Pb, and Zn) were measured in substrate with conventional diethylenetriaminepentaacetic acid (DTPA) and sequential Ca(NO₃)₂ extraction. Plant–dry biomass yield was significantly (p < 0.001) increased by the combined application of all the three amendments while sole application of DAP reduced yield by 4‐fold compared to unamended soil probably due to P toxicity. Addition of lime reduced the DTPA‐extractable Cu, Fe, and Zn by 75%, 81%, and 85%, respectively, while Pb availability was reduced by 88% in combined DAP + lime + GCS treatment compared to control. The extraction capacity of DTPA was higher than that of Ca(NO₃)₂ by 3‐fold for Cu and Fe, 8‐fold for Pb, and 2‐fold for Zn. The leaf‐tissue concentrations of Cu and Fe were reduced by 77% and 83% in the lime + GCS amendment, respectively, while both Pb and Zn were reduced by 89% and 33%, respectively, in substrate treated with the combined application of all three amendments. These results suggest that alkaline amendments (both lime and GCS) were effective in reducing the phytoavailability of Cu, Fe, and Zn while DAP mixed with either GCS or lime was effective in reducing Pb availability.     

Land Application of Aluminum Water Treatment Residual: Aluminum Phytoavailability and Forage Yield

Negative impacts of land‐applied aluminum (Al)–rich water treatment residuals (WTRs), which have been suggested to improve soil phosphorus (P) sorption, could include excessive immobilization of plant‐available P and Al phytotoxicity. We studied the impacts of an Al‐rich WTRs on agronomic returns and plant Al concentrations in glasshouse and field studies. The glasshouse study was a 4 × 2 × 3 factorial experiment with one control in a randomized complete block design and three replicates. Four sources of P were each applied at two agronomic rate [44 kg P ha^?1, P‐based rate; and 179 kg plant‐available nitrogen (PAN) ha^?1, N‐based rate] to topsoil (0–15 cm) of a sandy, siliceous, hyperthermic Arenic Alaquods. Three WTR rates (0, 10, and 25 g kg^?1 oven‐dry‐weight basis) were further applied, whereas the control received neither P source nor WTRs. Bahiagrass (Paspalum notatum Fluggae), ryegrass (Lolium perenne L.), and a second bahiagrass crop were continuously grown in succession for 18 months. Applied WTRs increased soil Al but not plant Al concentrations (22–80 mg Al kg^?1), which fell within the normal concentration range for pasture plants. In the glasshouse, when WTRs were incorporated with the soil, bahiagrass dry matter (DM) accumulation was reduced, but ryegrass DM was not affected even at 25 g kg^?1 WTR. A 2‐year field study, with same treatments but two rates of WTRs (0 and 10 g kg^?1 WTR) surface applied to established bahiagrass on the same soil type (Spodosols) showed neither reduced yields nor increased plant Al phytoavailability in the WTR treatments. The studies show no increase in plant Al is associated with Al‐WTRs applied to reduce excess soil‐soluble P and P losses but plant DM accumulation may be reduced.     

Evaluation of Soil Tests for Plant‐available Mercury in a Soil–Crop Rotation System

A reliable soil test is needed for estimating mercury (Hg) availability to crop plants. In this study, four extraction procedures including 0.1 M hydrochloric acid (HCl), 1 M ammonium acetate (NH₄OAc) (pH 7.0), 0.005 M diethylenetriaminepentaacetic acid (DTPA), and 0.1 M calcium chloride (CaCl₂) (pH5.0) were compared for their adequacy in predicting soil Hg availability to crop plants of a rice–cabbage–radish rotation system. The amounts of Hg extracted by each of the four procedures increased with increasing equilibrium time. The optimal time required for extraction of soil Hg was approximately 30 min, though it varied slightly among the four extractants. The amounts of Hg extracted decreased with increasing soil/solution ratio, and a soil/solution ratio of 1:5 appeared to be adequate for soil Hg availability tests. The amounts of Hg extracted increased in the order of NH₄OAc < CaCl₂ < DTPA < HCl in silty loam soil (SLS) soil, and the order was NH₄OAc < CaCl₂ ≈ DTPA < HCl in yellowish red soil (YRS) soil. Significant positive correlations among the four extractants were obtained in SLS soil. In contrast, the correlations were poor in YRS soil, especially for HCl. There were significant correlations between concentrations of Hg in edible tissue of three plants and the amounts of soil Hg extractable to the four extractants for soil–rice system and soil–radish system, but not for soil–Chinese cabbage system. The 0.1M HCl extraction overall provided the best estimation of soil‐available Hg and could be used to predict phytoavailability of Hg in soil–crop systems.     

Phytoavailability of Some Micronutrients (Zn and Cu), Heavy Metals (Pb,Cd), and Yield of Rice Affected by Sewage Sludge Perennial Application

A study was conducted as a split-plot arrangement based on a randomized complete block design with three replications to test sewage sludge (SS) influence on yield and phytoavailability of lead (Pb), cadmium (Cd), zinc (Zn), and copper (Cu) by rice. The results indicated that fertilizer (main factor) and application periods (subfactor) affected studied traits. Three years of application of 40 ton ha^?1 SS + 50% chemical fertilizer (CF) gave the greatest paddy yield. The greatest Cu uptake by grain (10.38 ppm) occurred with 3 years application of 20 ton ha^?1 SS. With application of 40 ton ha^?1 SS + 50% CF, the greatest contents of Cd in root and Pb in shoots were recorded. The greatest accumulations of Cd in shoot and Zn in grain (30.56 and 25.81 ppm, respectively) were determined with the 20 ton ha^?1 SS treatment, as well. The greatest concentrations of Pb and Cd in grain (102.2 and 14.78 ppm, respectively) and Pb in root (552.2 ppm) were obtained with 3 years of application of 40 ton ha^?1 SS + 50% CF.