Phytoextraction of Zinc by Indian Mustard and Tall Fescue

Abstract

This experiment evaluated the capacity of two species, Indian mustard (Brassica juncea Czern.) and tall fescue (Festuca arundinacea Schreb.) to extract zinc (Zn) from soils. Also, this experiment focused on using nitrogen (N) fertilizers to increase the phytoextraction of Zn. Two soils of the Hadley series (Typic Udifluvents) were studied. A treatment array of Zn concentrations in soils was supplied as zinc sulfate. Nitrogen was supplied at 200 mg N/kg of soil as calcium nitrate, urea, or compost. Two successive plantings of Indian mustard in the same media were grown until flowering and harvested. Fescue was grown from seeding to a height of 15 cm, harvested, grown again in the same media to a height of 15 cm, and harvested again. After the second harvests of Indian mustard and fescue, soil samples were taken for analysis of extracts with water and with Morgan's solution. Indian mustard was grown with Zn additions ranging from 0 to 100 mg/kg soil. The shoot mass of Indian mustard in both harvests increased to a soil‐Zn level of 25 mg/kg and then decreased. Although growth decreased as the soil‐Zn levels increased beyond 25 mg/kg, Zn concentration and total accumulation increased linearly as the soil‐Zn levels increased. Zinc concentration and accumulation in Indian mustard were highest in soils amended with urea and were lowest in soils with no fertilizer. Fescue was grown with Zn additions ranging from 0 to 1000 mg/kg soil. The shoot mass of fescue increased to a soil‐Zn level of 125 mg/kg (harvest 1) or 250 mg/kg (harvest 2) and then decreased as the soil‐Zn levels increased. Concentration and accumulation of Zn in fescue increased linearly as the soil‐Zn levels increased. Zinc concentration and accumulation were highest in fescue grown in soils amended with urea and lowest in soils with no fertilizer. The highest accumulation of Zn in fescue (3800 mg/pot) occurred at 1000 mg Zn/kg soil. Highest concentrations of soil Zn were extracted with Morgan's solution or water from soils amended with urea, regardless of the species grown in the soils. Lowest concentrations of Zn were extracted from soils with no fertilizer added, regardless of extract or species. In general, if fertilizers (calcium nitrate, urea, or compost) were added to the soils, the pH decreased. Fescue was easy to grow, tolerated much higher soil‐Zn levels than Indian mustard in this research, and could be a species useful for phytoextraction of Zn.     

Bioavailability of zinc and lead from a contaminated soil amended with pine bark-goat manure compost

The distribution in soil and plant uptake of zinc (Zn) and lead (Pb) as influenced by pine bark-goat manure (PBG) compost additions were investigated from the soils artificially contaminated with Zn or Pb ions using maize (Zea mays L.) as a test crop. Soils were amended with four rates of pine bark-goat manure compost (0, 50, 100, and 200 tons ha^?1) and four rates (0, 300, 600 and 1200 mg kg^?1) of Zn or Pb. Maize was planted and grown for 42 days. At harvest, plants samples were analyzed for Zn and Pb concentration. Soils samples were analyzed for pH, extractable and diethylene triamine pentaacetic acid (DTPA) extractable Zn and Pb. Extractable Zn and Pb was lower in PBG compost amended soils than in unamended soils and steadily declined with increasing amount of compost applied. The extractable fraction for Zn dropped by 62.2, 65.0 and 44.6% for 300, 600 and 1200 mg Zn kg^?1, respectively when 200 t ha^?1 of PBG compost was applied. Metal uptake by maize plants were directly related to the rate of applied heavy metal ions with greater concentrations of metals ions found where metal ions were added to non-amended soils.     

The Effects of Cow Manure and Vermicompost on Availability and Desorption Characteristics of Zinc in a Loamy Calcareous Soil

The application of organic fertilizers in soils not only increases soil organic matter but also introduces essential nutrients to soil. Therefore, applying these fertilizers can affect the availability and desorption characteristics of nutrients. The main objective of this research is to study the effects of cow manure (CM) and vermicompost (VC) on availability and desorption characteristics of zinc (Zn) in a loamy calcareous soil. In this study, concentration of available Zn (using DTPA-TEA, AB-DTPA, and Mehlich 3) and desorption characteristics of Zn (using successive extraction with DTPA-TEA For 1–504 h at 25 ± 1°C) in amended soil with 0, 0.5, and 1% (w/w) of CM and VC were investigated in a completely randomized design. Results of this research showed that concentration of Zn extracted by using three methods was higher in amended soils with 1% CM and VC than those with 0.5% of these fertilizers. Furthermore, the difference between concentration of available Zn in amended soils with CM and VC was not found to be significant (p > 0.05). The results of kinetics study illustrated that the effect of organic fertilizers on Zn desorbed after 504 h was found to be significant (p < 0.01). Amount of cumulative of Zn desorbed in amended soils was significantly (p < 0.05) higher than unamended soil. Concentration of Zn desorbed after 504 h in 0.5 and 1% of CM and VC compared with unamended soil increased 26, 54, 12, and 46%, respectively. In addition, Zn desorption rate in amended soils with CM was higher than those with VC. It can be concluded that organic fertilizers applied to loamy calcareous soils enhance source of available Zn for the plant. Moreover, the results of this study showed that the ability of amended soils with VC to supplying Zn for plants was lower than those with CM.     

Biomass and Cu and Zn Uptake of Two Turfgrass Species Grown in Sludge Compost–soil Mixtures

Two kinds of common turfgrass, fescue and ryegrass, were grown in soils amended with 20?×?80% sludge compost (SC) in this research. The effects of SC on two kinds of soil and response of fescue and ryegrass to the SC amendment were studied. The results showed that urease activity, extractable content of Cu and Zn and Electrical conductivity of both soils increased while pH decreased with the increase of SC amendment. However, the change of these parameters also depended strongly on soil characteristics. Sludge compost at the ≤40 and ≤60% levels can improve growth of fescue and ryegrass, respectively. The biomass of fescue grown in substrate with 40% SC increased 27% in a red soil and 44% in a yellow loamy soil compared to the control. The biomass of ryegrass grown in substrate with 60% SC increased 120% in the red soil and 86% in the yellow loamy soil. Sludge compost amendment at these levels did not significantly affect soluble salt contents of soil or Cu and Zn in plant tissue. Therefore, rational use of sludge compost can take advantage of its beneficial effect as a nutrient source for plant production while avoiding the potential deleterious effects on soil and plant.     

Effect of Environmentally Friendly Amendment on a Newly Found Accumulator Kalimeris integrifolia Turcz. ex DC. Phytoremediating Cd-Contaminated Soil

Pot culture experiments were conducted to study the remediation potentials of a newly found accumulator Kalimeris integrifolia Turcz. ex DC. under different cadmium (Cd) concentrations with same fertilizer level, as well as the same Cd dose under different fertilizer doses. At medium (100 g/kg) chicken manure level, Cd concentrations in roots, stems, leaves, inflorescences, and shoots of K. integrifolia grown in the soils contaminated with 2.5, 5, 10, and 25 mg/kg Cd significantly decreased (p?<?0.05) in average by 23.8%, 29.9%, 24.0%, 30.1%, and 38.6%, respectively, when compared to those of the pots without addition of chicken manure. In contrast, the medium urea amendment level (1 g/kg) showed no effect on the bioaccumulated Cd concentrations of K. integrifolia regardless of the spiked Cd doses. However, Cd extraction capacities (micrograms per pot) of K. integrifolia shoots were significantly increased (p?<?0.05) due to the gain in biomass (more than one- to twofolds) by the soil fertilizing effect of urea and chicken manure. Particularly, Cd extraction capacities (micrograms per pot) of K. integrifolia shoots amended by urea were higher than that of chicken manure. Under the condition of 25 mg/kg Cd addition, shoot biomasses of K. integrifolia were significantly increased (p?<?0.05) with the amendment of chicken manure (50, 100, and 200 g/kg) and urea (0.5, 1, and 2 g/kg). As a result, the Cd extraction capacities (micrograms per pot) were increased in treatments even though soil extractable Cd concentrations were significantly decreased (p?<?0.05) by amendment with chicken manure and maintained by urea addition. For practical application concerns, chicken manure is better used as phytostabilization amendment owing to its reducing role to extractable heavy metal in soil, and urea is better for phytoextraction.     

Nitrogen availability to citrus seedlings from urea and from mineralization of citrus leaf or compost

A pot experiment was conducted using a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments) amended with either citrus leaves or compost, to measure the nitrogen (N) mineralization and its availability to two citrus rootstock seedlings. A rapid increase in NH₄‐N concentration was evident in the soil amended with citrus leaves as compared to compost during the initial 14 to 20 d. Subsequently, the concentration of NH₄‐N decreased in the citrus leaves amended soil. The extractable NO₃‐N concentration was greater in the soil amended with citrus leaves as compared to compost, throughout the 270 d duration of the study. The N concentrations and N uptake by Cleopatra mandarin (CM) and Swingle citrumelo (SC) seedlings grown in citrus leaf amended soil were very similar to those in urea amended soil. Therefore, mineralization of N from dry ground citrus leaves was quite rapid. The N concentrations in both rootstock seedlings were much lower in the compost amended and unamended soils as compared to those in either citrus leaves or urea amended soils. Rapid mineralization of N from cirrus leaves added to sandy soil, resulting in an increased availability of N, suggested that the contribution of N from shed leaf mineralization must be considered while developing N rate recommendations for improving N use efficiency.     

Effect of different organic amendments on the resistance and resilience of the organic matter decomposing ability of soil and the role of aggregated soil structure

Abstract

The effect of organic amendment on the resistance and resilience of the organic matter decomposing activity was compared between soils amended with compost and with chemical fertilizers. The impact of metam sodium disinfection on cellulose-decomposing activity and on the number of nematodes in three types of soils was periodically measured. In an andosol, cellulose-decomposing activity was significantly suppressed by soil disinfection only in the chemically fertilized soil (CF-soil) and not in the soils to which cow manure compost and okara (the residue in tofu production)/coffee compost was added. In a brown lowland soil, cellulose-decomposing activity was significantly suppressed by soil disinfection in the CF-soil, but not in the soils to which higher amounts of cow manure compost and pig manure compost had been added. In a red-yellow soil, cellulose-decomposing activity was significantly suppressed by soil disinfection in all soils, but its resilience was higher in the soils to which cow manure compost or coffee compost was added compared with the CF-soil. Total numbers of nematodes were markedly decreased by soil disinfection in all soils. These results may suggest that the resistance and resilience of cellulose-decomposing activity against soil disinfection were enhanced by organic amendments, while disinfection had fatal effects on soil nematodes. In most of the organically amended soils, the mean weight diameters of aggregates were larger compared with the CF-soils, suggesting that highly structured soil pore networks may provide shelters for the soil microbes responsible for cellulose decomposition against disinfection. This hypothesis was supported by the result that the resistance of cellulose-decomposing activity against soil disinfection decreased when the soil structure was destroyed by grinding in a mortal and pestle.     

Effect of different organic amendments on the resistance and resilience of the organic matter decomposing ability of soil and the role of aggregated soil structure

The effect of organic amendment on the resistance and resilience of the organic matter decomposing activity was compared between soils amended with compost and with chemical fertilizers. The impact of metam sodium disinfection on cellulose-decomposing activity and on the number of nematodes in three types of soils was periodically measured. In an andosol, cellulose-decomposing activity was significantly suppressed by soil disinfection only in the chemically fertilized soil (CF-soil) and not in the soils to which cow manure compost and okara (the residue in tofu production)/coffee compost was added. In a brown lowland soil, cellulose-decomposing activity was significantly suppressed by soil disinfection in the CF-soil, but not in the soils to which higher amounts of cow manure compost and pig manure compost had been added. In a red-yellow soil, cellulose-decomposing activity was significantly suppressed by soil disinfection in all soils, but its resilience was higher in the soils to which cow manure compost or coffee compost was added compared with the CF-soil. Total numbers of nematodes were markedly decreased by soil disinfection in all soils. These results may suggest that the resistance and resilience of cellulose-decomposing activity against soil disinfection were enhanced by organic amendments, while disinfection had fatal effects on soil nematodes. In most of the organically amended soils, the mean weight diameters of aggregates were larger compared with the CF-soils, suggesting that highly structured soil pore networks may provide shelters for the soil microbes responsible for cellulose decomposition against disinfection. This hypothesis was supported by the result that the resistance of cellulose-decomposing activity against soil disinfection decreased when the soil structure was destroyed by grinding in a mortal and pestle.     

Effect of swine manure and urea on soil phosphorus supply to canola

Limited information exists as to the effect of liquid swine manure on soil phosphorus (P) availability in Western Canadian soil. Swine manure is most often applied to meet additional requirements for nitrogen (N) and research to date has emphasized N effects. The effect of swine manure and urea on P supply to canola was investigated under controlled environment condition. Canola (Brassica napus) was grown in pots with manure or urea added to two Saskatchewan soils (sandy loam and clay loam) at 0 and 100 mg N kg^‐1. Plants were grown to maturity, and yield and nutrient content were determined. Phosphorus supply rates in soils were measured in the pots using anion exchange resin membrane probes. Additions of swine manure and urea enhanced canola P accumulation and led to a higher proportion of P in seeds. This response was more evident in the manure treatment than with urea. Soil amended with manure significantly increased N and P supply rates in soils as the manure contains N and P. On the contrary, application of urea significantly increased N supply rate, but led to a slight decrease in the measured soil supply rate of available P. Despite the apparent decrease in soil supply of available P in urea treatment, canola maintained its N:P ratio by increasing P absorption, possibly due to a greater root mass.     

Redistribution and Availability of Iron,Manganese, Zinc,and Copper in Four Malian Agricultural Soils Amended with Solid Municipal Waste Compost

Abstract

Municipal waste compost can improve the fertility status of tropical soils. The redistribution of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in tropical soils after amendment with solid municipal waste compost was investigated. Four tropical agricultural soils from Mali characterized by poor trace‐element status were amended with compost and incubated for 32 weeks at 35°C. The soil were analyzed at the beginning and the end of the incubation experiment for readily available fractions, organic fractions, and residual fractions as operationally defined by sequential extraction. Readily available Fe increased significantly with compost application in most soils. Readily available Mn was mostly unaffected by compost application. After 32 weeks, readily available Zn had increased, and readily available Cu had decreased. Readily available levels of the elements remained greater than deficiency levels in the compost‐amended soils. Organic fractions of the elements increased after compost addition. The organic fractions and residual forms, depending on the element and the soil, remained constant or increased within the duration of the experiment.     

Availability of organic nutrient sources and their effects on yield and nutrient recovery of tef [Eragrostis tef (Zucc.) Trotter] and on soil properties

Inadequate nutrient and organic‐matter supply constitutes the principal cause for declining soil fertility and productivity in much of sub‐Saharan Africa (SSA). In a survey in Gare Arera, the central Ethiopian highland, farmyard manure (FYM) and compost enriched with ash were identified as underutilized organic nutrient sources. Mustard meal, a by‐product of mustard‐seed oil production, is also locally available. On‐farm experiments were carried out on two major soil types (Nitisol and Vertisol) to study effects of the organic fertilizers, synthetic fertilizer (urea + triple superphosphate) and an unfertilized control on the yield and yield components of tef [Eragrostis tef (Zucc) Trotter] and selected soil properties. Application of organic fertilizers at an N rate equivalent to that of urea produced grain yields of 82% and 99% of that produced with urea on Nitisol and Vertisol, respectively. The apparent N recovery from urea, mustard meal, FYM, and compost was, respectively, 31%, 25%, 16%, and 28% on Nitisol and 23%, 17%, 26%, and 21% on Vertisol. The mean agronomic efficiency for the organic and synthetic fertilizers on Nitisol was 20 and 24 kg grain (kg N)^–1 applied, respectively, whereas on the Vertisol, it was 13 kg grain (kg N)^–1 for both. On Vertisol, tef was most responsive to FYM and on Nitisol, it was most responsive to compost. Soil N and P contents increased due to organic‐fertilizer application. The results showed that compost enriched with ash is a good choice on Nitisol while FYM works well on Vertisol. Mustard meal can be applied on both soils.     

Micronutrient Concentration in Horticultural Crops Grown on a Soil Amended with the Solid Phase of Pig Slurry

Abstract

Previous studies carried out on metal fractionation have shown that more than 95% of metals are in the solid phase of pig slurries (SPPS), with copper (Cu), and zinc (Zn) being the commonly occurring micronutrients in animal slurries. The input of micronutrients associated with the application of SPPS could be an important pathway for the supply of these essential elements to arable crops in bioavailable forms, especially in calcareous soils, which induce the immobilization of these elements. The aim of this work was to study the effect of application of pig manures (fresh and composted) derived from the SPPS on the micronutrient—iron (Fe), Cu, Magnesium (Mn), and Zn—concentration on amended calcareous soils in horticultural plants (cucumber and Milan cabbage). In addition, the effect of composting and application rates were analyzed. The experiment was conducted in field conditions on a Xerofluvent soil with a clayey‐loam texture. The organic wastes used in this study were uncomposted and composted solid fractions of swine manure slurry (UC‐SPPS and C‐SPPS, respectively) at two different rates (supplying 300 kg N ha^?1 and 450 kg N ha^?1 respectively). A mineral fertilizer treatment equivalent to 300 kg N ha^?1 and a control treatment without fertilization were also included for comparison. The use of SPPS amendment induced a biomass production similar to the mineral fertilizer for cucumber, but higher in Milan cabbage plants, without any yield increment associated with the increased application rate of SPPS or composting. Micronutrient concentration in cucumber and cabbage plants was affected by the SPPS amendment, with an increase of Mn and Zn uptake and a decrease of Cu, compared to the control. The increasing application rate of SPPS did not induce a general increase in the plant uptake of micronutrients; the opposite was true for the crops grown in the C‐SPPS‐amended soils.     

Carbon‐mineralization kinetics in an organically managed Cambic Arenosol amended with organic fertilizers

The dynamics of C mineralization in an organically managed Cambic Arenosol amended with hen manure, a stabilized compost (compost), and three different combinations of both fertilizers (varying from a 1:100 to a 1:10 ratio) were studied during an incubation experiment to estimate the potential of such combinations to preserve/restore soil C content relative to single applications. A strong increase of the CO₂‐C emissions relative to the unamended soil (control) was observed after soil application of all five organic‐fertilizer treatments. A significantly higher amount of applied C was lost in hen‐manure treatment (648 mg CO₂‐C [g C applied]^–1) when compared to compost (159 mg CO₂‐C [g C applied]^–1) or to the three combined treatments (176–195 mg CO₂‐C [g C applied]^–1). The first‐order exponential model and the double exponential model were used to fit the C‐mineralization data in the treatments considered. Results showed that mixing “small” amounts of hen manure with compost did not affect the total amount of potentially mineralizable C, but significantly increased the mineralization rate constant. Clearly, combinations of both fertilizers promoted an initial faster mineralization of the organic matter, and consequently a faster release of nutrients, without affecting the total amount of C sequestered in soil.     

Response of kentucky‐31 tall fescue to broiler litter and composts made from broiler litter

Abstract

Recycled paper treated with boric acid (BA) is gaining acceptance as bedding in broiler houses. Applying this litter to Kentucky 31 (K‐31) tall fescue, Festuca Arundinacea Shreb, pastures raises the issue of potential boron (B) toxicity. There is also the question of nitrogen (N) availability from composts made with borated paper and broiler manure. The effect of five N sources at 224, 448, and 896 kg N/ha in a factorial arrangement plus an unfertilized control and high nitrogen‐phosphorus‐potassium (NPK) + additional boron at 45 kg B/ha on growth and NPKB uptake of K‐31 tall fescue was determined in a greenhouse during the spring of 1992. The five N sources were (1) inorganic salts, (2) compost made from hen manure, broiler manure, fescue hay and bark (M1), (3) fresh broiler litter (M2), (4) compost made from broiler manure and borated paper bedding (M3), (5) compost from hen manure, oak leaves, broiler litter (M4). The soil was Cecil sandy clay loam subsoil. Six harvests were made at 4‐cm cutting heights for determination of dry matter, N, P, K, and B uptake in tops, stubble, roots, and residue. Relative yield response of M2 was 65% of that from inorganic NPK, whereas the yield of the three composts was 22–30% of that from inorganic NPK. Over 50% of the N applied in compost residue remained at the soil surface. Boron toxicity to K‐31 as estimated from yield reduction or from visual symptoms did not occur from 20 kg B/ha in compost made with borated paper (M3). However, a 12% yield reduction did occur at the 45 kg B/ha rate from inorganic B. Industry efforts to reduce the amount of boric acid used in the treatment of recycled paper, the high mobility of B in humid areas, the apparent ability of K‐31 tall fescue to tolerate massive quantities of compost and high rates of B application suggest that the application of the broiler litter from houses where BA‐treated recycled paper is used as bedding would be environmentally safe at application rates based on N requirements of K‐31 tall fescue.     

The Effect of Different Fertilizers’ Sources on Micronutrients’ Content and Sugar Quality of Sugar Beet

Abstract

In order to evaluate the effect of different fertilizers’ sources on micronutrients’ content and sugar quality of sugar beet, three fertilizers’ sources include spent mushroom compost (SMC) (29 t/ha), sheep manure (23 t/ha), chemical fertilizer including zinc sulfate (10?kg/ha), copper sulfate (10?kg/ha), iron sulfate (30?kg/ha), manganese sulfate (15?kg/ha) and no fertilizer (control) were conducted in a randomized complete block design with three replications at Research Farm of Shahrekord University in 2013. The results showed that micronutrients’ content in the root, α-amino-N sucrose percentage and sucrose yield were significantly affected by fertilizer treatments. The highest elements’ content of Fe (90.39?mg/kg), Zn (39.15?mg/kg), and Cu (18.1?mg/kg) in sugar beet root belonged to SMC treatment. Besides, SMC caused less α-amino-N accumulation in sugar beet compared with sheep manure (1.05 MEq/g). Sucrose percentage was higher in SMC treatment than the sheep manure. Likewise, sucrose percentage revealed a significant positive correlation with micronutrients of zinc, copper, and manganese in sugar beet root. Therefore, it could be concluded that using SMC increases micronutrients’ content in the root and at the same time, plays an important role in sugar quality improvement of sugar beet.     

Improvement of phytoremediation effects with help of different fertilizer

Abstract

Phytoremediation is increasingly used to remediate metal contaminated soils. However, in order to provide technically efficient phytoremediation of contaminated sites the plant yield and metal uptake have to be enhanced dramatically. The aim of the study was to find appropriate combination of plant species and fertilizers capable of improving yields of the plants and stimulate a transfer of metals to more available to the plants forms. Wheat Triticum vulgare was used for the phytoremediation research. To increase yield of crops and enhance mobility of metals in the rhizosphere the soils were amended with three fertilizers (urea, horse manure, and “ispolin”). Short-term (36 d) vegetation test showed that concentrations of heavy metals in the plants grown in contaminated soil (from site 2) were significantly higher than those in the plants grown in clean soil (from site 1). Growth of wheat resulted in a decrease of Cd content in the soil. Amendment of the contaminated soil with urea enhanced the effect and the decrease of Cd concentration in the soil was more significant. The best effect was demonstrated after application of ispolin: concentrations of Cd, Cu, Pb, and Zn in the rhizosphere decreased 1.2–1.4 times as compared with those in the initial contaminated soil (the decrease was statistically significant).     

Positive Effects of Biochar and Biochar-Compost on Maize Growth and Nutrient Availability in Two Agricultural Soils

Previous studies have reported positive, negative, or neutral effects on maize yield by the application of biochar and/or compost in the presence or absence of inorganic fertilization. This study investigated the influence of biochar, compost, and mixtures of the two, along with N fertilization, on maize (Zea mays L.) growth and nutrient status in two agricultural Mediterranean soils. Biochars (BC) were produced from grape pomace (GP) and rice husks (RH) by pyrolysis at 300°C (BC-GP; BC-RH). Maize was grown for 30 days after seedling emergence in a greenhouse pot trial in two Mediterranean soils (Sandy Loam-SL and Loam-L) amended with biochar or/and compost (BC-GP+compost; BC-RH+compost) at 2% (w/w) application rate with nitrogen (N) fertilization. The addition of BC-GP amendment resulted in the highest increase of aboveground dry weight (16 g/pot) compared to the control (6.27 g/pot) in SL soil, whereas in L soil the highest increase of aboveground dry weight resulted from BC-RH+compost (13.03 g/pot) compared to the control (2.43 g/pot). The addition of BC-GP+compost significantly increased phosphorus (P) concentration of the aboveground and belowground tissues only in L soil. Potassium (K) concentration of aboveground and belowground tissues significantly increased almost by all the amendments with the greatest increase being observed after the addition of BC-GP+compost in SL soil. To conclude, biochar addition could enhance plant growth, although soil conditions, type of biochar and additional fertilization should receive special attention in order to be used as a tool for sustainable agriculture.     

肥料重金属含量状况及施肥对土壤和作物重金属富集的影响

本文对肥料中重金属的含量状况以及施肥对土壤和农作物重金属累积影响的研究进展进行了系统分析和总结。过磷酸钙中锌（Zn）、 铜（Cu）、 镉（Cd）、 铅（Pb）含量高于氮肥、 钾肥和三元复合肥,有机-无机复混肥料中的Pb含量高于其他化肥。有机肥如畜禽粪便、 污泥及其堆肥中的重金属含量高于化肥,猪粪中的Cu、 Zn、 砷（As）、 Cd含量明显高于其他有机废弃物,鸡粪中铬（Cr）含量高;污泥和垃圾堆肥中Pb或汞（Hg）含量高。商品有机肥Zn、 Pb和镍（Ni）含量高于堆肥,Hg含量高于畜禽粪便。多数研究表明,氮磷钾配施与不施肥相比土壤Cd和Pb含量增加,施用有机肥比不施肥提高土壤Cu、 Zn、 Pb、 Cd含量。施用化肥对农作物重金属富集的影响不明确,而施用有机肥可提高作物可食部位Cu、 Zn、 Cd、 Pb 的含量,影响大小与有机肥种类、 用量、 土壤类型和pH以及作物种类等有很大关系。在今后的研究中应着重以下几个方面, 1）典型种植体系下土壤重金属的投入/产出平衡; 2）不同种植体系下长期不同施肥措施对土壤重金属含量、 有效性影响的动态趋势; 3）典型种植体系和施肥措施下土壤对重金属的最高承载年限; 4）现有施肥措施下肥料中重金属的最高限量标准。     

Phosphorus and trace metal dynamics in soils amended with poultry litter and granulates

Environmental sustainability of animal agriculture is strongly dependent upon development of approaches to minimize the potential environmental impacts of applying animal manures. The excess manure and its nutrients (primarily phosphorus) in intensive animal production regions may need to be exported to other areas to comply with increased regulations on manure management. In our previous study we generated a variety of granulated products from poultry litter to achieve export of excess litter from the southwestern Ozarks, AR, USA. Our objective in the present study was to determine the effect of the application of poultry litter and granulated litter products on phosphorus (P), arsenic (As), copper (Cu) and zinc (Zn) dynamics in two Arkansas soils (Dewitt silt loam and Hector sandy loam). Poultry litter and granulated products were mixed with the surface horizon (0–15 cm) of soils at two application rates: P‐based (100 kg total P per hectare) and N‐based (160 kg plant‐available N per hectare). Soil–litter mixtures were incubated at 25 °C for 21 days. Sub‐samples were removed at 1, 7 and 21 days to determine the solubility and availability of P, As, Cu and Zn in soils. Results suggest that when litter was applied at 100 kg total P per hectare, contents of P, As, Cu and Zn were significantly greater in the soils amended with litter and granulated products than in the control (soil alone). However, the contents of P, As, Cu and Zn did not significantly differ in the soils amended with either normal litter or granulated litter products at total P or plant‐available N‐based application rates. This suggests that poultry litter granulation is a sound management practice that can be used to reduce concerns with fresh litter transport and potentially improve P and trace element balances in intensive poultry production regions, especially when applied on a plant‐available N basis.     

Sulfur mineralization in two soils amended with organic manures,crop residues,and green manures

The mineralization of sulfur (S) was investigated in a Vertisol and an Inceptisol amended with organic manures, green manures, and crop residues. Field‐moist soils amended with 10 g kg^—1 of organic materials were mixed with glass beads, placed in pyrex leaching tubes, leached with 0.01 M CaCl₂ to remove the mineral S and incubated at 30 °C. The leachates were collected every fortnight for 16 weeks and analyzed for SO₄‐S. The amount of S mineralized in control and in manure‐amended soils was highest in the first week and decreased steadily thereafter. The total S mineralized in amended soils varied considerably depending on the type of organic materials incorporated and soil used. The cumulative amounts of S mineralized in amended soils ranged from 6.98 mg S (kg soil)^—1 in Inceptisol amended with wheat straw to 34.38 mg S (kg soil)^—1 in Vertisol amended with farmyard manure (FYM). Expressed as a percentage of the S added to soils, the S mineralized was higher in FYM treated soils (63.5 to 67.3 %) as compared to poultry manure amended soils (60.5 to 62.3 %). Similarly the percentage of S mineralization from subabul (Leucaena leucocephala) loppings was higher (53.6 to 55.5 %) than that from gliricidia (Gliricidia sepium) loppings (50.3 to 51.1 %). Regression analysis clearly indicated the dependence of S mineralization on the C : S ratio of the organic materials added to soil. The addition of organic amendments resulted in net immobilization of S when the C : S ratio was above 290:1 in Vertisol and 349:1 in Inceptisol. The mineralizable S pool (S_o) and first‐order rate constant (k) varied considerably among the different types of organic materials added and soil. The S_o values of FYM treated soils were higher than in subabul, gliricidia, and poultry manure treated soils.