Sewage sludges in Hawaii: Chemical composition and reactions with soils and plants

Sewage sludges from six wastewater treatment plants in Hawaii were periodically sampled to determine the seasonal variation of their elemental composition. The Sand Island and Honouliuli treatment plants produced primary sludges averaging 1.6% and 2.0% total N, respectively. The Kailua, Kaneohe, Waimanalo, and Waianae treatment plants produced secondary sludges averaging 5.4, 5.1, 6.1, and 3.5% N, respectively. All the sludges tested were virtually devoid of K with concentration ranging from 0.01 to 0.15%, which was less than half of the 0.30% K considered typical for a US sewage sludge. Mean concentrations of Cd, Cu, Fe, Ni, and Zn in the Hawaii sludges were 5.9, 373, 12343, 218, 36.7, and 817 mg kg^?1, respectively, which were within the norms for sludge heavy metals as reported by the US Environmental Protection Agency. Seasonal variations in elemental concentration were small and only statistically significant for Ca and Zn. Sludges from the three treatment plants with highest annual production (Sand Island, Honouliuli, and Kailua) were then mixed at 5, 50, and 250 g kg^?1 with three representative tropical soils (a Mollisol, and Oxisol, and an Ultisol) to study sludge-soil reactions and plant responses. Soil-solution data indicated that chemical properties of a sludge-soil mixture depended not only on the soil, sludge, and its application rate, but also on sludge-soil interactions. At an agricultural rate of 5 g kg^?1 (10 Mg ha^?1), the anaerobically digested Kailua sludge increased corn (Zea mays L.) biomass, whereas the two undigested sludges reduced it. At higher rates, Mn phytotoxicity resulted from sludge applications to the Mollisol and Oxisol, both of which contained reducible Mn nodules. Significant growth reductions would be expected when corn seedlings contained ≥200 mg Mn kg^?1 or ≤0.30 % Ca; and, adequate supplies of Ca and Zn seemed to lessen Mn phytotoxicity.     

Fractionation of residual cadmium,copper, nickel,lead, and zinc in previously sludge‐amended soil

Abstract

The fractionation of heavy metals in previously sludge‐amended soil is important to evaluate their behavior in the environment in terms of mobility and availability to crop plants. A surface soil that received two types of sludges at two different rates, plus fertilizer only and no treatment (control), having been fallow for nine years, was used in this study. The contents of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) fractions in previously sludge‐amended soils were governed by the total content of these metals in the sludges applied and by the rate of sludge application. The contents of these metals were higher for soils that received the Chicago sludge as compared to that receiving the Huntsville sludge. Furthermore, soils that received 20 Mg/ha/yr of sludge for five years generally had higher levels of these metals than those receiving a single dose at the 100 Mg/ha application rate. The percentage of the total content in the water soluble and exchangeable forms was very low (≤1%) regardless of sludge application. The application of sludges tended to reduce the residual fraction and to increase the organic and carbonate fractions. Overall, the predominant forms of the metals in the sludges were as the Cd‐, Ni‐, Pb‐, and Zn‐carbonate and Cu‐organic fractions.     

Ameliorating subsoil acidity by surface application of calcium fulvates derived from common organic materials

Subsoil acidity is a serious constraint to crop production, and is difficult to correct by conventional liming practices. Thus, a different approach to ameliorating acid subsoils was evaluated. Subsoil material of an acid Ultisol (pH 4.4) was packed into 50-cm long columns, then leached with solutions of CaCl₂, CaCO₃ (suspension) or Ca fulvates prepared from chicken manure, cowpea green manure, or sewage sludge. The total water applied was 30.26 cm (or 800 ml) in 2 days. Thereafter, the columns were dismantled and cut into 5-cm segments for chemical analysis. The results indicated that only 2% of the added Ca from CaCO₃ moved past the 15-cm depth, compared to 68% from CaCl₂ and 35–75% from Ca fulvates. Correspondingly, CaCO₃ precipitated all KCl-extractable Al in the top 5 cm, but had no effect beyond the 10-cm depth. The CaCl₂ displaced a small but significant portion of extractable Al from the top 15 cm and redeposited some of that Al in lower depths. Similar to CaCO₃, Ca fulvates from chicken manure and green mamure only decreased extractable Al significantly in the top 10-cm layers, but had little effect beyond that depth. By contrast, the Ca fulvate from sewage sludge decreased Al down to the 45-cm depth. In terms of reducing Al saturation as a percentage of total extractable cations (effective cation exchange capacity), the Ca fulvates were as effective as CaCO₃ in the 0-to 5-cm layer, and more effective than CaCl₂ in any soil layer because of the increased exchangeable Ca and/or decreased Al. In general, surface application of common organic material-derived Ca fulvates can increase subsoil Ca and decrease the Al saturation percentage. However, Mg depletion and enrichment of unwanted metals (e.g., Na or heavy metals) may be a problem when leaching with these organic sources.     

Combination of Different Extractants to Assess Binding Forms of Some Elements in Soil Profiles

Abstract

Three different chemical extractants were evaluated as to their extraction efficiency for copper (Cu), zinc (Zn), lead (Pb), aluminium (Al), iron (Fe), chromium (Cr), manganese (Mn), potassium (K), magnesium (Mg), and calcium (Ca) on forest soil profiles from the Romanian Carpathians. The extractants were hot 14 M nitric acid (HNO₃), 0.05 M hydrochloric acid (HCl), and 0.1 M sodium pyrophosphate. By comparing amounts extracted by 0.05 M HCl and 0.1 M sodium pyrophosphate relative to that dissolved by hot 14 M HNO₃, some conclusions were drawn concerning the chemical forms of the metals in the extractable pool. The amount released by 0.05 M HCl was generally less than 10% of the HNO₃‐extractable fraction but showed considerable variation among the elements studied. The relative amount extracted by pyrophosphate increased with organic‐matter content of the soils for Cu, Zn, Pb, Al, Fe, and Cr; stayed more or less constant for Mn, K, and Mg; and decreased for Ca. These findings are discussed with respect to the different binding forms of the metals in the soil and the processes affecting their mobility. From the present results, the metals were ranked as follows with respect to their ability to form organic complexes in natural soils: Cu>Cr, Pb>Ca>Al>Fe, Zn, Mn, K>Mg. However, the use of cold dilute HCl as a fractionation step may be questionable in cases of soils with a high content of substances possessing large neutralization capacity for protons.     

MANURING EFFECT ON RICE GRAIN YIELD AND EXTRACTABLE TRACE ELEMENTS IN SOILS

Animal manures contain significant amounts of plant-available nutrients which could increase crop yields. They also contain heavy metals which may be exported outside soil systems by plants, animal and surface and underground water following application to soils. The effect of some animal manures on rice yield and extractability of iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) were determined in fours soils with different properties. The manures were applied at the rate of 100Mg ha^?1, and rice was grown for two consecutive seasons. In the second of the two seasons, rice yield and yield components were determined. Immediately after the second season rice harvest, soils were sampled and analyzed for DTPA extractable Fe, Zn, Mn, and Cu. Averaged across the soils, the level of extractable Fe increased by between 5% in chicken manure (PM) and 71% in cattle manure (CM); Zn by between 312% in CM and 871% in swine manure (SM); Mn by between 61% in PM and 172% in SM and Cu by between 327% in PM and 978% in SM. Mixing these manures before application reduced the level of extractable trace elements. Although there was increased yield following application, the results of this study indicated a possible risk of trace element export to the environment within a year, if high levels of the manures are applied.     

Assessment of Heavy Metals in Spinach (Spinacia oleracea L.) Grown in Sewage Sludge–Amended Soil

The assessment of heavy metals in spinach (Spinacia oleracea) grown in sewage sludge–amended soil was investigated. The results revealed that sewage sludge significantly (P < 0.01) increased the nutrients and heavy metals such as cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), and zinc (Zn) in the soil. The contents of metals were found to be below the maximum levels permitted for soils in India. The most agronomic performance and biochemical components of S. oleracea were found at 50% concentrations of sewage sludge in both seasons. The contents of Cd, Cr, Cu, Mn, and Zn in S. oleracea were increased from 5% to 100% concentrations of sewage sludge in both seasons. The order of contamination factor (Cf) of different heavy metals was Mn > Cd > Cr > Zn > Cu for soil and Cr > Cd > Mn > Zn > Cu for S. oleracea plants after application of sewage sludge. Therefore, use of sewage sludge increased concentrations of heavy metals in soil and S. oleracea.     

Bulk sediment bioassays with five species of fresh-water oligochaetes

The fluxes of metals (Na, K, Ca, Mg, Fe, Mn, Al, Cu, Zn, Pb, Cd, Cr, and Ni) in two spruce forest soils in S. Sweden were quantified using the lysimeter technique. Amounts in precipitation (dry and wet), throughfall, litterfall and annual accumulation in biomass were also quantified, as well as stores in soil and biomass. The metal concentrations of the soil solutions varied greatly according to season. The leaching of some metals (Fe, Cu, Pb, Cr, and organic forms of Al) was associated with the leaching of organic matter. These complexes were leached from the A horizon in considerable amounts. They were precipitated in the upper B horizon and only small amounts were transported further downward. By contrast, the leaching of Na, Mg, Ca, Mn, Cd, Zn, Ni, and inorganic forms of Al increased with increasing soil depth. The concentrations of these metals also increased with increasing soil solution acidity. The highest concentrations were often found at the transition to the C horizon. The amounts of Na, K, Mg, Ca, Mn, Al, Zn, Cd, Cr, and Ni leached from the rooting zone were found to be larger than the amounts deposited from the atmosphere, the main source of these metals being the mineral soil. The reverse was true of Ph, Cu, and Fe, the sink being the upper part of the B horizon.     

Effect of phosphorus‐enriched biochar and poultry manure on growth and mineral composition of lettuce (Lactuca sativa L. cv.) grown in alkaline soil

The use of pyrolysis products of manures gives positive effects on soil fertility, crop productivity and soil carbon sequestration. However, effects depend on soil characteristics, plant species and the raw material from which the biochar is derived, and some negative effects of biochar have been reported. The objective of this study was to evaluate the effectiveness of poultry manure (PM)‐derived biochar on the growth, and P, N, K, Ca, Mg, Fe, Zn, Cu and Mn concentration of lettuce (Lactuca sativa L.) plant. The treatments as follows: control, 20 g/kg poultry manure (PM), 20 g/kg phosphorus‐enriched poultry manure (PM+P), 10 g/kg Biochar (B), 10 g/kg Biochar+P (B+P). Application of biochar and PM significantly increased lettuce growth, and P‐enriched forms of PM and biochar gave the higher growth. PM has no significant effect on the N concentrations but biochar and, P‐enriched PM and biochar treatments significantly increased N concentrations. Phosphorus concentration of the lettuce leaves significantly increased by PM and biochar treatments. Plant K concentrations were also increased by PM and biochar, and their P‐enriched forms. Leaf Ca and Mg concentrations were lower in Biochar and B+P treatments than that of PM and PM+P treatments. Compared to control and PM treatments, biochar applications reduced Fe, Zn, Mn and Cu concentrations of the lettuce plants. The results of this study indicated that application of biochar to alkaline soil is beneficial for crop growth and N, P and K nutrition, but it certainly reduced Fe, Cu, Zn and Mn nutrition of lettuce.     

Evaluation of the Mehlich 3 soil extractant for upland Malawi soils

Abstract

The Mehlich 3 (M3) universal soil extraction method was compared with the ammonium acetate (AA), Bray 1, and DPTA extraction procedures for the analysis of calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P), zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe). Upland Malawi soils from 112 smallholder farmers’ fields of the Alfisol, Ultisol, and Oxisol soil orders were analyzed by the four procedures. Calcium, Mg, and K extracted by the M3 and AA procedures were highly correlated (r² = 0.98, 0.98, and 0.99 for the respective elements). The M3 extractant also correlated well with the DPTA procedure for Zn and Cu (r² = 0.88 for both elements) and the Bray 1 method for P (r² = 0.80). Amounts of Mn and Fe extracted by M3 and DPTA were poorly correlated (r² = 0.28 and 0.47, respectively), with both elements testing high in all soils. The high levels suggest that Mn and Fe deficiencies are likely to be rare, and that analysis for these elements is not generally necessary. Special precautions for Zn and Cu analyses are advised due to the low conentrations of these elements in the M3 extract and various laboratory sources of Zn contamination. The use of soil pH along with M3‐extractable Zn is recommended in the identification of potentially Zn‐deficient soils. The preference for expressing analytical results on a volume rather than weight basis is discussed. Based on a review of literature relating to the M3 extractant, the following critical M3 soil test values are tentatively recommended for maize on upland Malawi soils: Ca, 50 mg/dm³; Mg, 75 mg/dm³ and Mg:Ca ratio >0.067; K, 70 mg/dm³; P, 20 mg/dm³; Zn, 1.0 mg/dm³; and Cu, 0.5 mg/dm³. These suggested values should not preclude in‐country correlation studies. Because the M3 procedure is well correlated with the AA, DPTA, and Bray 1 methods, and because it is a rapid procedure, the M3 method can be highly recommended as a replacement for the three current procedures for Malawi upland soils. Caution is advised in extending the results to Malawi lowland soils, which are characterized by higher pH values.     

Effect of treated sewage water on vegetative and reproductive growth of date palm

Abstract

The effect of treated sewage water on the vegetative and reproductive growth of date palms was assessed. Leaves and fruits samples were collected from locations irrigated with treated sewage (TSW), desalinised, and well water. Samples were analysed for their calcium (Ca), magnesium (Mg), iron (Fe), lead (Pb), copper (Cu), and zinc (Zn) content by atomic absorption spectro‐photometry and for sodium (Na) and potassium (K) by flame photometry. The Mg, Fe, and Zn content of fruits and Na in the leaves were not found to be significantly different. Treated sewage water from University campus utilities significantly increased the Na, K, and Cu and reduced Ca in leaves and Zn in fruits of date palms. But no significant effect was observed on the K, Ca, Mg, and Na contents in fruits of the same palms. The different concentrations of Ca, Mg, Fe, and Zn in the fruits of date palms grown along the same TSW line were attributed to variations in the soil; however, those in Pb content of leaves could be attributed to motor vehicle combustion. The general trend indicated that fruits contained higher K, Na, and Fe contents, but lower Ca, Mg, Cu, Zn, and Pb contents than the leaves. Furthermore, leaves of date palms irrigated with desalinised and well water contained higher Ca and Zn, but lower K, Mg, Na, Cu, Fe, and Pb contents than those of palms irrigated with treated sewage water. Desalinised water reduced the K, Ca, Na, and Zn contents, but it increased the Mg, Fe, Cu, and Pb content of leaves compared to well water. None of the examined metals were found to reach toxic level to man or plant.     

施肥结构对砂质潮土中微量营养元素空间变化的影响

本文通过长期定位施肥试验 ,分析了不同施肥结构对砂质潮土交换性钙、镁及有效硫、锌、锰、铜、铁等在 0～ 1 2 0cm土体中空间分布变化的影响 .结果表明 ,磷肥明显提高土壤交换性钙的含量 ,而有机肥与氮肥对土壤钙含量无明显影响 .但有机肥显著增加土壤交换性镁含量 ,各层镁含量与有机肥用量呈显著或极显著正相关 ,磷肥同样对土壤镁有提高作用 ,但氮肥无论是否与有机肥配施均降低了土壤各层交换性镁含量 .土壤 0～ 4 0cm有效锌、锰、铁均随有机肥增加而增加 ,并与有机肥用量呈极显著正相关 .而化肥无论是否与有机肥配施均降低土壤有效锌含量 ,但却增加了有效铁含量 .氮肥单施降低土壤有效锰含量 .在无有机肥情况下 ,施磷提高土壤有效铁含量 ,而在施有机肥条件下磷肥则降低耕层有效铁含量 .磷肥只在单施化肥时增加土壤有效锰含量     

Mycorrhizal colonization and nutrition of wheat and sweet corn grown in manure‐treated and untreated topsoil and subsoil

Dry bean yields (Phaseolus vulgaris L.) were raised to similar levels as the topsoil by manure application to eroded or leveled Portneuf silt loam soil (coarse‐silty mixed mesic Durixerollic Calciorthid). Only soil organic matter and zinc (Zn) content of leaf tissue were correlated with improved yields. Manure application increased mycorrhizal colonization and Zn uptake in pot experiments with dry bean which would explain the increased yields in the field. A field study was conducted to see if similar effects of manure and mycorrhizal colonization could be observed in field grown spring wheat (Triticum aestivum L.) and sweet corn (Zea mays L.). This study was conducted on existing experiments established in the spring of 1991 at the USDA‐ARS farm in Kimberly, Idaho, to study crop rotation/organic matter amendment treatments on exposed subsoils and focused on mycorrhizal colonization as related to topsoils and subsoils treated with conventional fertilizer (untreated) or dairy manure. Mycorrhizal root colonization was higher with untreated than with manure‐treated wheat and sweet corn. Root colonization was also higher in subsoil than in topsoil for wheat, but there were no differences between soils for sweet corn. Shoot Zn and manganese (Mn) concentrations generally increased with increased root colonization for both species (except between soils with corn Mn contents). Wheat shoot potassium (K) concentration was increased by manure application, but the affect declined with time, was the opposite of colonization and was not observed with sweet com. Phosphorus (P), calcium (Ca), magnesium (Mg), iron (Fe), and copper (Cu) concentrations either were not influenced or were erratically affected by mycorrhizal colonization. Yields of wheat were highest for manure‐treated subsoil and topsoil compared to untreated soils. Mycorrhizal colonization was different between conventional and manure‐treated soils and between topsoil and subsoil and these differences increased Zn and Mn uptake, but they did not explain the improvement in wheat yields obtained with manure application.     

Effect of Organic Materials on Yields and Nutrient Accumulation of Wheat

ABSTRACT

This experiment was conducted under greenhouse conditions using a sandy clay loam treated with garbage and mushroom composts, cattle and chicken manures, or municipal sludge at rates of 0, 30, or 60 ton ha^?1. The organic materials were applied to the pots and incubated for 15 d. The soil samples were watered at field capacity. In this experiment, wheat (Triticum aestivum L.) was used as a test crop. At the end of the experiment, it was found that treating sandy clay loam with the organic materials increased plant total and grain yields, protein content, 1000-kernel weight, number of grains in spike, and accumulation of nitrogen (N), phosphorus (P), potassium (K), iron (Fe), zinc (Zn), and manganese (Mn) by wheat compared with the control treatment, depending on the organic material applications. Thus, the increases were found to be statistically significant (P ≤ 0.05). Among the types of organic materials, the sewage sludge was the most effective material in increasing N, P, K, Fe, Zn, and Mn content of leaf, grain, and stem samples of the wheat plant. It was followed by mushroom compost and cattle manure. Based on the results, sewage sludge and garbage compost are suggested for use as an amendment for the soil studied. Comparing the beneficial effects of the organic materials applied for improving plant growth and nutrient accumulation, the materials can be arranged in the following descending order: municipal sludge > chicken manure > cattle manure > garbage compost > mushroom compost. It is suggested that recycling of organic materials for agricultural usage as an organic-matter resource is an alternative, organic fertilization option in Turkey.     

Comparison of routine soil tests and EPA method 3050 as extractants for heavy metals in Delaware soils

Abstract

Agricultural use of sewage sludges can be limited by heavy metal accumulations in soils and crops. Information on background levels of total heavy metals in soils and changes in soil metal content due to sludge application are; therefore, critical aspects of long‐term sludge monitoring programs. As soil testing laboratories routinely, and rapidly, determine, in a wide variety of agricultural soils, the levels of some heavy metals and soil properties related to plant availability of these metals (e.g. Cu, Fe, Mn, Zn, pH, organic matter, texture), these labs could participate actively in the development and monitoring of environmentally sound sludge application programs. Consequently, the objective of this study was to compare three soil tests (Mehlich 1, Mehlich 3, and DTP A) and an USEPA approved method for measuring heavy metals in soils (EPA Method 3050), as extractants for Cd, Cu, Ni, Pb and Zn in representative agricultural soils of Delaware and in soils from five sites involved in a state‐monitored sludge application program.

Soil tests extracted less than 30% of total (EPA 3050) metals from most soils, with average percentages of total metal extracted (across all soils and metals) of 15%, 32%, and 11% for the Mehlich 1, Mehlich 3, and DTPA, respectively. Statistically significant correlations between total and soil test extractable metal content were obtained with all extractants for Cu, Pb, and Zn, but not Cd and Ni. The Mehlich 1 soil test was best correlated with total Cu and Zn (r=0.78***, 0.60***, respectively), while the chelate‐based extractants (DTPA and Mehlich 3) were better correlated with total Pb (r=0.85***, 0.63***). Multiple regression equations for the prediction of total Cu, Ni, Pb, and Zn, from soil test extractable metal in combination with easily measured soil properties (pH, organic matter by loss on ignition, soil volume weight) had R² values ranging from 0.41*** to 0.85***, suggesting that it may be possible to monitor, with reasonable success, heavy metal accumulations in soils using the results of a routine soil test.     

Erratum: Chemical composition of cabbage (Brassica oleracea L. var. capitata) grown on acid sulfate soils

The purpose of this study was to investigate the influence of soil geochemistry on the concentrations of Ca, K, Mg, P, Co, Ni, Zn, Mn, Cu, and Fe in cabbage (Brassica oleracea L. var. capitata) grown on acid sulfate (AS) soils in Western Finland. A total of 11 topsoil (0–20 cm) and corresponding cabbage samples and three whole‐soil profiles (≈ 0–260 cm) were collected on three agricultural fields. The concentrations of Co and Zn in cabbage were correlated with the NH₄Ac‐extractable (easily available) concentrations in the topsoil, indicating that the uptake of these elements in cabbage is largely governed by soil geochemistry. Yet, the concentrations of Co and Zn in cabbage were not in general elevated relative to that of Finnish average values, although some AS soils showed enriched concentrations of these metals in the soil and cabbage. Significant geochemical differences (e.g., oxidation depth, organic‐matter and S content, pH) were observed among the studied AS soils, while, on the other hand, the concentrations of Ca, K, Mg, P, Ni, Mn, Cu, and Fe in cabbage were relatively similar. The hydroxylamine‐extractable concentrations of these elements in the topsoil were not correlated to those in cabbage, suggesting that uptake is not governed by the oxide‐bound fraction of these elements in the soil. Similarly, the easily available concentrations of Ca, P, Ni, Mn, Cu, and Fe in the topsoil were not correlated to those in cabbage, indicating that uptake is independent of the easily available concentrations in the soil. Hence, it is suggested that cabbage can regulate and thus optimize its concentrations of Ca, P, Ni, Mn, Cu, and Fe. Oxidation depth affected neither the easily available concentrations of Co, Ni, Zn, and Mn in the topsoil nor the concentrations in cabbage. However, the subsoil with a lower oxidation depth, which is to a smaller extent affected by leaching, may partly be enriched in these metals. Nevertheless, these showed no increased concentrations in cabbage. Based on these findings, it is suggested that the large amounts of metals mobilized in AS soils are easily lost to drains, subsequently contaminating nearby waterways and estuaries whereas they are only partly enriched in cabbage and other previously studied crops (oat).     

Application of High Copper and Zinc Compost and Its Effects on Soil Properties and Growth of Barley

Abstract

A compost of high copper (Cu) and zinc (Zn) content was added to soil, and the growth of barley (Hordeum vulgare L.) was evaluated. Four treatments were established, based on the addition of increasing quantities of compost (0, 2, 5, and 10% w/w). Germination, plant growth, biomass production, and element [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), iron (Fe), Cu, manganese (Mn), and Zn] contents of soil and barley were determined following a 16‐week growing period. Following harvesting of the barley, analysis of the different mixtures of soil and compost was performed. Micronutrient contents in soils as affected by compost additions were determined with diethylene–triamine–pentaacetic acid (DTPA) (Cu, Mn, Fe, and Zn) or ammonium acetate [Ca, Na, Mg, K, cation exchange capacity (CEC)] extractions, and soils levels were compared to plant uptake where appropriate. Increasing rates of compost had no affect on Ca, Mg, or K concentration in barley. Levels of Cu, Zn, Mn, and Na, however, increased with compost application. High correlations were found for DTPA‐extractable Cu and Zn with barley head and shoot content and for Mn‐DTPA and shoot Mn content. Ammonium acetate–extractable Na was highly correlated with Na content in the shoot. High levels of electrical conductivity (EC), Cu, Zn, and Na may limit utilization of the compost.     

The soil solution in a soil treated with digested sewage sludge

Toxic trace metals may percolate to the ground water from sewage sludge disposed onto land. Analyses are presented of the soil solution from a slightly acid loamy soil treated 7 years earlier with single applications of digested sewage sludge in amounts equivalent to 0, 150 & 330 t dry matter ha⁻¹
These very heavy dressings correspond to 2 & 4.5 times the recommended 30–year limit. Samples of soil and soil solution from four depths to 80 cm were analysed for Al, B, Ba, Ca, Cl, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, S, Sr, V, Zn, together with the OM of the soil, and the pH, alkalinity, dissolved organic carbon, and absorbance at 350 nm of the solutions.
These very heavy sludge applications were apparently still releasing substantial quantities of NO₃, and some SO₄ even after 7 years. Nitrate, SO₄, Mg, Ca, Sr, B, and possibly Ba are still moving through the profile, possibly to the ground water. Solution concentrations of Cu and Zn are considerably higher at all depths than those in the untreated plot, but they fall off sharply with depth. It is unlikely that any Cu or Zn is now reaching the ground water.
The paper also presents a set of published solution analyses for soils, sludge–treated soils and digested sludge, as a basis for further studies.     

间作五指毛桃土壤和根主要中微量元素含量及其相关性

为了解在成龄胶园间作的五指毛桃根际与非根际土壤及其根中主要中、微量元素含量情况，测定了实验区根际与非根际土壤各30个和对应五指毛桃根的钙、镁、铁、锰、铜和锌含量，分析了两者之间的关系，并评价了根际与非根际土壤中、微量元素丰缺状况。结果表明，非根际土壤钙、镁、铁、锰含量的平均值都高于根际土壤的，而铜、锌含量的平均值都低于根际土壤的。土壤钙、镁含量80%以上处于缺水平，而铁、锰含量处于丰或很丰水平，铜和锌含量处于适中水平。五指毛桃根际与非根际土壤中、微量元素存在空间上的广泛变异。五指毛桃根中、微量元素的平均值从大到小的排序是钙>镁>锰>铁>锌>铜。土壤中、微量元素与五指毛桃根中相对应的中、微量元素的相关性不强，且表现复杂。本研究结果揭示，在成龄胶园间作五指毛桃应当适量施用钙肥、镁肥和喷施一些铜元素叶面肥，并实行科学施肥，减少养分淋失。     

Extractability and plant uptake of heavy metals in alum shale soils

Abstract

Fifty soil samples (0–20 cm) with corresponding numbers of grain, potatoes, cabbage, and cauliflower crops were collected from soils developed on alum shale materials in Southeastern Norway to investigate the availability of [cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), and manganese (Mn)] in the soil and the uptake of the metals by these crops. Both total (aqua regia soluble) and extractable [ammonium nitrate (NH₄NO₃) and DTPA] concentrations of metals in the soils were studied. The total concentration of all the heavy metals in the soils were higher compared to other soils found in this region. Forty‐four percent of the soil samples had higher Cd concentration than the limit for application of sewage sludge, whereas the corresponding values for Ni, Cu, and Zn were 60%, 38%, and 16%, respectively. About 70% the soil samples had a too high concentration of one or more of the heavy metals in relation to the limit for application of sewage sludge. Cadmium was the most soluble of the heavy metals, implying that it is more bioavailable than the other non‐essential metals, Pb and Ni. The total (aqua regia soluble) concentrations of Cd, Cu, Zn, and Ni and the concentrations of DTPA‐extractable Cd and Ni were significantly higher in the loam soils than in the sandy loam soils. The amount of NH₄NCyextractable metals did not differ between the texture classes. The concentrations of DTPA‐extractable metals were positively and significantly correlated with the total concentrations of the same metals. Ammonium nitrate‐extractable metals, on the other hand, were not related to their total concentrations, but they were negatively and significantly correlated to soil pH. The average concentration of Cd (0.1 mg kg^‐1 d.w.) in the plants was relatively high compared to the concentration previously found in plants grown on the other soils. The concentrations of the other heavy metals Cu, Zn, Mn, Ni, and Pb in the plants were considered to be within the normal range, except for some samples with relatively high concentrations of Ni and Mn (0–11.1 and 3.5 to 167 mg kg‘¹ d.w., respectively). The concentrations of Cd, Cu, Zn, Ni, and Mn in grain were positively correlated to the concentrations of these respective metals in the soil extracted by NH₄NO₃. The plant concentrations were negatively correlated to pH. The DTPA‐extractable levels were not correlated with plant concentration and hence DTPA would not be a good extractant for determining plant availability in these soils.     

Impacts of biochar and processed poultry manure,applied to a calcareous soil,on the growth of bean and maize

Direct use of poultry manure on agricultural lands may cause environmental concerns, so there is a need to establish the suitability of the application of biochar derived from poultry manure for calcareous soil chemical properties and plant growth. The purpose of this study was to evaluate the effects of processed poultry manure (0, 5, 10 and 20 g/kg) and its biochar (0, 2.5, 5, 10 and 20 g/kg) on soil chemical properties of a calcareous soil and growth of bean (Phaseolus vulgaris) and maize (Zea mays) plants. In the incubation experiment, both processed poultry manure (PPM) and biochar decreased pH and the concentration of plant‐available Fe of soil but increased plant‐available P, Zn, Cu and Mn concentrations. PPM and biochar increased the concentrations of exchangeable cations (K, Ca and Mg) in soil. PPM and biochar applications increased the growth of maize and bean plants. PPM and biochar resulted in increased concentrations of N, P, K, Ca, Fe, Zn, Cu and Mn in bean plants. In maize plants, PPM and biochar applications increased the N, P, K, Zn, Cu and Mn but decreased the Ca and Mg concentrations. Results of this study reveal that poultry manure biochar can be used effectively for agricultural purposes.