Application of different foliar iron fertilizers for enhancing the growth and antioxidant capacity of rice and minimizing cadmium accumulation

Environmental Science and Pollution Research - Iron (Fe) fertilizer can reduce cadmium (Cd) uptake and toxicity in rice, but the underlying mechanisms of Cd mitigation by different fertilizers are...     

Cadmium uptake by tobacco as affected by liming, N form, and year of cultivation

Tobacco is able to accumulate cadmium and reduction of cadmium content can reduce health hazards to smokers. Soil pH and form of N fertilizers are among the factors affecting Cd uptake by tobacco. This hypothesis was tested in an acid soil in northern Greece by a four year field experiment. The variability of Cd uptake by tobacco was attributed to the variation of soil Cd availability as affected by soil pH. Liming with 3000 kg Ca(OH)(2) ha(-1) increased soil pH by 0.8 units and decreased extractable with DTPA soil and leaf Cd by 40% and 35%, respectively. The ammonium fertilizer caused the opposite, but weaker, effects. Liming reduced soil Cd more in the ammonium treatment than in nitrate or combined N treatments. The year of cultivation strongly affected soil and leaf Cd. Four years after tobacco cultivation, soil pH was reduced by 0.5 units, whereas soil and leaf Cd reduction was more than 60% in the limed treatments. Liming affected Cd uptake only in the first three years of cultivation.     

Remediation of cadmium-contaminated paddy soils by washing with calcium chloride: verification of on-site washing

We developed a new, three-step soil-wash method to remediate Cd-contaminated paddy fields. The method comprises (1) chemically washing the field soil with a CaCl2 solution; (2) washing the treated soil with water to eliminate residual Cd and CaCl2; and (3) on-site treatment of wastewater using a portable wastewater treatment system. Cd concentrations in the treated water were below Japan's environmental quality standard (0.01 mg Cd L-1), and the removal of Cd from the exchangeable fraction was 55% and from the acid-soluble fraction 15%. While soil fertility properties were affected by the soil washing, adverse effects were not crucial and could be corrected. The washing had no affect on rice growth, and reduced the average Cd concentration in rice grains by about two-thirds compared to a control plot. These results confirmed the effectiveness of the soil-wash method in remediating Cd-contaminated paddy fields.     

Effect of phosphate fertilizer application on phosphorus (P) losses from paddy soils in Taihu Lake Region. I. Effect of phosphate fertilizer rate on P losses from paddy soil

A field plot study was conducted on two types of paddy soils in the Taihu Lake Region, during the rice season of year 2000 in order to assess phosphorus (P) losses by runoff and vertical leaching, which are considered the two main pathways of P movement from paddy soil into its surrounding water course. Commercial NPK compound fertilizer and single superphosphate fertilizer were applied to furnish 0, 30, 150, and 300 kg applied P ha m(-2). The experiments consisted of three replicates of each treatment in Changshu site and four replicates in Anzhen site, with a plot size of 5 x 6 m2 in a randomized block. Results revealed that the average concentration range for total P (TP) in runoff was 1.857-7.883, 1.038-5.209, 0.783-1.255 and 0.572-0.691 mg P l(-1) respectively for P300, P150, P30 and P0 in Anzhen, while it was 2.431-2.449, 1.578-1.890, 1.050-1.315 and 0.749-0.941 mg P l(-1) respectively in Changshu. In all treatments, particulate P (PP) represented a major portion of the TP lost in runoff, it was 80% in Anzhen, and it was even more (>90%) in Changshu. Phosphate fertilizer treatments significantly affected P concentrations and P loads in the runoff. The mean concentration and average seasonal TP load from the P150 plots were 1.809 mg P l(-1) and 395 g P ha m(-2) season(-1) respectively, and lower than that from the P300 plots (2.957 mg P l(-1) and 652 g P ha m(-2) season(-1)). These were obviously higher than from the P30 (0.761 mg P l(-1) and 221 g P ha m(-2) season(-1)) and P0 (0.484 mg P l(-1) and 146 g P ha m(-2) season(-1)) respectively. There was no significant difference found between the P30 and the P0 in both sites. Under usual P application rate, there were total 31.7 and 20.6 tones P removed by runoff from permeable (Anzhen site) and waterlogged (Changshu site) paddy soils in the southern Jiangsu region (major part of the TLR) in the rice season of the year 2000. But if the P application rate is unusual high, or the Olsen P in soil accumulates to above a certain level, then this could sharply increase in the future. The average concentration of molybdate reactive phosphorus (MRP) in the vertical leachate from the four different P treatments ranged from 0.058 to 0.304 mg P l(-1) in Anzhen and from 0.048 to 0.394 mg P l(-1) in Changshu. P application rate significantly affected the MRP concentration at each depth in both sites, except for the 90 cm in Anzhen. The average MRP loads during the rice season moved by vertical leaching from the four treatments ranged from 163 to 855 g P ha m(-2) season(-1) in Anzhen and 208-1,825 g P ha m(-2) season(-1) in Changshu. Vertical leachate movement does not necessarily mean that it moves towards surface water and contaminate the watercourses in this flat plain paddy soil region, it does, however, imply that P can move down from surface layers of soil to deeper levels.     

Municipal waste compost as an alternative to cattle manure for supplying potassium to lowland rice

The importance of the use of potassium in agriculture is increasing in South Asia for making most productive use of the nutrient in terms of economic returns. Nutrient supply traditionally by cattle manure is constrained by its insufficient availability. Municipal waste compost may be an alternative source of nutrient supplements. Field experiments were conducted at the Experimental Farm of Calcutta University, West Bengal, India during the wet seasons of 1997, 1998 and 1999 on flooded lowland rice. Potassium fractions in municipal waste compost and cattle manure were determined by sequential extraction and also the potassium uptake by rice to compare the effectiveness of municipal waste compost with traditional manure. Potassium was significantly bound to the organic matter in municipal waste compost. Potassium uptake by rice grain and straw increased significantly with the combined application of organics and fertilizers and it was higher in grain than in straw. Water-soluble and non-exchangeable potassium contents of municipal waste compost and cattle manure were highly correlated with the uptake of potassium by straw and grain. Exchangeable and residual potassium were also significantly correlated with the uptake of potassium by straw and grain of rice. Much higher uptake of K in rice straw and rain resulted from applying the manures in conjunction with fertilizers than when applied singly.     

Cadmium stress in rice: toxic effects,tolerance mechanisms,and management: a critical review

Cadmium (Cd) is one of the main pollutants in paddy fields, and its accumulation in rice (Oryza sativa L.) and subsequent transfer to food chain is a global environmental issue. This paper reviews the toxic effects, tolerance mechanisms, and management of Cd in a rice paddy. Cadmium toxicity decreases seed germination, growth, mineral nutrients, photosynthesis, and grain yield. It also causes oxidative stress and genotoxicity in rice. Plant response to Cd toxicity varies with cultivars, growth condition, and duration of Cd exposure. Under Cd stress, stimulation of antioxidant defense system, osmoregulation, ion homeostasis, and over production of signaling molecules are important tolerance mechanisms in rice. Several strategies have been proposed for the management of Cd-contaminated paddy soils. One such approach is the exogenous application of hormones, osmolytes, and signaling molecules. Moreover, Cd uptake and toxicity in rice can be decreased by proper application of essential nutrients such as nitrogen, zinc, iron, and selenium in Cd-contaminated soils. In addition, several inorganic (liming and silicon) and organic (compost and biochar) amendments have been applied in the soils to reduce Cd stress in rice. Selection of low Cd-accumulating rice cultivars, crop rotation, water management, and exogenous application of microbes could be a reasonable approach to alleviate Cd toxicity in rice. To draw a sound conclusion, long-term field trials are still required, including risks and benefit analysis for various management strategies.     

Chemical methods and phytoremediation of soil contaminated with heavy metals

The effects of chemical amendments (calcium carbonate (CC), steel sludge (SS) and furnace slag (FS)) on the growth and uptake of cadmium (Cd) by wetland rice, Chinese cabbage and wheat grown in a red soil contaminated with Cd were investigated using a pot experiment. The phytoremediation of heavy metal contaminated soil with vetiver grass was also studied in a field plot experiment. Results showed that treatments with CC, SS and FS decreased Cd uptake by wetland rice, Chinese cabbage and wheat by 23-95% compared with the unamended control. Among the three amendments, FS was the most efficient at suppressing Cd uptake by the plants, probably due to its higher content of available silicon (Si). The concentrations of zinc (Zn), lead (Pb) and Cd in the shoots of vetiver grass were 42-67%, 500-1200% and 120-260% higher in contaminated plots than in control, respectively. Cadmium accumulation by vetiver shoots was 218 g Cd/ha at a soil Cd concentration of 0.33 mg Cd/kg. It is suggested that heavy metal-contaminated soil could be remediated with a combination of chemical treatments and plants.     

Role of blue green algae biofertilizer in ameliorating the nitrogen demand and fly-ash stress to the growth and yield of rice (Oryza sativa L.) plants

Rice is a major food crop throughout the world; however, accumulation of toxic metals and metalloids in grains in contaminated environments is a matter of growing concern. Field experiments were conducted to analyze the growth performance, elemental composition (Fe, Si, Zn, Mn, Cu, Ni, Cd and As) and yield of the rice plants (Oryza sativa L. cv. Saryu-52) grown under different doses of fly-ash (FA; applied @ 10 and 100 tha(-1) denoted as FA(10) and FA(100), respectively) mixed with garden soil (GS) in combination with nitrogen fertilizer (NF; applied @ 90 and 120 kg ha(-1) denoted as NF(90) and NF(120), respectively) and blue green algae biofertilizer (BGA; applied @ 12.5 kg ha(-1) denoted as BGA(12.5)). Significant enhancement of growth was observed in the plants growing on amended soils as compared to GS and best response was obtained in amendment of FA(10)+NF(90)+BGA(12.5). Accumulation of Si, Fe, Zn and Mn was higher than Cu, Cd, Ni and As. Arsenic accumulation was detected only in FA(100) and its amendments. Inoculation of BGA(12.5) caused slight reduction in Cd, Ni and As content of plants as compared to NF(120) amendment. The high levels of stress inducible non-protein thiols (NP-SH) and cysteine in FA(100) were decreased by application of NF and BGA indicating stress amelioration. Study suggests integrated use of FA, BGA and NF for improved growth, yield and mineral composition of the rice plants besides reducing the high demand of nitrogen fertilizers.     

Nitrate leaching in an Andisol treated with different types of fertilizers

Nitrate (NO3) leaching was studied in an Andisol treated with four N fertilizers (SC: swine compost, CU: coated urea, AN: ammonium N, or NF: no fertilizer) for 7 years. Sweet corn (Zea mays L.) was grown in summer, followed by Chinese cabbage (Brassica rapa L. var. amplexicaulis) or cabbage (Brassica oleracea L. var. capitata) in autumn each year. In chemical fertilizer plots treated with AN or CU, NO(3)-N concentrations in soil water at 1-m depth increased markedly in the summer of the second year and fluctuated between 30 and 60 mg l(-1). In the SC plot, NO(3)-N concentration started increasing in the fourth year, reaching the same level as in the AN and CU plots in the late period of the experiment. In the NF plot, NO(3)-N concentration was about 10 mg l(-1) for the first 4 years and decreased to 5 mg l(-1). The potential NO(3)-N concentrations by an N and water balance equation satisfactorily predicted NO(3)-N concentration in the AN and CU plots, but substantially overestimated that in the SC plot, presumably because a large portion of N from SC first accumulated in soil in the organic form. Our results indicate that, under the Japanese climate (Asian monsoon), excessive N from chemical fertilizers applied to Andisols can cause substantial NO3 leaching, while compost application is promising to establish high yields and low N leaching during a few years but would cause the same level of NO3 leaching as in chemically fertilized plots over longer periods.     

Estimation of methane and nitrous oxide emission from paddy fields and uplands during 1990-2000 in Taiwan

To investigate the greenhouse gases emissions from paddy fields and uplands, methane and nitrous oxide emissions were estimated from local measurement and the IPCC guidelines during 1990-2000 in Taiwan. Annual methane emission from 182,807 to 242,298 ha of paddy field in the first crop season ranged from 8,062 to 12,066 ton, and it was between 16,261 and 25,007 ton for 144,178-211,968 ha in the second crop season with local measurement. The value ranged from 12,132 to 17,465 ton, and from 16,046 to 24,762 ton of methane in the first and second crop season with the IPCC guidelines for multiple aeration treatments, respectively. Annual nitrous oxide emission was between 472 and 670 ton and between 236 and 359 ton in the first and second crop season, respectively. Methane and nitrous oxide emissions from uplands depend on crop, growth season, fertilizer application and environmental conditions. Annual methane emission from upland crops, vegetable, fruit, ornamental plants, forage crops and green manure crops was 138-252, 412-460, 97-100, 3-5, 4-5 and 3-51 ton, respectively. Annual nitrous oxide emission was 1,080-1,976, 1,784-1,994, 2,540-2,622, 31-54, 43-53 and 38-582 ton, respectively. Annual nitrous oxide emission ranged from 91 to 132 ton for 77,593-11,2095 ton of nitrogen-fixing crops, from 991 to 1,859 ton for 3,259,731-6,183,441 ton of non-nitrogen-fixing crops, and from 1.77 to 2.22 Gg for 921,169-1,172,594 ton of chemical fertilizer application. In addition, rice hull burning emitted 19.3-24.2 ton of methane and 17.2-21.5 ton of nitrous oxide, and corn stalk burning emitted 2.1-4.2 ton of methane and 1.9-3.8 ton of nitrous oxide. Methane emission from the agriculture sector was 26421-37914 ton, and nitrous oxide emission was 9810-11,649 ton during 1990-2000 in Taiwan. Intermittent irrigation in paddy fields reduces significantly methane emission; appropriate application of nitrogen fertilization and irrigation in uplands and paddy fields also decreases nitrous oxide emission.     

Correlations between cadmium and mineral nutrients in absorption and accumulation in various genotypes of rice under cadmium stress

The absorption and accumulation of Cd2+, Fe3+, Zn2+, Mn2+, Cu2+ and Mg2+ in the roots and leaves of 20 rice cultivars (Oryza sativa L.) with different genotypes under cadmium (Cd) stress were investigated with pot experiments. The results showed that there existed significant differences among the rice cultivars in the contents of six mineral elements in both roots and leaves at both heading and ripening periods. The statistical analysis showed that, for their contents in roots, significant and positive correlations between Cd2+ and Fe3+, Cd2+ and Zn2+, Cd2+ and Mn2+, Cd2+ and Cu2+ existed, but no significant correlation between Cd2+ and Mg2+, at the two periods. In the leaves, Cd also showed significant and positive correlations with Fe3+, Zn2+ and Cu2+ at the both periods, but a significant and negative correlation with Mn2+ and no significant correlation with Mg2+ at heading, a significant and positive correlation with Mg2+ and no significant correlation with Mn2+ at ripening. These results suggested that there were cooperative absorption between Cd2+ and Fe3+, Mn2+, Cu2+, Mn2+ in rice plants. Genotypic differences in Cd uptake and translocation among the rice cultivars suggested that paddy field of some rice cultivars may be irrigated with partially treated sewage water.     

The composition,leaching, and sorption behavior of some alternative sources of phosphorus for soils

Concerns about the sustainability of inorganic fertilizers necessitate the characterization of alternative P source materials for agronomic P-efficiencies and P losses via leaching. Firstly, this study examined nutrient compositions including P speciation of seven soil amendments: sewage sludge (SS), anaerobic digestate (AD), green compost (GC), food waste compost (FWC), chicken manure (CM), biochar, and seaweed. Secondly, soil P leaching and availability was studied on a subset of four materials (SS, AD, GC, and CM). Sorption of extracts onto columns of a test soil showed strong P retention for SS and compost, but weak P sorption for CM and especially AD, suggesting short-term leaching risks for soil applied AD. Limited P desorption with water or citrate indicated sorbed P was strongly fixed, potentially limiting crop availability. These data indicate that variation in P forms and environmental behavior should be understood to maximize P usage, but minimize leaching and soil P accumulation. Hence, different alternative P source materials need differing recommendations for their agronomic management.     

Model development for nutrient loading estimates from paddy rice fields in Korea

A field experiment was performed to evaluate water and nutrient balances in paddy rice culture operations during 2001-2002. The water balance analysis indicated that about half (50-60%) of the total outflow was lost by surface drainage, with the remainder occurring by evapotranspiration (490-530 mm). The surface drainage from paddy fields was mainly caused by rainfall and forced-drainage, and in particular, the runoff during early rice culture periods depends more on the forced-drainage due to fertilization practices. Most of the total phosphorus (T-P) inflow was supplied by fertilization at transplanting, while the total nitrogen (T-N) inflow was supplied by the three fertilizations, precipitation. and from the upper paddy field, which comprised 13-33% of the total inflow. Although most of the nutrient outflow was attributed to plant uptake. nutrient loss by surface drainage was substantial, comprising 20% for T-N and 10% for T-P. Water and nutrient balances indicate that reduction of surface drainage from paddy rice fields is imperative for nonpoint source pollution control. The simplified computer model, PADDIMOD, was developed to simulate water and nutrient (T-N and T-P) behavior in the paddy rice field. The model predicts daily ponded water depth, surface drainage, and nutrient concentrations. It was formulated with a few equations and simplified assumptions, but its application and a model fitness test indicated that the simulation results reasonably matched the observed data. It is a simple and convenient planning model that could be used to evaluate BMPs of paddy rice fields alone or in combination with other complex watershed models. Application of the PADDIMOD to other paddy rice fields with different agricultural environments might require further calibration and validation.     

Effects of rapeseed residue on lead and cadmium availability and uptake by rice plants in heavy metal contaminated paddy soil

Rapeseed (Brassica napus L.) has been cultivated for biodiesel production worldwide. Winter rapeseed is commonly grown in the southern part of Korea under a rice-rapeseed double cropping system. In this study, a greenhouse pot experiment was conducted to assess the effects of rapeseed residue applied as a green manure alone or in combinations with mineral N fertilizer on Cd and Pb speciation in the contaminated paddy soil and their availability to rice plant (Oryza sativa L.). The changes in soil chemical and biological properties in response to the addition of rapeseed residue were also evaluated. Specifically, the following four treatments were evaluated: 100% mineral N fertilizer (N100) as a control, 70% mineral N fertilizer + rapeseed residue (N70 + R), 30% mineral N fertilizer + rapeseed residue (N30 + R) and rapeseed residue alone (R). The electrical conductivity and exchangeable cations of the rice paddy soil subjected to the R treatment or in combinations with mineral N fertilizer treatment, N70 + R and N30 + R, were higher than those in soils subjected to the N100 treatment. However, the soil pH value with the R treatment (pH 6.3) was lower than that with N100 treatment (pH 6.9). Use of rapeseed residue as a green manure led to an increase in soil organic matter (SOM) and enhanced the microbial populations in the soil. Sequential extraction also revealed that the addition of rapeseed residue decreased the easily accessible fraction of Cd by 5-14% and Pb by 30-39% through the transformation into less accessible fractions, thereby reducing metal availability to the rice plant. Overall, the incorporation of rapeseed residue into the metal contaminated rice paddy soils may sustain SOM, improve the soil chemical and biological properties, and decrease the heavy metal phytoavailability.     

Long-term effects of fertilization on the forms and availability of soil phosphorus in rice paddy

The changes in total P accumulation and P compounds with time in the plough layer in a paddy soil in southern Korea were investigated in relation to the continuous application of chemical fertilizers (NPK), straw based compost (Compost), combination these two (NPK+Compost) for 31 years. Continuous fertilization increased the total and inorganic P contents in plough layers. In NPK, inorganic P fraction did not change with time, but organic P content increased significantly. Long-term application of chemical fertilizer together with compost accelerated the decrease in the organic P fraction, presumably due to promoting microbial activity in the plow layer, and then increased significantly inorganic P fraction. Compost application decreased the residual P and Fe-P fractions and then increased inorganic P fraction, in spite of continuous compost application. Increase in total, inorganic and extractable P with time may be closely related to the increase in the availability of accumulated P for rice growth.     

Effects of aqueous Moringa oleifera leaf extract on growth performance and accumulation of cadmium in a Thai jasmine rice—Khao Dawk Mali 105 variety

Environmental Science and Pollution Research - The contamination of paddy fields and rice grains by cadmium (Cd) adversely affects human health. Thus, many approaches have been proposed to reduce...     

The influence of long-term fertilization on cadmium (Cd) accumulation in soil and its uptake by crops

Continuous application of organic and inorganic fertilizers can affect soil and food quality with respect to heavy metal concentrations. The risk of cadmium (Cd) contamination in a long-term (over 20 years) experimental field in North China with an annual crop rotation of winter wheat and summer maize was investigated. The long-term experiment had a complete randomized block design with seven fertilizer treatments and four replications. The seven fertilizer treatments were (1) organic compost (OM), (2) half organic compost plus half chemical fertilizer (OM?+?NPK), (3) NPK fertilizer (NPK), (4–6) chemical fertilizers without one of the major nutrients (NP, PK, and NK), and (7) an unamended control (CK). Soil samples from 0 to 20 cm were collected in 1989, 1999, and 2009 to characterize Cd and other soil properties. During the past 20 years, various extents of Cd accumulation were observed in the soil, and the accumulation was mainly affected by atmospheric dry and wet deposition and fertilization. In 2009, the average Cd concentration in the soil was 148?±?15 μg kg^?1 and decreased in the order of NPK?≈?OM?+?NKP?≈?PK?>?NP?≈?NK?>?OM?≈?CK. Sequential extraction of Cd showed that the acid-soluble fraction (F1, 32?±?7 %) and the residual fraction (F4, 31?±?5 %) were the dominant fractions of Cd in the soil, followed by the reducible fraction (F2, 22?±?5 %) and oxidizable fraction (F3, 15?±?6 %). The acid-soluble Cd fraction in the soil and Cd accumulation in the crops increased with soil plant available K. Fraction F3 was increased by soil organic C (SOC) and crop yields, but SOC reduced the uptake of soil Cd by crops. The long-term P fertilization resulted in more Cd buildup in the soil than other treatments, but the uptake of Cd by crops was inhibited by the precipitation of Cd with phosphate in the soil. Although soil Cd was slightly increased over the 20 years of intensive crop production, both soil and grain/kernel Cd concentrations were still below the national standards for environmental and food safety.     

上海郊区稻田氮素流失研究

通过测坑和大田小区试验，研究了上海郊区稻田氮素排水流失和渗漏流失的特征、相关因素和流失负荷。结果表明，稻田综合排水TN为6.55mg／L，流失负荷为16．68kg／hm^2，以铵态氮为主，稻田氮素的排水流失负荷为16．68kg／hm^2。稻田渗漏水氮浓度与前茬作物有关，草莓和蔬菜高，麦茬低，TN为5．73mg／L，渗漏负荷为22．92kg／hm^2，其中硝态氮占50％左右。稻田氮素总流失负荷占稻季化肥用量的13．23％。测坑和大田试验都证明，施用有机肥可较多地减少稻田氮素流失量。     

Short-term effects of compost amendment on the fractionation of cadmium in soil and cadmium accumulation in rice plants

Purpose

We used a sequential extraction to investigate the effects of compost amendment on Cd fractionation in soil during different incubation periods in order to assess Cd stabilization in soil over time.

Methods

Pot experiments using rice plants growing on Cd-spiked soils were carried out to evaluate the influence of compost amendment on plant growth and Cd accumulation by rice. Two agricultural soils (Pinchen and Lukang) of Taiwan were used for the experiments. The relationship between the redistribution of Cd fractions and the reduction of plant Cd concentration due to compost amendment was then investigated.

Results and discussion

Compost amendment in Pinchen soil (lower pH) could transform exchangeable Cd into the Fe- and Mn-oxide-bound forms. With increasing incubation time, exchangeable Cd tended to transform into carbonate- and Fe- and Mn-oxide-bound fractions. In Lukang soil (higher pH), carbonate- and Fe- and Mn-oxide-bonded Cd were the main fractions. Exchangeable Cd was low. Compost amendment transformed the carbonate-bound form into the Fe and Mn oxide form. Pot experiments of rice plants showed that compost amendment enhanced plant growth more in Pinchen soil than in Lukang soil. Compost amendment could significantly reduce Cd accumulation in rice roots in both Pinchen and Lukang soils and restrict internal transport of Cd from the roots to the shoots. Because exchangeable Cd can be transformed into the stronger bonded fractions quickly in Pinchen soil, a reduction of Cd accumulation in rice due to compost amendment of Pinchen soil was significant by 45?days of growth. However, carbonate-bonded fractions in Lukang soil may provide a source of available Cd to rice plants, and exchangeable and carbonate-bonded fractions are transformed into the other fractions slowly. Thus, reduction of Cd accumulation by rice due to compost amendment in Lukang soil was significant by 75?days of growth.

Conclusions

The results of the study suggest that the effectiveness of compost amendment used for stabilization of Cd and to decrease the phytoavailability of Cd for rice plants is different in acidic and alkaline soils. In acidic soil, Cd fractionation redistributes quickly after compost amendment and shows a significant reduction of Cd accumulation by the plant within a few weeks. In alkaline soil, due to the strongly bound fractions of Cd being in greater quantity than the weakly bound ones, a longer period (a few months) to redistribute Cd fractions is needed.     

Evaluation of heavy metal contents in co-composts of poultry manure with barley wastes or chestnut burr/leaf litter

The presence of heavy metals in composts is a main cause of adverse effects on animal and human health, transmitted through the food chain from the soil, groundwater and plants. In this study, the contents of Zn, Cd, Pb and Cu present in co-composts of poultry manure (liquid or solid) with a co-composting material (barley wastes or chestnut burr/leaf litter) were assessed. A compost of solid manure was used as control because a compost cannot be obtained from the liquid manure. The original solid poultry manure showed a Zn content of 2134+/-75 mg/kg, exceeding the current legal limit in Spain of 1100 mg/kg. In the solid poultry manure co-compost with chestnut burr/leaf litter and barley wastes, Zn content decreased to 813+/-25 mg/kg and 883+/-37 mg/kg, respectively. The contents in heavy metals (Zn, Cd, Pb and Cu) of the co-composts were under the maximum limit permitted under the Spanish legislation, excepting for the Zn level in liquid poultry manure co-composted with chestnut burr/leaf litter.