Enhanced uptake of soil Pb and Zn by Indian mustard and winter wheat following combined soil application of elemental sulphur and EDTA

Enhancement of Pb and Zn uptake by Indian mustard (Brassica juncea (L.) Czern.) and winter wheat (Triticum aestivumL.) grown for 50 days in pots of contaminated soil was studied with application of elemental sulphur (S) and EDTA. Sulphur was added to the soil at 5 rates (0–160 mmol kg^?1) before planting, and EDTA was added in solution at 4 rates (0–8 mmol kg^?1) after 40 days of plant growth. Additional pots were established with the same rates of S and EDTA but without plants to monitor soil pH and CaCl₂-extractable heavy metals. The highest application rate of S acidified the soil from pH 7.1 to 6.0. Soil extractable Pb and Zn and shoot uptake of Pb and Zn increased as soil pH decreased. Both S and EDTA increased soil extractable Pb and Zn and shoot Pb and Zn uptake. EDTA was more effective than S in increasing soil extractable Pb and Zn, and the two amendments combined had a synergistic effect, raising extractable Pb to ¿1000 and Zn to ¿6 times their concentrations in unamended control soil. Wheat had higher shoot yields than Indian mustard and increasing application rates of both S and EDTA reduced the shoot dry matter yields of both plant species to as low as about half those of unamended controls. However, Indian mustard hyperaccumulated Pb in all EDTA treatments tested except the treatment with no S applied, and the maximum shoot Pb concentration was 7100 mg kg^?1 under the highest application rates of S and EDTA combined. Wheat showed similar trends, but hyperaccumulation (1095 mg kg^?1) occurred only at the highest rates of S and EDTA combined. Similar trends in shoot Zn were found, but with lower concentrations than Pb and far below hyperaccumulation, with maxima of 777 and 480 mg kg^?1 in Indian mustard and wheat. Despite their lower yields, Indian mustard shoots extracted more Pb and Zn from the soil (up to 4.1 and 0.45 mg pot^?1) than did winter wheat (up to 0.72 and 0.28 mg pot^?1), indicating that the effects of S and EDTA on shoot metal concentration were more important than yield effects in determining rates of metal removal over the growth period of 50 days. Phytoextraction of Pb from this highly contaminated soil would require the growth of Indian mustard for nearly 100 years and is therefore impractical.     

Effect of sodium selenate on photosynthetic efficiency,antioxidative defence system and micronutrients in maize (<Emphasis Type="Italic">Zea mays</Emphasis>)

Oxidative stress or formation of faulty proteins due to non-specific replacement of sulphur by selenium(Se)/mineral imbalance can be one of the reasons for Se phytotoxicity. Present investigation reports the effect of Se on photosynthetic efficiency, anti-oxidative status and micronutrients in maize. Selenate-Se application (1–32 mg kg^?1 soil) showed significant growth reduction after 30 days of sowing and all the plants died with concentration higher than 4 mg kg^?1 soil. Lower Se doses increased dry matter, chlorophyll, proline and activities of defence enzymes viz. peroxidase, catalase and superoxide dismutase and decreased malondialdehyde, glutathione and glutathione reductase activity as compared to control. All the parameters showed the reverse trend with Se treatment of 4 mg kg^?1 soil. Concentration of nutrients (K, P, S, Mn, Mg and Ca) in leaves decreased with application of increasing Se doses. Shoot and root weight decreased (8.5–31.9% and 12–24%, respectively) in response to varying Se doses and highest Se accumulation in these tissues was observed with Se @ 4 mg kg^?1 soil. The phyto-toxic effects of higher Se doses may be due to its prooxidant effects and disturbances in nutrients level.     

The effect of soil compaction on growth and P uptake by Trifolium subterraneum: interactions with mycorrhizal colonisation

The effects of vesicular-arbuscular mycorrhizal (VAM) colonisation on phosphorus (P) uptake and growth of clover (Trifolium subterraneum L.) in response to soil compaction were studied in three pot experiments. P uptake and growth of the plants decreased as the bulk density of the soil increased from 1.0 to 1.6 Mg m^-3. The strongest effects of soil compaction on P uptake and plant growth were observed at the highest P application (60 mg kg^-1 soil). The main observation of this study was that at low P application (15 mg kg^-1 soil), P uptake and shoot dry weight of the plants colonised by Glomus intraradices were greater than those of non-mycorrhizal plants at similar levels of compaction of the soil. However, the mycorrhizal growth response decreased proportionately as soil compaction was increased. Decreased total P uptake and shoot dry weight of mycorrhizal clover in compacted soil were attributed to the reduction in the root length. Soil compaction had no significant effect on the percentage of root length colonised. However, total root length colonised was lower (6.6 m pot^-1) in highly compacted soil than in slightly compacted soil (27.8 m pot^-1). The oxygen content of the soil atmosphere measured shortly before the plants were harvested varied from 0.18 m³m^-3 in slightly compacted soil (1.0 Mg m^-3) to 0.10 m³m^-3 in highly compacted soil (1.6 Mg m^-3).     

Interactive effects of molybdenum and phosphorus fertilizers on photosynthetic characteristics of seedlings and grain yield of Brassica napus

A pot experiment with acid yellow–brown soil was conducted to investigate the interactive effects of molybdenum (Mo) and phosphorus (P) fertilizers on the photosynthetic characteristics of seedlings and grain yield of Brassica napus which is sensitive to soil P and Mo deficiency. Both Mo and P fertilizers were applied at three levels (0 mg Mo kg^?1, 0.15 mg Mo kg^?1, 0.30 mg Mo kg^?1 soil; 0 mg P kg^?1, 80 mg P kg^?1, 160 mg P kg^?1 soil). The results showed that P fertilizer application increased grain yield, soluble sugar concentrations of seedling leaves, DM and P accumulation of seedling shoots of Brassica napus in the absence or presence of Mo fertilizer. In contrast, Mo fertilizer increased these parameters only in the presence of P fertilizer. Mo accumulation in shoots, chlorophyll concentrations and net photosynthesis rate (P _n) of seedling leaves were increased by both Mo and P fertilizers, particularly with the combination of the two fertilizers. The results also showed that the Mo and P fertilizers increased photosynthetic rate through two different mechanisms, with Mo increasing photosynthetic activity of mesophyll cells, and P increasing stomatal conductance. The results demonstrate that there was a synergetic effect on photosynthesis and grain yield between Mo and P fertilizers and it is conducive for Brassica napus growth to co-apply the two fertilizers.     

Basal and Foliar Treatment using an Organic Fertilizer Amendment Lowers Cadmium Availability in Soil and Cadmium Uptake by Rice on Field Micro-Plot Experiment Planted in Contaminated Acidic Paddy Soil

In the present study, field micro-plot experiments were conducted to investigate the basal and foliar application of a tested organic fertilizer amendment (OFA) for decreasing the risk of Cd accumulating in rice. The results showed that applications of OFA significantly increased rice yields in Cd-polluted soil and reduced the level of Cd in rice plants, especially in rice grain. In addition, three application methods of OFA were investigated (single basal application (B1, B2, and B3), combined basal application (+LM, +D, and +Z), and foliar application (F1, F2)). Treat B, F, +LM, +D were all higher than control on rice yield with 25.03, 28.05, 30.61, 22.50 g pot^?1 on average, respectively. Among which, rice cadmium depress to 0.33 mg kg^?1 in foliar application is considered to be a more efficient and economical method of heavy metal remediation. The mechanism of foliar application to alleviate the accumulation of Cd in brown rice may be related to the probable Cd sequestration in the leaves and straws. And the doses of the foliar application were 2.25–3.75 kg hm^?2, approximately 1.0–2.5% of the basal application amount yet with more effect (0.10 mg kg^?1 more than single basal; 0.23 mg kg^?1 more than combined basal) on Cd reduction.     

Organic fertilizer applications influence on the shoot and root biomass production and plant nutrient of Calopogonium mucunoides from crude oil-contaminated soils

The impact of crude oil-contaminated soil on the shoot and root biomass yield and nutrients uptake of Calopogonium mucunoides Desv. using two types of composted manure (COM) as soil amendments were investigated. This was with a view to assessing the growth response of the test plant under different levels of crude oil soil contamination. Five levels [0, 2.5, 5, 10, and 20% (v/v)] of crude oil, each was replicated thrice to contaminate 3 kg of soil when 12 g pot^?1 COM; 12 g pot^?1 neem-fortified composted manure (NCM) and control, soil without manure application (C) were imposed as manure treatments. The mean fresh shoot biomass yield at zero crude oil soil contamination and with COM application was 2.67 g pot^?1. This value was significantly (p < 0.05) higher than 2.05 g pot^?1 for NCM and 1.67 g pot^?1 for the control. Also, the mean fresh root yield at zero crude oil soil contamination with COM application was 4.02 g pot^?1. This value was significantly (p < 0.05) higher than 2.41 g pot^?1 for NCM and 1.71 g pot^?1 for the control. The dry shoot and root biomass yield followed similar pattern. The shoot and root yield of C. mucunoides significantly (p < 0.05) reduced with increase in crude oil soil contamination. The nutrients uptake of C. mucunoides, particularly N, P, Ca, Mg, and Fe, were enhanced with COM fertilization having higher available P, K, and Na values; and by implication, suggesting the importance of adequately formulated composted manure usage in the rehabilitation studies of crude oil-contaminated soil.     

Effects of biochar and nitrogen addition on nutrient and Cd uptake of Cichorium intybus grown in acidic soil

Biochar is an organic amendment used for soil remediation, there are only a few studies documenting the effects of nitrogen on the role of biochar in contaminated soils. A pot experiment was conducted to investigate the impacts of biochar (0%, 1%, and 2.5%, w/w) and nitrogen (0, 100, and 200 mg N kg^?1) on plant growth, nutrient and cadmium (Cd) uptake of Cichorium intybus. N, P, Ca, Mg, and Cd concentrations increased with N level in 0% and 1% biochar treatments. In plants treated with 2.5% biochar, 200 mg N kg^?1 addition caused significant reductions of N, P, Ca, Mg, and Cd concentrations in comparison to 100 mg N kg^?1 treatments. Nitrogen promoted shoot biomass at all biochar treatments, while biochar had no effect on shoot biomass in 0 and 200 mg N kg^?1 addition treatments. Nitrogen also significantly increased N, P, K, Ca, Mg, and Cd contents in the 0% and 1.5% biochar addition treatments. Although soil DTPA-extractable Cd concentration showed the lowest values in 1% biochar in combination with 100 and 200 mg N kg^?1 addition treatments, lowest shoot Cd concentration, and relatively high shoot biomass occurred in the 2.5% biochar + 200 mg N kg^?1 treatment. Based on these results, biochar application at its highest rate (2.5%) in combination with high N supply (200 mg N kg^?1) contributed to both crop yield and agricultural product safety. N input alone might increase the risk of human health, and the optimum N dose should be determined during phytostabilization process.     

Enhanced phytoremediation of cadmium and/or benzo(a)pyrene contaminated soil by hyperaccumlator Solanum nigrum L.

The role of same amendment on phytoremediating different level contaminated soils is seldom known. Soil pot culture experiment was used to compare the strengthening roles of cysteine (CY), EDTA, salicylic acid (Sa), and Tween 80 (TW) on hyperaccumulator Solanum nigrum L. phytoremediating higher level of single cadmium (Cd) or Benzo(a)pyrene (BAP) and their co-contaminated soils. Results showed that the Cd capacities (ug pot^?1) in shoots of S. nigrum in the combined treatment T_{0.1EDTA+0.9CY} were the highest for the 5 and 15 mg kg^?1 Cd contaminated soils. When S. nigrum remediating co-contaminated soils with higher levels of Cd and BAP, that is, 5 mg kg^?1 Cd + 1 mg kg^?1 BAP and 15 mg kg^?1 Cd + 2 mg kg^?1 BAP, the treatment T_{0.9CY+0.9Sa+0.3TW} showed the best enhancing remediation role. This results were different with co-contaminated soil with 0.771 mg kg^?1 Cd + 0.024 mg kg^?1 BAP. These results may tell us that the combine used of CY, SA, and TW were more useful for the contaminated soils with higher level of Cd and/or BAP. In the combined treatments of Sa+TW, CY was better than EDTA.     

LEAD TOLERANCE AND ACCUMULATION IN PTERIS VITTATA AND PITYROGRAMMA CALOMELANOS,AND THEIR POTENTIAL FOR PHYTOREMEDIATION OF LEAD-CONTAMINATED SOIL

A field survey was conducted to search for Pb accumulation in fern species at Bo Ngam Pb mine, Thailand. Eleven fern species including Pteris vittata accumulated Pb in the range of 23.3–295.6 mg kg^?1 in the aboveground parts. Hydroponic, pot, and field trial experiments were carried out to investigate Pb-accumulation ability in ferns; including P. vittata and the ornamental species, Pityrogramma calomelanos, Nephrolepis exaltata cv. Gracillimum, and N. exaltata cv. Smirha. In hydroponic experiment, Pi. calomelanos accumulated the highest concentration of Pb (root 14161.1 mg kg^?1, frond 402.7 mg kg^?1). The pot study showed that P. vittata, Pi. calomelanos, and N. exaltata cv. Gracillimum grew well when grown in soil Pb at 92900 mg kg^?1. N. exaltata cv. Gracillimum accumulated the highest Pb concentration in the frond (5074 mg kg^?1) and P. vittata accumulated the highest Pb concentration in the root (16257.5 mg kg^?1). All fern species exhibited TF values less than 1 in both hydroponic and pot experiments. When P. vittata and Pi. calomelanos were grown at mine soils for 6 months, P. vittata tolerated higher soil Pb (94584–101405 mg kg^?1) and accumulated more Pb in frond (4829.6 mg kg^?1) and showed TF > 1 after 2 months of growth. These results indicated that P. vittata can be potentially useful for phytoremediation of Pb-contaminated soil.     

Contrasting Effects of Farmyard Manure (FYM) and Compost for Remediation of Metal Contaminated Soil

We investigated effect of farm yard manure (FYM) and compost applied to metal contaminated soil at rate of 1% (FYM-1, compost-1), 2% (FYM-2, compost-2), and 3% (FYM-3, compost-3). FYM significantly (P < 0.001) increased dry weights of shoots and roots while compost increased root dry weight compared to control. Amendments significantly increased nickel (Ni) in shoots and roots of maize except compost applied at 1%. FYM-3 and -1 caused maximum Ni in shoots (11.42 mg kg^?1) and roots (80.92 mg kg^?1), respectively while compost-2 caused maximum Ni (14.08 mg kg^?1) and (163.87 mg kg^?1) in shoots and roots, respectively. Plants grown in pots amended with FYM-2 and compost-1 contained minimum Cu (30.12 and 30.11 mg kg^?1) in shoots, respectively. FYM-2 and compost-2 caused minimum zinc (Zn) (59.08 and 66.0 mg kg^?1) in maize shoots, respectively. FYM-2 caused minimum Mn in maize shoots while compost increased Mn in shoots and roots compared to control. FYM and compost increased the ammonium bicarbonate diethylene triamine penta acetic acid (AB-DTPA) extractable Ni and Mn in the soil and decreased Cu and Zn. Lower remediation factors for all metals with compost indicated that compost was effective to stabilize the metals in soil compared to FYM.     

Judicious use of kinetin to improve growth and yield of rice in nickel contaminated soil

The present study was conducted to evaluate the effect of kinetin on growth and yield of rice in the presence and absence of nickel contamination. Rice seedlings were dipped in kinetin solution (10^?3, 10^?4 and 10 M^?5) for 2 hours and transplanted in pots having soil contaminated with nickel sulfate @ 130 mg kg^?1. Experiment was laid out according to completely randomized design with four replications. Results revealed that kinetin significantly improved growth and yield of rice grown in nickel contamination. Kinetin @ 10^?4 M showed maximum improvement in plant height, paddy yield, 1000 grain weight, number of tillers and panicles up to 9.76, 15.72, 11.77, 11.87, and 10.90%, respectively, as compared to plants grown in contaminated soil without kinetin. Kinetin also improved the uptake of nutrients (NPK) in straw and grain of plants grown in Ni contaminated soil. Plants treated with kinetin had more concentration of Ni in shoot but less in grain compared to plants grown in Ni contaminated soil without application of kinetin. The application of kinetin can reduce stress effect on plants through improvement in the biomass of plant. This strategy could be used to increase the phytoextraction of Ni from the contaminated soil.     

Alley cropping with Senna siamea in South-western Nigeria: I. Recovery of 15N labeled urea by the alley cropping system

Improved cropping systems with in-situ production of organic matter require the input of additional inorganic N to maintain crop production in a sustainable way. For proper management of this fertilizer-N, it is necessary to quantify how the applied fertilizer N is used by the various components of the system and by the system as a whole. The fate of a single application of ¹⁵N labeled urea-N through the different components (crop, hedgerow, surface litter, soil profile up to 150 cm) of a Senna siamea alley cropping system, intercropped with maize in the first and cowpea in the second season, was followed for a period of 1.5 years (1994–1995), equivalent to 2 maize and 1 cowpea crop. Special attention was given to the role of the particulate organic matter (POM) in the cycling of urea-N through the soil organic matter (SOM). The maize crop recovered 26.5 and 1.7% of the applied urea-N at harvest in 1994 and 1995, respectively. The cowpea pods recovered only 0.7% of the applied urea-N at harvest. The highest proportion of applied urea-N recovered by the hedgerow occurred at 38 days after 1994 maize planting (DAP) (3.8%), while at later dates, recoveries of applied urea-N were always below 1%. This indicates that the Senna hedge is not a strong competitor for the applied urea-N during crop growth, i.e. while the Senna canopy is pruned at regular intervals. At 21 DAP, 12.7% of the applied urea-N was recovered in the surface litter and this value dropped significantly to 1.6% at 107 DAP and remained below 1% up to 480 DAP. The top 10 cm of soil contained 21% of the applied urea-N at 21 DAP and this value dropped to 9% at 480 DAP. Significantly more urea-N was recovered in the top 10 cm of soil than in the deeper soil layers at all sampling times. At 21 DAP, 11% of the applied urea-N was recovered in the 120–150 cm layer. This fast movement of urea-derived N to deep soil layers must have happened by preferential flow in macropores as the rainfall between urea application and the first sampling (74.2 mm) was not high enough to explain downward movement of N with the mobile water. Significant linear relationships between the proportion of urea-N in the different soil layers (excluding 0–10 cm) and the anion exchange capacity (AEC) and silt+clay content of the respective layers were found at 67, 107, 347 and 480 DAP. The total N content of the POM fraction increased significantly between 0 and 101 DAP from 127 to 171 mg N kg^–1 and decreased to 92 mg N kg^–1 at 480 DAP. The highest recovery of applied urea-N in the POM pool was measured at 101 DAP (3.6%) and this value decreased to 1.8% at 480 DAP. The total recovery of applied urea-N was 81% at 21 DAP, and decreased to values varying between 53 and 60% up from 38 to 347 DAP. At 480 DAP, the recovery decreased further to 47%. The fast movement of a substantial amount of urea-N may be responsible for this incomplete recovery, already at 21 DAP. Although the soil N status in the fertilized alley cropping system appears to be favourable for plant growth, this may be short-lived in the absence of further urea additions, as the soil-derived maize uptake in 1995 was already significantly lower than in 1994, and as the labile POM pool decreased significantly between the maize harvest in 1994 and 1995.     

Interaction between root growth allocation and mycorrhizal fungi in soil with patchy P distribution

Aims and Background

Many plants preferentially grow roots into P-enriched soil patches, but little is known about how the presence of arbuscular mycorrhizal fungi (AMF) affects this response.

Methods

Lotus japonicus (L.) was grown in a low-P soil with (a) no additional P, (b) homogeneous P (28 mg pot^?1), (c) low heterogeneous P (9.3 mg pot^?1), and (d) high heterogeneous P (28 mg pot^?1). Each P treatment was combined with one of three mycorrhiza treatments: no mycorrhizae, Glomus intraradices, indigenous AMF. Real-time PCR was used to assess the abundance of G. intraradices and the indigeneous AMF G. mosseae and G. claroideum.

Results

Mycorrhization and P fertilization strongly increased plant growth. Homogeneous P supply enhanced growth in both mycorrhizal treatments, while heterogeneous P fertilization increased biomass production only in treatments with indigenous AMF inoculation. Preferential root allocation into P-enriched soil was significant only in absence of AMF. The abundance of AMF species was similar in P-enriched and unfertilized soil patches.

Conclusion

Mycorrhization may completely override preferential root growth responses of plants to P- patchiness in soil. The advantage of this effect for the plants is to give roots more freedom to forage for other resources in demand for growth and to adapt to variable soil conditions.     

Impact of long-term additions of chemical fertilizers and farm yard manure on carbon and nitrogen sequestration under rice-cowpea cropping system in semi-arid tropics

Restoration of soil organic carbon (SOC) in arable lands represents potential sink for atmospheric CO₂. The strategies for restoration of SOC include the appropriate land use management, cropping sequence, fertilizer and organic manures application. To achieve this goal, the dynamics of SOC and nitrogen (N) in soils needs to be better understood for which the long-term experiments are an important tool. A study was thus conducted to determine SOC and nitrogen dynamics in a long-term experiment in relation to inorganic, integrated and organic fertilizer application in rice-cowpea system on a sandy loam soil (Typic Rhodualf). The fertilizer treatments during rice included (i) 100% N (@ 100 kg N ha^?1), (ii) 100% NP (100 kg N and 50 kg P₂O₅ ha^?1), (iii) 100% NPK (100 kg N, 50 kg P₂O₅ and 50 kg K₂O ha^?1) as inorganic fertilizers, (iv) 50% NPK + 50% farm yard manure (FYM) (@ 5 t ha^?1) and (v) FYM alone @ 10 t ha^?1 compared with (vi) control treatment i.e. without any fertilization. The N alone or N and P did not have any significant effect on soil carbon and nitrogen. The light fraction carbon was 53% higher in NPK + FYM plots and 56% higher in FYM plots than in control plots, in comparison to 30% increase with inorganic fertilizers alone. The microbial biomass carbon and water-soluble carbon were relatively higher both in FYM or NPK + FYM plots. The clay fraction had highest concentration of C and N followed by silt, fine sand and coarse sand fractions in both surface (0–15 cm) and subsurface soil layers (15–30 cm). The C:N ratio was lowest in the clay fraction and increased with increase in particle size. The C and N enrichment ratio was highest for the clay fraction followed by silt and both the sand fractions. Relative decrease in enrichment ratio of clay in treatments receiving NPK and or FYM indicates comparatively greater accumulation of C and N in soil fractions other than clay.     

Soil solution dynamics and plant uptake of cadmium and zinc by durum wheat following phosphate fertilization

A growth chamber study was conducted to evaluate the effect of application of phosphate fertilizer on soil solution dynamics of cadmium (Cd) and Cd accumulation in durum wheat (Triticum turgidum L. var. durum). Treatments consisted of three phosphate fertilizer sources containing 3.4, 75.2, and 232 mg Cd kg^?1 applied at three rates (20, 40 and 80 mg P kg^?1) plus a no fertilization control. An unplanted treatment at 40 mg P kg^?1 was included to separate the effects on soil solution Cd dynamics of the crop from that of the fertilizer. Soil solution samples were obtained using soil moisture samplers every 10 days after germination. The experimental results indicated that plant biomass significantly increased with P application rates and decreased with increased Cd concentration in the phosphate fertilizers. Total cadmium concentration in soil solution was not consistently affected by phosphate fertilization rate and fertilizer sources, and therefore Cd concentration in the fertilizer. Application of phosphate fertilizer, however, increased the concentration and accumulation of Cd and shoot Cd/Zn ratio, and decreased shoot Zn concentration in durum wheat. Phosphate sources had a marginally significant effect (P?=?0.05) on shoot Cd concentration and did not affect Cd accumulation in durum wheat. Concentration of Cd in soil solution was unrelated to Cd concentration in durum wheat. These results suggest that the immediate increase in Cd concentration and Cd accumulation in durum wheat with phosphate application is due more to competition between Zn and Cd for absorption into plants, enhanced root to shoot translocation and enhanced root development, than to a direct addition effect from Cd contained in phosphate fertilizer. In the short term, application of phosphate fertilizers can increase Cd concentration in the crops, regardless of the Cd concentration of the fertilizer. An optimal P fertilization, possibly in combination with Zn application, may offer an important strategy for decreasing Cd concentration and accumulation in crops.     

LEAD PHYTOEXTRACTION BY WHEAT IN RESPONSE TO THE EDTA APPLICATION METHOD

Lead solubilization in soil and accumulation by spring wheat (Triticum aestivum L.) was studied in response to the ethylenediaminetetraacetic acid (EDTA) application method. In this study, 4 mmol EDTA kg^?1 was applied using two application methods (a single dose and split doses) either alone or in combination with elemental sulfur. Results indicate that the application of EDTA in four equal splits at 1 mmol kg^?1 during the growth period resulted in significantly higher shoot dry matter than its application at 4 mmol kg^?1 at once 10 d before harvesting the wheat crop at the bolting stage. EDTA applied in split doses resulted in less lead (Pb) solubilization as compared with the single-dose application. The split application also significantly increased the shoot Pb concentration and Pb accumulation by wheat shoots as compared with the single-dose application. Despite its lesser effect on Pb solubilization, the EDTA application in split doses substantially increased Pb accumulation; thus, it is expected to minimize the risk of groundwater contamination.     

Sodium-potassium interaction on growth,yield and quality of tomato in ultisol

Abstract

The interaction of sodium (Na) and potassium (K) on growth, yield, nutrients and citric acid composition of fruit of tomato (Lycopersicon lycopersicum [L.] Karst) was investigated. Six rates of Na at 0, 2, 4, 8, 16 and 32 mgkg^?1 soil and four rates of K at 0, 32, 64 and 128 mgkg^?1 soil, applied as NaCl and KCl, respectively, were arranged in a randomized complete block design and replicated three times. Plant growth rate, number of flowers and fruit yields, nutrient composition and citric acid content of fruit juice were determined. The application of 2–4 mg Na kg^?1 soil with 32–64 mg K kg^?1 soil increased fruit yield by about 100%. Fruit yield correlated positively with the number of leaves (0.65***), number of flowers (0.57**) and shoot-N (0.40*). Sodium applied at Na:K ratio of 1:8 to 1:32 increased the growth and yield of the tomato plant.     

Trace element transfer from two contaminated soil series to Medicago sativa and one of its herbivores,Spodoptera exigua

Alfalfa was cultivated in two potted soil series obtained from two sandy soils contaminated by Cu (SM) and metal(loids)/PAH (CD). Shoot production was monitored for 8 weeks. Then, larvae of Spodoptera exigua were reared on alfalfa of both soil series for eight days. A biotest (using Phaseolus vulgaris) was used to assess the soil phytotoxicity. Increasing soil contamination reduced P. vulgaris growth, but alfalfa growth was only reduced on the SM soil series. Exposure to the SM soil was mirrored by shoot Cu and Cr concentrations of alfalfa (respectively, in mg kg ^?1 DW, Cu and Cr ranged from 11.9 and 0.4 in the CTRL soil to 98.5 and 1.2 in the SM one). Exposure to the CD soil series was mirrored by shoot Zn concentrations (i.e., 48–91.6 mg kg^?1 DW). Internal metal(loid) concentrations of S. exigua remained generally steady across both soil series (respectively Cd 0.05–0.16, Cr 0.5–3.3, Cu 5.8–98.5, Ni 0.6–1.6, Pb 0.4–1.3, and Zn 57–337 mg kg^?1 DW), and most of the associated transfer factors were lower than 1. Here, due to the excluder phenotype of alfalfa across our TE contamination gradients, S. exigua could cope with high total metal(loid) concentration in both contaminated soils.     

Feasibility of Typha Latifolia for High Salinity Effluent Treatment in Constructed Wetlands for Integration in Resource Management Systems

High salinity wastewaters have limited treatment options due to the occurrence of salt inhibition in conventional biological treatments. Using recirculating marine aquaculture effluents as a case study, this work explored the use of Constructed Wetlands as a treatment option for nutrient and salt loads reduction. Three different substrates were tested for nutrient adsorption, of which expanded clay performed better. This substrate adsorbed 0.31 mg kg^?1 of NH₄ ⁺?N and 5.60 mg kg^?1 of PO₄ ^3??P and 6.9 mg kg^?1 dissolved salts after 7 days of contact. Microcosms with Typha latifolia planted in expanded clay and irrigated with aquaculture wastewater (salinity 2.4%, 7 days hydraulic retention time, for 4 weeks), were able to remove 94% NH₄ ⁺?N (inlet 0.25 ± 0.13 mg L^?1), 78% NO₂ ^??N (inlet 0.78 ± 0.62 mg L^?1), 46% NO₃ ^??N (inlet 18.83 ± 8.93 mg L^?1) whereas PO₄ ^3??P was not detected (inlet 1.41 ± 0.21 mg L^?1). Maximum salinity reductions of 52% were observed. Despite some growth inhibition, plants remained viable, with 94% survival rate. Daily treatment dynamics studies revealed rapid PO₄ ^3??P adsorption, unbalancing the N:P ratio and possibly affecting plant development. An integrated treatment approach, coupled with biomass valorization, is suggested to provide optimal resource management possibilities.     

Organic Amendments to Enhance Atrazine and Metamitron Degradation in Two Contaminated Soils with Contrasting Textures

Among all types of xenobiotics, pesticides such as herbicides play a significant role in soil and water pollution due to their wide usage all over the world. This study addresses the ability of organic amendments to enhance atrazine and metamitron degradation in two herbicide-contaminated soils with contrasting textures under laboratory conditions. Soil samples were collected from surface soils with textures of sandy loam and silty clay, from northeastern Iran. Initial concentration of herbicides was 50 mg · kg^{? 1} soil. Contaminated soil samples were treated with manure, compost and vermicompost at rates of 0, 0.5, and 2% (w/w). Residual concentrations of atrazine and metamitron were determined by HPLC at the end of incubation periods of 20, 40, and 60 days. Residual concentrations of atrazine were 46.5, 38.9, and 36.2 mg · kg^{? 1} after 20, 40, and 60 days incubation, respectively. Residual metamitron concentrations were clearly lower than atrazine. After 20, 40, and 60 days, concentrations of metamitron were 2.9, 1.0, and 0.6 mg · kg^{? 1}, respectively. Organic amendments at the rates of 0.5 and 2% showed similar effects on the enhancement of herbicide degradation in soils. However, no statistically significant effect was observed among types of organic amendments (α = 0.05). Degradation was affected by soil textures. Residual concentrations of herbicides were higher in sandy loam than in silty clay soil.