Abdelbasset Lakhdar

Effectiveness of compost use in salt-affected soil

Soil degradation and salinization are two of the utmost threat affecting agricultural areas, derived from the increasing use of low quality water and inappropriate cultural practices. The problem of low productivity of saline soils may be ascribed not only to their salt toxicity or damage caused by excess amounts of soluble salts but also arising from the lack of organic matter and available mineral nutrients especially N, P, and K. Concerns about salinization risk and environmental quality and productivity of agro-ecosystems have emphasized the need to develop management practices that maintain soil resources. Composted municipal solid waste (MSW) was commonly used to enhance soil productivity in the agricultural lands and rebuild fertility. However, their application could be also a promising alternative to alleviate the adverse effects caused by soil salinization. MSW compost, with high organic matter content and low concentrations of inorganic and organic pollutants allow an improvement of physical, chemical and biochemical characteristics and constitute low cost soil recovery.

Accumulation and fractionation of trace metals in a Tunisian calcareous soil amended with farmyard manure and municipal solid waste compost

A field plots experiment was carried out to assess the effects of repeated application of municipal solid waste compost in comparison to farmyard manure on the accumulation and distribution of trace metals, as well as organic carbon and nitrogen in Tunisian calcareous soil. Compared with untreated soil, the application of the two organic amendments significantly increased the organic carbon and nitrogen contents of the soil. Particle-size fractionations showed that carbon and nitrogen were mainly found to occur in the macro-organic matter fraction (80%). The two organic amendments significantly increased organic carbon in the macro-organic and mineral >150 microm fraction and the 150-50 microm fraction, as well as the organic nitrogen in 150-50 microm and macro-organic fraction. Compared with farmyard manure, municipal solid waste compost significantly increased total Cd, Cu, Pb and Zn contents in the topsoil. These trace metals were mainly present in the macro-organic matter fraction. Significant increases of Cu, Zn and Pb were detected in the 150-50 microm, <50 microm and macro-organic fractions after application of municipal solid waste compost. A significant increase of Cd content was only observed in the 150-50 microm fraction. The trace metals also showed different fractionation patterns when the BCR sequential extraction scheme was applied on untreated and compost-treated soil. The residual fraction was found to be the major fraction, especially for Cu, Cr, Ni and Zn. In contrast, Cd was mainly present in the acid-extractable and reducible fraction, whereas Pb was mainly associated with the reducible fraction.

Application of municipal solid waste compost reduces the negative effects of saline water in Hordeum maritimum L.

The efficiency of composted municipal solid wastes (MSW) to reduce the adverse effects of salinity was investigated in Hordeum maritimum under greenhouse conditions. Plants were cultivated in pots filled with soil added with 0 and 40tha(-1) of MSW compost, and irrigated twice a week with tap water at two salinities (0 and 4gl(-1) NaCl). Harvests were achieved at 70 (shoots) and 130 (shoots and roots) days after sowing. At each cutting, dry weight (DW), NPK nutrition, chlorophyll, leaf protein content, Rubisco (ribulose-bisphosphate carboxylase/oxygenase) capacity, and contents of potential toxic elements were determined. Results showed that compost supply increased significantly the biomass production of non salt-treated plants (+80%). This was associated with higher N and P uptake in both shoots (+61% and +80%, respectively) and roots (+48% and +25%, respectively), while lesser impact was observed for K+. In addition, chlorophyll and protein contents as well as Rubisco capacity were significantly improved by the organic amendment. MSW compost mitigated the deleterious effect of salt stress on the plant growth, partly due to improved chlorophyll and protein contents and Rubisco capacity (-15%, -27% and -14%, respectively, in combined treatment, against -45%, -84% and -25%, respectively, in salt-stressed plants without compost addition), which presumably favoured photosynthesis and alleviated salt affect on biomass production by 21%. In addition, plants grown on amended soil showed a general improvement in their heavy metals contents Cu2+, Pb2+, Cd2+, and Zn2+ (in combined treatment: 190%, 53%, 168% and 174% in shoots and 183%, 42%, 42% and 114% in roots, respectively) but remained lower than phytotoxic values. Taken together, these findings suggest that municipal waste compost may be safely applied to salt-affected soils without adverse effects on plant physiology.

THE EFFECT OF COMPOST AND SEWAGE SLUDGE ON SOIL BIOLOGIC ACTIVITIES IN SALT AFFECTED SOIL

Saline soil was amended with 13.3 and 26.6 g kg -1 of Municipal Solid Waste (MSW) compost or sewage sludge, and arylsulphatase (ARY), phosphatase (PHO), dehydrogenase (DEH), β-glucosidase (β-GLU), urease (URE) and catalase (CAT) activities as well as physical-chemical properties were determined after 70 day of incubation under laboratory conditions. MSW compost and sewage sludge significantly improved soil physical-chemical properties, especially carbon and nitrogen contents. Accordingly, overall enzyme activities were substantially promoted in presence of both amendments and the higher increases were measured at 13.3 g kg -1 of MSW compost (increases by 107%, 43%, 20%, 11%, and 148% for, DEH, β-GLU, PHO, URE, and CAT, respectively). Lower beneficial effects occurred at 26.6 g kg -1 of sewage sludge possibly because of the increased salinity or the presence of trace elements by sewage sludge application. As a general response, MSW compost supplied at 13.3 g kg -1 seems

Effect of municipal solid waste compost and sewage sludge use on wheat (Triticum durum): growth, heavy metal accumulation, and antioxidant activity.

BACKGROUND Inappropriate utilisation of biosolids may adversely impact agrosystem productivity. Here, we address the response of wheat (Triticum durum) to different doses (0, 40, 100, 200 and 300 t ha(-1)) of either municipal solid waste (MSW) compost or sewage sludge in a greenhouse pot experiment. Plant growth, heavy metal uptake, and antioxidant activity were considered. RESULTS Biomass production of treated plants was significantly enhanced at 40 t ha(-1) and 100 t ha(-1) of MSW compost (+48% and +78% relative to the control, respectively). At the same doses of sewage sludge, the increase was only 18%. Higher doses of both biosolids restricted significantly the plant growth, in concomitance with the significant accumulation of heavy metals (Ni2+, Pb2+, Cu2+ and Zn2+), especially in leaves. Leaf activities of antioxidant enzymes (ascorbate peroxidase, glutathione reductase, catalase and superoxide dismutase) were unchanged at 40 t ha(-1) MSW compost or sewage sludge, but were significantly stimulated at higher doses (200-300 t ha(-1)), together with higher leaf concentration of reduced glutathione. CONCLUSION This preliminary study suggests that a MSW supply at moderate doses (100 t ha(-1)) could be highly beneficial for wheat productivity.

Differential Responses in Potassium Absorption and Use Efficiencies in the Halophytes Catapodium rigidum and Hordeum maritimum to Various Potassium Concentrations in the Medium

Abstract The changes in biomass production, root length, mineral nutrition, potassium absorption efficiency (KAE), and potassium use efficiency (KUE) of the halophytes Catapodium rigidum and Hordeum maritimum in response to potassium availability were assessed under natural conditions. Plants were cultivated in the greenhouse of the experimental station of the Biotechnology Centre of Borj Cédria (a Mediterranean coastal area) 30 km south-east of Tunis for four months from the autumn to winter of 2007–2008. H. maritimum biomass production was not significantly affected by the K+ concentration, but C. rigidum growth was increased significantly with increasing K+ concentration in the medium. Root/shoot dry weight ratio remained constant in C. rigidum, but decreased significantly at 1000 and 3000 µM K+ in H. maritimum. KAE increased but KUE decreased significantly with increasing K+ concentration in the medium in both species. However, KAE was higher in H. maritimum than in C. rigidum showing a contrasting response to K+ concentration between the two species. Overall, the maintenance of a cationic balance may be explained by cation antagonism. The lower K+ requirement of H. maritimum to express its optimal growth can be attributed to its higher efficiency to acquire and transfer K+ to shoots.

PHYTODESALINATION OF A MODERATELY-SALT-AFFECTED SOIL BY SULLA CARNOSA

The aim of this investigation was to evaluate the ability of the indifferent halophyte Sulla carnosa Desf. to desalinize a moderately-salt-affected soil. Seeds were sown on a fertile soil added or not with 1.5 g NaCl. kg−1. Analogous treatments without plantation (control and salinized) were also used. Plant culture was performed under greenhouse conditions in non-perforated pots containing 10 kg soil each and irrigated with non-saline tap water. After 80 days of treatment, shoots were harvested. Soil samples were also collected after division of soil column in each pot into two horizons. Our results showed that salt addition increased electrical conductivity of saturation paste extract (ECe) from 3.3 to 8.4 dS. m−1 and soluble sodium concentration from 0.32 to 1.15 g. kg−1 soil in the upper horizon. In the lower horizon however, Na+ concentration was quasi-constant and then ECe was less increased. Plant culture inversed this pattern of sodium accumulation and salinity. Its productivity and phytodesalination capacity in 80 days were 5.0 t DW. ha−1 and 0.3 t Na+. ha−1 (24% of the added quantity), respectively. Interestingly, sodium dilution within biomass (41.5–45.6 mg. g−1 DW) and the non-altered nutrition make this plant suitable for forage as second use after phytodesalination.

Municipal solid waste compost application improves productivity, polyphenol content, and antioxidant capacity of Mesembryanthemum edule

Organic wastes were successfully used as soil amendment to improve agrosystems productivity. Yet, the effectiveness of this practice to enhance plant antioxidant capacities has received little attention. Here, we assess the effect of municipal solid waste (MSW) compost (at 40 t ha(-1)) on growth, polyphenol contents and antioxidant activities of Mesembryanthemum edule. MSW compost application significantly increased the soil contents of carbon, nitrogen, calcium, phosphorus and potassium. This was associated with higher nutrient (N, P, and K) uptake, which likely led to the significant improvement of the plant biomass and relative growth rate (RGR) (+93% on average) as compared to the control. In the same way, the fertilizing effect of the added organic matter significantly enhanced the antioxidant potential M. edule, assessed by radical scavenging activity, iron reducing power and β-carotene bleaching capacity. This was associated with significantly higher antioxidant contents, mainly total phenols and flavonoids. Heavy metal (Pb, Cd, Cu, and Zn) concentrations were slightly increased upon compost application, but remained lower than phytotoxic values. Overall, our results point out that short-term MSW compost application at 40 t ha(-1) is efficient in enhancing the productivity together with the antioxidant potentiality of M. edule without any adverse environmental impact.

Effect of Municipal Solid Waste Compost and Farmyard Manure Application on Heavy‐Metal Uptake in Wheat

The risks related to municipal solid waste compost application in comparison to farmyard manure and mineral fertilizers on durum wheat were investigated on a short‐term experiment. Compost was applied at 40 t ha−1 and 80 t ha−1 with or without chemical fertilizers. Analogously, farmyard manure was applied at 40 t ha−1. Both compost and farmyard manure improved plant growth and nutrient uptake. However, compost amendment showed more effectiveness, especially at 80 t ha−1. Alternatively, this dose of compost involved an increase of plant copper, cadmium, and zinc concentrations in plant tissues. Metal accumulation did not thwart the enhancement of wheat yield. Furthermore, grain translocation factor reached 1 only in the case of copper; however, it showed a significant decrease following compost application (ranged between 0.57 and 0.69). Bioconcentration factor showed a significant decrease with municipal solid waste compost supply, constituting an internal detoxification mechanism.

Assessing solid waste compost application as a practical approach for salt-affected soil reclamation

Abstract A short-term pot experiment was made to evaluate the effectiveness of municipal solid waste compost amendment on salt-affected soil. Hordeum maritimum plants were cultivated in pots filled with a clay-loam soil containing 0 or 40 t ha−1 of compost and irrigated with tap water at 0 or 4 g l−1 NaCl. Soil properties and heavy metal (Zn2 +, Pb2 +, Cd2 +) accumulation were investigated. Municipal solid waste compost application significantly increased the soil contents of carbon, nitrogen and potassium under both non-saline and saline conditions. Soil heavy metal concentrations increased substantially too, but the recorded values were below the toxicity limits. Interestingly, plants subjected to the salt–compost interaction were more vigorous, compared with those grown on non-amended soil. Altogether, our data indicate that short-term utilization of municipal solid waste compost at 40 t ha−1 may be of potential interest in the perspective of the rehabilitation of salt-affected soils. Yet, it must be stressed that the present findings are preliminary and need to be further evaluated under field conditions before practical recommendations can be inferred.