Hamaad Raza Ahmad

Contrasting effects of biochar, compost and farm manure on alleviation of nickel toxicity in maize (Zea mays L.) in relation to plant growth, photosynthesis and metal uptake

Nickel (Ni) toxicity in agricultural crops is a widespread problem while little is known about the role of biochar (BC) and other organic amendments like farm manure (FM) from cattle farm and compost (Cmp) on its alleviation. A greenhouse experiment was conducted to evaluate the effects of BC, Cmp and FM on physiological and biochemical characteristics of maize (Zea mays L.) under Ni stress. Maize was grown in Ni spiked soil without and with two rates of the amendments (equivalent to 1% and 2% organic carbon, OC) applied separately to the soil. After harvest, plant height, root length, dry weight, chlorophyll contents, gas exchange characteristics and trace elements in plants were determined. In addition, post-harvest soil characteristics like pHs, ECe and bioavailable Ni were also determined. Compared to the control, all of the amendments increased plant height, root length, shoot and root dry weight with the maximum increase in all parameters by FM (2% OC) treatment. Similarly, total chlorophyll contents and gas exchange characteristics significantly increased with the application of amendments being maximum with FM (2% OC) application. Amendments significantly increased copper, zinc, manganese and iron concentrations and decreased Ni concentrations in the plants. The highest reduction in shoot Ni concentration was recorded with FM (2% OC) followed by BC (2% OC) being 73.2% and 61.1% lower compared to the control, respectively. The maximum increase in soil pH and decrease in AB-DTPA extractable Ni was recorded with BC (2% OC) followed by FM (2% OC). It is concluded that FM (2% OC) was the most effective in reducing Ni toxicity to plants by reducing Ni uptake while BC (2% OC) was the most effective in decreasing bioavailable Ni in the soil through increasing soil pH. However, long-term field studies are needed to evaluate the effects of these amendments in reducing Ni toxicity in plants.

Organic and Inorganic Amendments Affect Soil Concentration and Accumulation of Cadmium and Lead in Wheat in Calcareous Alkaline Soils

Irrigation with untreated effluent in periurban agriculture could result in accumulation and bioconcentrations of cadmium (Cd) and lead (Pb). Different amendments were used to investigate their effect on availability, concentration, and uptake of metals by wheat in texturally different soils. Crop was irrigated with water containing Cd and Pb at 20 mg L−1, thereby adding 260 mg pot−1 of each metal. Amendments included calcium carbonate at 6 or 12%, gypsum at 50 or 100% of the soil gypsum requirement, farm manure at 7.50 or 15.00 g kg−1 soil, and a control. Amendments decreased ammonium bicarbonate diethylenetriaminepentaacetic acid (AB-DTPA)–extractable Cd and Pb concentrations and uptake by wheat. Dry matter, concentration, uptake, and extractability of Cd and Pb were greater in sandy loam soil compared with those in sandy clay loam soil irrespective of amendments. Sequential extraction showed that more metals were extracted from the control in all fractions and that predominantly metals were found in the carbonate fraction.

Phytoremediation: Mechanisms and Adaptations

Metal contamination of soils is ubiquitous around the globe. Metals accumulate in the soils to toxic levels that may lead to accumulation of metals in plants to unacceptable levels. Metal accumulation is a subject of serious concern due to the threat to plant growth, soil quality, animal and human health. Cleaning up of the soils to remove metals is a current necessity, but it is a challenging task. Different technologies being used nowadays are ex situ which ensues in destruction of soil structure thus leaving it non-useable with poor vegetative cover. Growing plants to clean up the soils is a cost-effective and environmentally friendly alternative. Phytoremediation seems attractive due to non-invasive and non-destructive technology which leaves the soil intact and biologically productive. Plants use different adaptive mechanisms to accumulate or exclude metals, thus maintaining their growth. Accumulation and tolerance of metals by the plants is a complex phenomenon. Movement of metals across the root membrane, loading and translocation of metals through the xylem and sequestration and detoxification of metals at cellular and whole plant levels are important mechanisms adopted by accumulator plants. Understanding the mechanism involved in phytoremediation is necessary to effectively use this technique for metal-contaminated soils. This chapter discusses different mechanisms adopted by plants for remediation of metal-contaminated soils.

Spatial, temporal and size distribution of particulate matter and its chemical constituents in Faisalabad, Pakistan

Spatial and temporal variations in aerosol particulate matter (PM) were investigated for distribution over the four seasons of chemical constituents and particle size fractions in Faisalabad, Pakistan from June 2012 to April 2013. At nine sampling sites, four PM mass size fractions (total suspended particulates [TSP], PM 10 , PM 4 and PM 2.5 ) were monitored; simultaneously, TSP mass samples were collected on glass fiber filters using a high volume air sampler. TSP samples (144) were subjected to quantitative chemical analyses for determining trace elements (Pb, Cd, Ni, Zn, Cu, Fe) using atomic absorption spectroscopy, and water-soluble cations (Ca 2+ , Mg 2+ , Na + , K + , NH 4 + ) and anions (Cl – , SO 4 2– and NO 3 – ) by ion chromatography. The highest PM mass concentrations were observed at industrial sites, while they were somewhat lower in major road intersections and lowest in the remote background site. It was also observed that PM mass concentrations were about two to 20 times higher than the standard limits of the World Health Organization and the US Environmental Protection Agency. Coarse particles (TSP, PM 10 and PM 4 ) were found to be highest during the summer, while relatively fine particles (PM 2.5 ) were higher during the winter period. Concentrations of all size fractions were lowest during the monsoon sampling period at all sites. Concentrations of different elements and water-soluble ions also followed the similar temporal pattern as PM mass concentrations. The crustal elements Ca, Fe, Mg and Na were the largest contributors to TSP mass while elements of anthropogenic origin (Pb, Cd, Ni, Cu and Zn) had relatively lower concentrations and also showed a high spatial variation. Among the anions, sulfate (SO 4 2– ) was the predominant species contributing to 50-60% of the total anion concentration. It was found that rainfall, wind speed and relative humidity were the most important meteorological factors affecting PM concentrations. The evaluation of data presented in this paper will serve as a basis for future regional modeling and source apportionment.

Comparison of Low-Molecular-Weight Organic Acids and Ethylenediaminetetraacetic Acid to Enhance Phytoextraction of Heavy Metals by Maize

We compared acetic, ascorbic, and oxalic acids with ethylenediaminetetraacetic acid (EDTA) to enhance phytoextraction of nickel (Ni), manganese (Mn), zinc (Zn), copper (Cu), cadmium (Cd), and lead (Pb) by maize. Except ascorbic acid, acids significantly (P < 0.05) decreased shoot dry weight with maximum (5.60 g pot−1) recorded with ascorbic acid and minimum with oxalic acid (4.06 g pot−1). Maximum ammonium bicarbonate–diethylenetriaminepenta acetic acid (AB-DTPA)–extractable nickel (19.94 mg kg−1) was recorded with EDTA and it was minimum (10.57 mg kg−1) with oxalic acid. The EDTA significantly (P < 0.05) increased AB-DTPA-extractable lead while other acids decreased it. Except acetic acid, other acids significantly (P < 0.05) increased Ni and Zn concentration in shoots with maximum Ni (9.22 mg kg−1) and Zn (37.40 mg kg−1) with EDTA.

Silicon: A Beneficial Nutrient Under Salt Stress, Its Uptake Mechanism and Mode of Action

Food security is a serious issue in this era of rapidly growing population. Food security is threatened due to low crop yields around the world due to different biotic and abiotic stresses. The arable lands are decreasing due to different soil degradation process and thus prospect for increasing crop yields through extending areas under cultivation are not very bright. Hence, to achieve the food security on a sustainable basis, it is necessary to utilize degraded soils productively. Among the degraded soils, Salt-affected soils share the major fraction and their presence is prevalent in all continents. The adoption of different management techniques for productive use of salt-affected soils is thus pre-requisite for enhancing crop yields on such soils. These management strategies include management of irrigation water, reclamation techniques, raising beds, organic matter and salt tolerant crops like kallar grass. In addition to these, better fed plants have good potential to withstand with salinity and other stresses. Exogenous application of nutrients can alleviate the detrimental effects of salts. Silicon (Si) as a beneficial nutrient is known to improve plant growth particularly under abiotic stresses. It is helpful for plants in many ways as it improves plant water status in the context of relative water content and transpiration rate. The role of Si to promote the plant growth under salt-affected soils is reviewed in detail in this chapter.

Sources and Composition of Waste Water: Threats to Plants and Soil Health

Industrialization has caused huge changes in the global budget of critical chemicals at the earth’s surface. Waste water is being added to the soil with or without treatment, causing accumulation of metals, salts, pathogens, toxins etc. in the soil. Accumulation of these substances in soil ultimately affects crop growth and human health. Metals, salts, pathogens are added into soils through various means like pesticides, fertilizer, waste water and municipal waste either remain in the soil by forming insoluble complexes with soil constituents or taken up by plants and/or may pass into drainage water. The waste water contains toxic material likely to affect plants and human health. For Agricultural irrigation may result sail salinity, sodicity and heavy metal accumulation. The untreated waste water coming from various sources contains nutrients and excess of these nutrients resulting eutrophication. However, the waste water might also bring benefits for agricultural crops as it contains organic matter and essential nutrients. The common processes which have been used to remove non-biodegradable pollutants from waste water are sedimentation, flocculation, membrane filtration, photo catalysis and use of different sorbent materials. The present chapter will provide general understanding about the different sources of waste water, its composition and impacts on soil and plant health.

Phosphorus Deficiency in Plants: Responses, Adaptive Mechanisms and Signaling

Phosphorus (P) deficiency is a common nutritional factor limiting agricultural production around the globe. Application of phosphatic fertilizers is generally recommended to cope with P deficiency; however, low use efficiency of available P fertilizers both in calcareous and acid soils limits its viability and also had serious environmental concerns. Higher plants have adapted a number of mechanism to live with low available P in soil such as changes in root morphology and architecture, decreased growth rate, improved P uptake and utilization efficiency, and exudation of organic acids and enzymes to solubilize external inorganic and organic P compounds in the rhizosphere. Plant species and even cultivars widely differ in P efficiency because of differences in one or more of these mechanisms. Exploitation of these genetic variations among crop plants can sustain agricultural production. Understanding the mechanism involved in sensing P deficiency could facilitate selection, breeding, and genetic engineering approaches to improve crop production in P-stressed environments and could reduce dependence on nonrenewable inorganic P resources. In this chapter, we briefly reviewed the responses of P deficiency in higher plants, their adaptive mechanisms, and signaling pathways.

WHEAT ASSIMILATION OF NICKEL AND ZINC ADDED IN IRRIGATION WATER AS AFFECTED BY ORGANIC MATTER

Wastewater irrigation is becoming important around big cities where crops, especially vegetables, are grown. City effluent being a mix of house and factory waste contains organic matter, salts and metals including toxic ones like nickel (Ni), lead (Pb), chromium (Cr), etc., which could be made a part of food chain through phytoassimilation. Hence, a pot culture study was conducted to observe the effect of artificially applied Ni and zinc (Zn) with or without the presence of organic matter (OM) on their uptake by wheat crop in a sandy loam soil. Biomass production was depressed by the application of nickel alone while, Ni and Zn applied in combination produced maximum biomass. Concentrations of both metals were higher in grains than in straw and organic matter application further increased their concentrations in plant parts except for Ni in control. In post-experiment soil, there was less ammonium bicarbonate (AB)- diethylenetriaminepentaacetic acid (DTPA) extractable Ni in organic matter receiving treatments while the Zn showed mixed response with respect to its extractability.

Effects of Rare Earth Oxide Nanoparticles on Plants

Abstract Rare earth oxide nanoparticles (REONPs) have a high privilege in agriculture due to their unique properties as compared to their bulk counterparts. The most important REONPs include scandium, cerium, and other lanthanides, which are frequently used as fertilizer additives in many countries. Several approaches are being adopted for the commercial synthesis of REONPs. The available literature presents contradictory reviews about their beneficial effects on living organisms. Beneficial or harmful effects on plant growth are mainly dependent on the concentration of REONPs and species of plant. Bioavailability and mobility of REONPs in soil is a pH-dependent process and is also affected by their interaction with anionic ligands because of the higher oxidation state of REONPs. Plants can uptake REONPs from the soil and distribute them to aerial parts including edible organs. Accumulation of REONPs within various plant parts exhibits the potential to initiate seed emergence, escalate root and shoot growth, enhance plant growth by increasing the availability of mineral nutrients, stimulate photosynthetic processes, support plants to cope with environmental stresses by acting as a scavenger of free radicles including oxygen species, start oxidase activity, initiate antioxidant systems, and modify the enzyme activation process. Along with all these blessings there are still controversies regarding their effects on plants. This chapter is helpful for answering all ambiguous questions related to the unique characteristics of REONPs, their uptake mechanism, their interaction with soil organic and inorganic components, and their impacts on plant growth. This discussion also elucidates the phytotoxicity of REONPs in plants and their potential to accumulate in plants. This discussion helps to explore new horizons for the beneficial use of REONPs to maximize plant growth and yield on a sustainable basis along with the quality of the produce.