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Nickel (Ni) contamination in soil is a widespread problem in this era of industrial development. Plant cultivars respond differentially to Ni contamination in soil. In the present study, we have investigated the effect of different Ni levels to the growth and mineral status of two wheat cultivars (Sehar-2006 and LU-26). Five different levels of Ni as NiSO4 · 4 H2O (0, 30, 45, 60, and 75 mg kg−1) were applied to soil in the pots. LU-26 performed better compared to Sehar-2006 in terms of dry weight production and physiological parameters. LU-26 contained higher Ni in roots compared to Sehar-2006, but the Ni concentration in shoots of both the cultivars was similar. LU-26 translocated less Ni toward the shoot compared to Sehar-2006 indicating the exclusion of Ni from shoots and retaining it in roots by LU-26 as evident from bioconcentration and translocation factors. Contradictly, Sehar-2006 translocated more Ni from root to shoot indicating its tolerance to Ni. Ni increased manganese (Mn) in shoots of Sehar-2006 and LU-26 up to 60 and 30 mg kg−1, respectively. Ni decreased copper (Cu) and zinc (Zn) concentration in shoots of both cultivars, however Zn concentration in roots increased at all levels of Ni. LU-26 excluded Ni from shoots and Sehar-2006 accumulated Ni in shoots. The present study helps in understanding the process of metal uptake and distribution during the early growth stages of the plant and can signify overall potential of a crop for its exploitation on contaminated soils. [ABSTRACT FROM AUTHOR]

The use of organic amendments is a common practice in Pakistan to improve soil fertility. Organic amendments affect the chemical speciation and thus the bioavailability of heavy metals and their uptake and toxicity to plants. The present study evaluates the influence of organic amendments viz. farm yard manure (FM), poultry manure (PM), press mud (PrM) and activated carbon (AC) on nickel (Ni) bioavailability in soil, as well as its uptake into, and growth responses of, Trifolium alexandrinum. Pot experiments were conducted where T. alexandrinum was exposed to three different concentrations of Ni i.e., 30, 60 and 90 mg kg-1 in the form of NiCl2 solution in the presence and absence of organic amendments each applied at 15 g kg-1 soil. The results showed that the effect of organic amendments on Ni bioavailability and uptake by T. alexandrinum depended on the Ni concentration in the soil and the amendment type. Application of organic amendments generally increased Ni phytoavailability in soil and Ni uptake by plants at low Ni levels (Ni-0 and Ni-30) but decreased at higher levels (Ni-60 and Ni-90). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Metal contamination of the soils is a widespread problem and immobilization of metals with organic amendments is one of the different remediation technologies. We investigated the effect of activated carbon, poultry manure and pressmud on immobilization of nickel, manganese, copper, zinc, iron and lead in the contaminated soil, plant growth and metal concentrations in maize shoots. The amendments were applied to the soil at the rate of 4% on dry weight basis. Amendments significantly (P < 0.001) affected shoot dry weight and concentrations of all metals in maize shoots as compared to the control. The maximum shoot dry weight (4.54 g pot-1) was recorded with pressmud, while it was minimum with the control (2.22 g pot-1). Maize shoots contained the minimum nickel (3.54 mg kg-1) with activated carbon and the minimum concentrations of manganese (11.02 mg kg-1), zinc (48.06 mg kg-1) and iron (104.66 mg kg-1) were recorded with pressmud. Maize shoots contained the minimum concentrations of copper (25.41 mg kg-1) and lead (53.40 mg kg-1) with poultry manure and control, respectively. Amendments significantly (P < 0.001) decreased ammonium bicarbonate-diethylene triamine penta acetic acid (AB-DTPA) extractable concentrations of metals except lead. Activated carbon treated pots had minimum AB-DTPA extractable concentrations of all the metals except iron and lead. Activated carbon was most effective in immobilization of Ni, Mn, Zn and Cu decreasing AB-DTPA extractable Ni in the soil, while Fe and Pb was increased due to application of other amendments. [ABSTRACT FROM AUTHOR]

Phosphate (Pi), the fully oxidized and assimilated form of phosphorus (P), influences virtually all developmental and biochemical processes in plants; however, its availability and distribution are widely heterogeneous. Paradoxically, although total P is abundant in lithosphere, elusive soil chemistry of Pi renders the element the most dilute and the least mobile in natural and agricultural ecosystems, resulting in P deprivation due to its low mobility and high fixation capacity in the soil. NonmycorrhizalBrassicadoes not produce specialized cluster/dauciform roots but is an effective P user compared to other crops. Using a soil low in P (Mehlich 3–extractable P) with or without P fertilization,Brassicacultivars showed substantial genetic diversity in P-utilization efficiency (PUE), P efficiency (PE), P-efficiency ratio (PER), and P-stress factor (PSF). Cultivars producing greater root biomass accumulated greater total P contents, which in turn was related negatively to PSF and positively to shoot and total biomass. Plant survival and reproduction rely on efficient strategies in exploring culture media for P. Acquisition of orthophosphate from extracellular sparse P sources may be enhanced by biochemical rescue strategies such as copious H+efflux and/or carboxylates exudation into rhizosphere by roots via plasmalemma H+-ATPase and anion channels triggered by P starvation. The P-starvation-induced solution pH changes due to H+efflux, and carboxylates exudations were estimated by low-P-tolerant and low-P-sensitive cultivars in solution culture experiments. Low-P-tolerant cultivars showed more decrease in pH compared to low-P-sensitive cultivars when cultivars were grown under a P-stress environment induced by using sparingly soluble P sources (rock phosphate and tricalcium phosphate). The P contents of cultivars were inversely related to decrease in culture media pH. Low P-tolerant cultivars presented enhanced H+-efflux and total carboxylates exudations compared to low-P-sensitive cultivars, resulting in more rhizosphere acidification to scavenge Pi, evidencing their adaptability to P starvation. These elegant P-stress-induced rescue strategies by tested cultivars provided the basis of enhanced P solubilization and acquisition of P from sparingly soluble P sources to combat P-starved environments. [ABSTRACT FROM PUBLISHER]

Zinc is widespread deficient in calcareous soils and its management is more complex in reduced root-zone conditions of rice grown on saline-sodic soils. Present pot study was conducted in a wire house, Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan during 2010 to compare Zn enriched farm yard manure (FYM) with chelated (Zn-EDTA) and non chelated (zinc sulphate, ZnSO4) Zn sources for optimum grain yield and higher Zn concentration in grains of rice (cv. Shaheen Basmati) grown in a salt-affected soil. Treatments comprised of 1.5, 3 or 6 mg Zn kg-1 soil in the form of both ZnSO4 and Zn-EDTA, and Zn-enriched farm yard manure 5% of soil (w/w). Zn enrichment was done with same three levels of Zn using ZnSO4. Application of Zn increased plant growth, grain yield and Zn concentration in various tissues, irrespective of the Zn source. The increase in plant growth and Zn concentration was higher when plants were grown with Znenriched FYM compared to ZnSO4 or Zn-EDTA application alone. The maximum Zn concentration in rice grains (13.9 mg kg-1) and straw (19.1 mg kg-1) were obtained with the same treatment. It was concluded that application of ZnSO4 enriched FYM proved better over application of alone ZnSO4 or Zn-EDTA indicating the positive role of organic matter in increasing grain yield and grain Zn concentration on soils affected with salts and depleted in organic matter. [ABSTRACT FROM AUTHOR]

In developing countries, farmers use effluent as a source of irrigation and nutrients and the government takes this practice as a viable option for disposal. Sewage samples have hazardous electrical conductivities (EC), sodium adsorption ratios (SARs), and residual sodium carbonate (RSC) for irrigation, but metals were close to upper permissible limits. The EC of saturated soil paste extract (ECe) ranged from 2.18 to 4.02 dS m–1 and soil SAR 7.72 to 16.00 in soils 0.2 m deep. Average cadmium (Cd), nickel (Ni), lead (Pb), zinc (Zn), and copper (Cu) in soils ranged from 0.02 to 0.13, 0.00 to 4.45, 2.27 to 4.57, 0.71 to 13.76, and 3.17 to 10.37 mg kg–1, respectively. Plants acquired metal contents greater than in raw sewage or soils. The wide biodiversity regarding metals in shoots of natural and planted vegetation that receives raw sewage is of practical significance. It seems imperative to study under controlled conditions various plants' metal tolerance and mechanisms of metal partitioning among plant parts. [ABSTRACT FROM AUTHOR]

With more pressing demands for non-agricultural sectors, availability of good-quality water is falling short of the crop water requirement, particularly in arid and semi-arid regions of the world, like Pakistan. Studies were conducted at three sites following randomized complete block design (RCBD) with three replications. The treatments employed were: Tube well water (TW) alone; TW + Gypsum @ 50% soil gypsum requirement (TW + G50); TW-Canal water (CW) + G50; TW-CW + farm manure (FM) @ 25 Mg ha-1 (TW-CW + FM) before sowing wheat. After the harvest of wheat 2008-09, non-significant decrease in bulk density was recorded with applied treatments while infiltration rate remained unchanged. There was maximum and significant decrease in ECe and SAR with TW-CW + FM at all the three sites. Maximum decrease in ECe (72.65%) at 0-15 cm soil depth was at site 2, while maximum decrease in ECe (77.62%) at 15-30 cm soil depth was at site 1. Maximum percent decrease in SAR was 75.76% at 0-15 cm followed by 63.93% at15-30 cm at sites 2 and 3, respectively, with TW-CW + FM. Maximum wheat grain yields (3656, 3531 and 3826 kg ha-1) and straw yields (4826, 4624 and 4707 kg ha-1) were recorded at sites 1, 2 and 3, respectively, with TW-CW + FM. The net benefit was maximum with TW-CW + FM at all the three sites. [ABSTRACT FROM AUTHOR]

Once soil solution phosphorus (P) level optimum for plant growth is identified, P adsorption isotherms or their equations can further be used to estimate fertilizer P rates required to adjust this desired soil solution P level to obtain maximum yield. Surface soil samples were collected from a farmer's field area and research area. An adsorption study was conducted on Ustic Endoaquerts (S1 soil), Typic Calciargids (S2 soil), and Typic Torripsamments (S3 soil) to develop the Freundlich-type equations. Phosphorus adsorption data were obtained by equilibrating 10-g soil samples in 100 mL of 0.01 M calcium chloride (CaCl2) containing various amounts of monopotassium phosphate (KH2PO4). Values of 1/n (slope) ranged from 0.4827 to 0.6452 L kg-1. Based on 1/n values, it was inferred that each of the two S1 and S3 soils was homogeneous and S2 was not. The KF (mg P kg-1) values of S1, S2, and S3 soils were 92.45, 55.81, and 23.38, respectively. The highest amount of P (92.45 mg kg-1) was adsorbed at unit EPC in S1 soil, whereas the lowest amount (23.38 mg P kg-1) was adsorbed in S3 soil. Thereafter, 11 P fertilizer doses were calculated by these Freundlich-type equations to adjust different estimated soil solution P levels that were designated as treatments (0.05 to 0.90 mg L-1). Then field experiments on wheat (cv. Inqalab-91) were conducted according to a randomized complete block design (RCBD) on these soils to determine internal (plant tissue), external (soil solution), and fertilizer P requirements. Maximum wheat gain yield (Mg ha-1) was 6.82 with T5 (0.25 mg P L-1) on S1 soil, 5.96 with T5 (0.25 mg P L-1) on S2 soil, and 4.97 with T7 (0.40 mg P L-1) on S3 soil that was obtained by application of 196 kg P2O5 ha-1 on S1 soil, 142 kg P2O5 ha-1 on S2 soil, and 78 kg P2O5 ha-1 on S3 soil. Internal P concentration (%) associated with 95% of maximum wheat yield at booting stage was 0.32 in S1, 0.21 in S2, and 0.33 in S3 soil. In straw, it was 0.123% in S1, 0.080% in S2, and 0.108% in S3 soil. The internal P requirement of wheat grain was 0.39% in S1, 0.40% in S2, and 0.37% in S3 soil. External soil solution P requirement (ESPR) for 95% of maximum yield of wheat was 0.45 mg L-1 in S1 soil, 0.34 mg L-1 in S2 soil, and 0.44 mg L-1 in S3 soil. Quantity of P2O5 corresponding to ESPR values were 217 kg ha-1 on S1, 123 kg ha-1 on S2, and 60 kg ha-1 on S3 soil. Putting ESPR values in the respective Freundlich-type equation, P fertilizer rates (kg P2O5 ha-1) were estimated that were 282 on S1, 167 on S2, and 83 on S3 soil; Practically, 262, 156, and 78 kg P2O5 ha-1 was applied in the field to adjust soil solution P level (mg L-1) at 0.40 (T7), 0.30 (T6), and 0.40 (T7) in S1, S2, and S3 soil, respectively, that are somewhat less than determined ESPR values. Phosphorous doses applied to achieve a desired EPAS value or estimated from graphs against predicted ESPR values, or calculated from corresponding Freundlich-type equations using desired ESPR values are in close proximity to one another. Therefore, any of the techniques can be used interchangeably to estimate the P fertilizer requirement for optimum wheat yield. [ABSTRACT FROM AUTHOR]