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Climate change and salt-affected soils detrimentally affect crop production in arid regions. Reclaiming these soils for crops and carbon sequestration can mitigate climate change and enhance food security. A laboratory-scale experiment was conducted on a wheat-maize crop rotation system for three consecutive years to check the effectiveness of organic amendments in reclaiming marginally salt-affected soils, improving soil health, sequestering carbon, and improving food grain production. This study included five treatments namely control (T1), gypsum alone at 100% gypsum requirements (G100), and its combinations with different organic amendments and 50% gypsum requirements (farm manure (FYM+G50), poultry manure (PM+G50), and green manure (GM+G50)) were used. Results indicated that sandy clay loam textured soil showed highest potential for its properties improvement after 45 days, i.e., EC decreased up to 3.9 dS m−1, pH 7.9 and, SOC increase up to 0.25%. After the fallow period, three consecutive years of crop production study indicated up to 39 and 70% increase in wheat and maize yields, respectively, compared to inorganic fertilizer alone. Maximum soil aggregation was noted in treatment with gypsum and farmyard manure application in loam soils (50%). The maximum soil organic carbon accumulation over the whole experiment was recorded in farmyard manure application in combination with gypsum (0.44 g kg−1) in both loam and sandy clay loam soil, while 0.31 g kg−1 in the clay loam soil. Based on the results, it was concluded that reclaiming marginally salt-affected soils enhances food crop production and incorporating manures improves soil through aggregation and carbon sequestration, mitigating climate change. [ABSTRACT FROM AUTHOR]

The uncontrolled concentrations of heavy metals introduced into the water sources need an effective method for their removal. The dithiocarbamate (dtc) ligands are the most popular precipitating agents used for the removal of metals from wastewater. Presently, two novel dtc ligands, one without methylene linker (K2L1) and the other with methylene linker (K2L2) were used for the removal of eight heavy metals ions including Fe2+, Co2+, Ni2+, Cu2+, Cd2+, Ag+, Zn2+ and Pb2+ from the aqueous solution. These dtc ligands contain acyl (NH-C = O) and S, S (thiolate) functional groups. The results indicated that the metal removal efficiency of both ligands was almost 100% at pH 4 and 7 and free of the linker effect and acyl functional groups but depends on the S, S binding sites. It exhibited a distinct selectivity for the removal of metal ions (Pb2+ ∼ Cu2+ ∼ Ag1+ > Cd2+ > Co2+ > Ni2+ > Zn2+ > Fe2+). The developed methods have the potential for the removal of heavy metals and can be used for other thiophilic metals that are water-soluble. HIGHLIGHTS Water treatment, contaminated by heavy metal ions. Synthesis and characterization of two novel dithiocarbamate ligands. Effect of methylene (-CH2-) linker of dithiocarbamtes on heavy metals extraction. pH and temperature effect on the extraction efficiency of ligands. [ABSTRACT FROM AUTHOR]

We conducted a pot experiment to evaluate the potential for soil- and foliar-applied silicon (Si), alone and in combination, to a Cd-contaminated soil in order to evaluate the effects on such amendments on the Cd translocation from soil to wheat root, shoot and grains. Five treatments were used, T1) control with no external factor added, T2 received only Cd, while T3–T5 treatments received Cd in combination with soil, foliar and soil plus foliar applied Si. Except control (T1), soil was contaminated with Cd at 10 mg kg−1 in all the treatments and 1% solution of Si as an amendment was used for soil and/or foliar application or their combination. Overall, while Si application improved both plant growth and yield in Cd-contaminated soil. Control and combined soil- and foliar-applied Si in Cd contaminated treatments showed equally positive (2.5%) increase in plant height over Cd contaminated treatment. Grain yield was also highest in the treatment receiving Cd plus soil-applied Si (29%) followed by control (26%). It was concluded that Si can alleviate Cd toxicity in wheat irrespective of whether the Si was soil-applied or applied via a foliar method, but soil applied Si proved the best in this regard. Novelty statement Immobilization of metals i.e., cadmium (Cd) with soil-applied amendments like biomaterials and organic manure to decrease Cd concentration in plants have already been widely investigated. Silicon (Si) is a cheap in-organic and readily available element in the nature and also used for the same purpose. It can be applied both in soil as well as by foliar and soil + foliar application to decrease the metals concentration in soil and plants. However, comparative effectiveness of these three methods have not been checked simultaneously. In this study, we have studied the comparative effectiveness of Si application to soil, foliar and their combination (soil + foliar) to decrease Cd concentration during wheat crop. [ABSTRACT FROM AUTHOR]

We investigated the role of ascorbic acid (AsA) to alleviate nickel (Ni) induced adverse effects on growth and concentration of Ni, copper (Cu), and manganese (Mn) in hydroponically grown wheat varieties viz. Galaxy, Punjab-2011, and FSD-08. Plants were exposed to five levels of Ni viz. 0, 5, 10, 15, and 20 mg L−1. After 1 week, AsA (1 mM) was sprayed onto the Ni-stressed plants. FSD-08 produced the maximum SDW with and without AsA compared to other varieties. FSD-08, Galaxy, and Punjab-2011 witnessed 2.61-, 2.83-, and 7.5-fold increases in SDW with AsA, respectively. Wheat plants contained the maximum Ni in shoots and roots with a Ni level of 20 mg L−1 irrespective of varieties. Nickel in shoots decreased with AsA witnessing 13, 12, and 10% decrease in FSD-08, Punjab-2011, and Galaxy, respectively. Nickel in roots of FSD-08 decreased by 18% while increased by 3.34-fold and 3.50-fold in Galaxy and Punjab-2011, respectively with AsA. Nickel decreased Cu in shoot and Mn in shoot and root while Cu in roots of all wheat varieties increased. It was concluded that AsA improved the growth of Ni-stressed and FSD-08 performed better by maintaining good growth and less Ni in shoots compared to other varieties. Exploiting plant internal mechanisms with foliar application of different organic substances have widely been investigated to decrease metal accumulation and their adverse effects on plants. However, the differential response of different varieties to metal accumulation in response to foliar application of ascorbic acid is not well documented. This study was conducted to investigate the effect of exogenous application of ascorbic acid on growth response, the concentration of Ni, Cu, and Mn in three wheat varieties. [ABSTRACT FROM AUTHOR]

Afforestation is one potential action for improving the environment from local to global scales. Deforestation plagues many regions of the world and in recent times, there are ongoing efforts by some countries to expand afforestation programs. One key decision in the design of afforestation programs is species selection. Here, we demonstrate species selection for afforestation using two different multi-criteria decision-making (MCDM) techniques. The study covers two regions within the Khyber Pakhtunkhwa province of Pakistan and is based on their ongoing project, the Billion Tree Tsunami. We considered six criteria for decision making. These criteria included cost, reproducibility, growth rate, environmental compatibility (including soil compatibility, temperature, rainfall requirements), environmental effects (including transpiration rate, evergreen or not, soil erosion control) and uses (medical, constructional and fodder). The results of both MCDM methods were comparable, suggesting that our findings are acceptable and consistent. The study is useful for the forestry department at local and international levels. Additionally, it is informative for researchers and readers with an interest in the application of MCDM in forestry. [ABSTRACT FROM AUTHOR]

Phosphorus (P) deficiency is an important nutritional constraint for crop productivity in alkaline-calcareous saline-sodic soils. Generally, farmers apply different P fertilizers to overcome P deficiency; however, different P fertilizers may have different efficiency in saline-sodic and normal soils. An experiment was conducted to investigate the comparative effect of phosphatic fertilizers, viz. single super phosphate (SSP), di-ammonium phosphate (DAP) and triple superphosphate (TSP), on the growth of rapeseed. These fertilizers were applied to three different types of soils, viz. normal, saline-sodic soil-I {EC, 7 dS m−1; SAR, 25 (mmol L−1)1/2} and saline-sodic soil-II {EC, 14 dS m−1; SAR, 50 (mmol L−1)1/2). In normal soil, DAP was effective to enhance growth compared to other fertilizers. In saline-sodic soil-I, SSP enhanced shoot dry weight (SDW) to the maximum (51%) compared to control and by 12% and 21% compared to TSP and DAP, respectively. In saline-sodic-II, SSP increased SDW by 51% compared to control and by 14% and 20% compared to TSP and DAP, respectively. In saline-sodic soil-I, SSP-fertilized plants had 22% and 7% higher membrane stability index compared to plants grown with DAP and TSP. In saline-sodic soil-I and II, plants grown in pots fertilized with SSP accumulated the maximum chlorophyll contents, while control plants contained the minimum. In saline-sodic soils, SSP increased P concentration in shoot and Olsen P compared to other fertilizers. It is concluded that SSP is relatively more effective and improves plant growth in saline-sodic soils, while DAP is suitable for normal soils. [ABSTRACT FROM AUTHOR]

Shifting toward stress-resistant planting material has become a pre-requisite for fruit tree culture under arid to the semiarid environment. No information currently exists on the physiological basis of water stress tolerance in Ziziphus jujuba at the saplings stage, an important fruit tree of semiarid regions of Central Punjab. Therefore, an experiment was conducted under controlled conditions where plants were subjected to three watering regimes: control irrigation, a medium, and a high-water deficit treatment. During the experiment, growth, biomass production and allocation in different plant organs (leaves, stem, and root) were measured. The physiological response of Z. jujuba under water deficit was determined through a gas exchange system and CO2 assimilation rate, stomatal conductance, and water use efficiency were evidenced. Biomass production/allocation in leaves and stem decreased significantly with an increase in soil water deficit. Root biomass production remained unchanged (p = 0.907), but allocation increased significantly under high soil water deficit (p < 0.001). Net CO2 assimilation rate (A) remained similar at 6.54 ± 0.32 μmol m−2 s−1 but, stomatal conductance (gs) decreased significantly from 94.0 to 69.2 mmol m−2 s−1 under high water deficit treatment. Water use efficiency (ratio between Net CO2 assimilation rate and transpiration rate) also increased significantly (p = 0.012) under high water deficit treatment. Ziziphus jujuba showed a medium degree of plasticity under water deficit conditions, which was mainly driven by a sustained CO2 assimilation rate and more biomass allocation for root development. [ABSTRACT FROM AUTHOR]

The aim of this study was an in-situ synthesis of hydroxyapatite (HA) on cellulose fibers to be used as a new reinforcing agent for dental restorations. The microwave irradiation method was used for synthesis and the materials were characterized with analytical techniques. The prepared dental resin composites were mechanically tested by a universal testing machine and electrodynamic fatigue testing system. FTIR, XRD, SEM/EDS analysis confirmed the successful synthesis of HA on cellulose fibers. The Alamar blue biocompatibility assay showed more than 90% cell viability for the prepared cellulose/HA. The mechanical properties of resin composites improved with cellulose content from 30 wt.% to 50 wt.% in the polymer matrix. Substantially, increasing the cellulose/HA content from 40% to 50% improved the mechanical properties. The results suggested that HA could be successfully synthesized on cellulose fibers using microwave irradiation and contributed to improving the mechanical properties of dental resin composites. [ABSTRACT FROM AUTHOR]

The effect of organic amendments on phytoavailability of nickel (Ni) and other metals in soil may change with time due to transformation of organic matter. We investigated the residual effect of organic amendments (farm manure [FM], poultry manure [PM], pressmud [PrM], and activated carbon [AC]) to immobilize Ni and other metals in soil and absorption of metals by Egyptian clover. Fresh and dry weights of Egyptian clover increased significantly (p < 0.05) due to residual effect of amendments compared to control. Extractable Ni and other metals had significant positive correlation with residual organic matter in soil. Extractable manganese (Mn) in post-harvest soil of Egyptian clover increased compared with that of post-harvest soil of maize (previous crop). However, extractable copper (Cu) decreased with amendments. Copper was the maximum in control followed by AC. Zinc in soil decreased in FM and PrM treated pots but increased in pots amended with PM and AC. Concentration of Ni, Mn, and Cu was the minimum in shoots of those plants grown with AC amended pots compared to the control. It was concluded that AC was the most effective for immobilization of metals in soil which consequently decreased the concentration of metals in shoots of Egyptian clover. [ABSTRACT FROM AUTHOR]

Pakistan Railways has faced a severe financial crisis in recent years. Pakistan has recently become a partner with China in a mega-investment project under an agreement called the China-Pakistan Economic Corridor (CPEC). Among other things, CPEC also includes a range of investments in Pakistan Railways. This particular study focuses on the analysis of US$8.2 billion investment in the upgrade and expansion of the Karachi-Peshawar railways link, which is also known as the ML-1 (Main Line 1). The study found ML-1 as economically viable with a payback period of 10 years. Furthermore, ML-1 project investment is expected to result in uplifting Pakistan Railways, mainly through an increase in freight and passenger transportation. Some risk factors may hinder the expected economic return from the CPEC investment in Pakistan Railways. These factors include consistency in the government policies, the status of the Pakistani economy in upcoming years, and law and order situations in the country. The study has a utility for the governments of both countries and larger business communities have stakes in the trade between the two countries. It is equally beneficial for the international community, businesses (both in China and Pakistan) and locals of the region associated with the CPEC infrastructure. [ABSTRACT FROM AUTHOR]

Construction is commonly regarded as one of the major industries of an economy that is receiving a significant attention in the developing countries. This paper uses the Asian Development Bank (ADB) input-output database at constant prices for the selected Asian countries, i.e. Bangladesh, Sri Lanka and Nepal to analyze and compare the performance of the construction sector in these economies. The novelty of this research is the application of multiple linkages methods. First, the standard measures of the backward and forward linkages are used to examine the induced output created by the demand push and supply pull effects of the construction industry. Second, the concept of Hypothetical Extraction Method (HEM) is applied to extract a sector hypothetically from an economic system and then to examine the influence of that extraction on the rest of the economy. The results indicate that the construction sector has a strong backward and weak forward linkages for all the three economies. Furthermore, results reveal that the 'pull effect' is very significant in these countries while the 'push effect is very insignificant. With respect to the identification of the key sectors, the findings of the traditional methods are very different from those of the hypothetical extraction methods. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) phytoremediation potential and its accumulation in edible and nonedible plant tissues is the function of various biochemical processes taking place inside plants. This study assessed the impact of organic ligands on Cd phyto uptake and different biophysiochemical processes of Spinacia oleracea L., and associated health hazards. Plants were exposed to Cd alone and chelated with citric acid (CA) and ethylenediaminetetraacetic acid (EDTA). Results revealed that the effect of Cd on lipid peroxidation, H2O2 production and pigment contents varied greatly with its applied level and the type of organic ligand. Moreover, the effect was more prominent in root tissues than leaf tissues and for high concentrations of Cd and organic ligands. Cadmium accumulation increased by 90 and 74% in roots and leaves, respectively, with increasing Cd levels (25–100 µM). Cadmium exposure at high levels caused lipid peroxidation in roots only. Application of both CA and EDTA slightly diminished Cd toxicity with respect to pigment contents, lipid peroxidation and hydrogen peroxide (H2O2) contents. Hazard quotient (HQ) of Cd was <1.00 for all the treatments. Under nonlinear effect of treatments, multivariate analysis can be an effective tool to trace overall effects/trends. [ABSTRACT FROM AUTHOR]

A 2-year field experiment was conducted to determine crop yield and N use efficiency (NUE) from a saline–sodic soil (clay loam) with and without application of gypsum. Treatments included two N application rates (15% and 30%) higher than the recommended one to the normal soil, and gypsum added at 50% and 100% of soil gypsum requirement (SGR) to the saline–sodic soil, both cultivated with rice and wheat during 2011–2013. Results revealed a decrease in pH of saturated soil paste (pHs), electrical conductivity of saturation extract (ECe), sodium adsorption ratio (SAR) and exchangeable sodium percentage with N fertilizer along with gypsum application in saline–sodic soil. However, the effect was most prominent when gypsum was added at 50% of SGR. Crop yield and NUE remained significantly lower (p < 0.05) in saline–sodic-soils as compared to normal soil. However, gypsum application reduced this difference from 47% to 17% since both yield and NUE increased considerably. Crop yield and NUE remained higher for wheat than for rice. During first year, higher doses of N with gypsum application at 50% SGR proved most effective, whereas, in subsequent year, recommended N along with gypsum at 50% SGR became more profitable. All these results lead us to conclude that gypsum application can ameliorate saline–sodic soil thereby increasing crop yield and NUE. [ABSTRACT FROM AUTHOR]

The present study deals with the effects of addition of sulfur along with other acidifying agents for their ability to lower and maintain the pH in a given range for a longer period of time. The chemicals were subjected to batch test individually and in combinations. Treatments were applied to three soils of different textures: sandy clay loam, clay loam, and silt loam. A 1:1 soil/water paste along with the added amendment was maintained at room temperature for 2 months. Most of the chemical treatments lowered the pH significantly. Combinations containing S/Al2(SO4)3/H2SO4, S/Al2(SO4)3/H2O2, and S/H2O2/H2SO4were found to be very effective in lowering the pH. The soil pH remained acidic for 2 months, indicating the suitability of chemically amended soil for the plantations requiring acidic soil pH. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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]

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]

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]

Plants have adapted a number of mechanisms to cope with widespread phosphorus (P) deficiency in arable lands. Crop species and even cultivars differ widely in one or more of these adaptive mechanisms hence, in P efficiency. Identification of these mechanisms is pre-requisite for long term breeding programs. Two independent experiments were conducted to study the possible mechanisms of P efficiency in Brassica cultivars. Eight Brassica cultivars (‘B.S.A.’, ‘Toria’, ‘Toria Selection’, ‘Brown Raya’, ‘Peela Raya’, ‘Dunkeld’, ‘Rainbow’, and ‘CON-1’) were selected on the basis of differences in growth under P deficiency from preliminary experiment. In the first experiment, cultivars were grown for 40 days in sand supplied either with sparingly soluble phosphate rock (PR) or soluble mono-ammonium phosphate (MAP). Cultivars differed significantly (P<0.05) for biomass production, P contents and P use efficiency. Low P availability in PR treatment resulted in significantly lower dry weights and P contents than those grown with MAP. The cultivars ‘Rainbow’, ‘Brown Raya’ and ‘Dunkeld’ accumulated more biomass (3.2 g/pot) and P contents (3.0 mg/pot) than other cultivars when grown with PR. Root dry weight was significantly correlated with shoot dry weight, shoot P content and total P content (r > 0.65) indicating significance of improved root growth for P acquisition. While in the second experiment cultivars were grown with adequate P for 30 days and then P was withdrawn from the nutrient solution by replacing fresh P free nutrient solution for 10 days. Induced P deficiency increased P contents in young leaves by two folds indicating remobilization of P from older leaves and shoot. Nonetheless cultivars varied for remobilization but differences in P remobilization could not explain the differences in P utilization efficiency among cultivars. Hence further experimentation to study root morphology, P uptake, and organic acid exudation by these cultivars in relation to P deficiency is recommended. [ABSTRACT FROM PUBLISHER]

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]

The large genotypic variation for salt tolerance in rice and wheat is the driving force behind efforts to identify appropriate cultivars for salt-prone environments where large variations in salinity (electrical conductivity, EC) and sodicity (sodium adsorption ratio, SAR) levels exist. An evaluation of the commonly grown rice and wheat cultivars at different EC/SAR ratios may thus help in coping with the crop failures on salt-affected soils. Accordingly, we evaluated some salt-tolerant cultivars of rice and wheat for growth and yield at different soil salinity and sodicity levels in a sandy clay loam soil. Among the cultivars tested, rice 'SSRI-8' produced the highest productive tillers and paddy yield, and wheat cultivar 'SIS-32' produced the highest tillers and grain and straw yields. The high EC/SAR ratios proved more hazardous for rice than for wheat. Irrespective of the varieties tested, the highest levels of EC and SAR (T5 and T6) caused significant reduction in paddy yield, whereas at the lowest levels of EC and SAR (T1 and T2), paddy yield was not affected significantly when compared with the control. However, in case of wheat crop, all the levels [i.e., the lowest (T1 and T2), medium (T3 and T4), and the highest (T5 and T6) of EC and SAR tested] affected wheat yield adversely with significant differences. For both the crops, there were little or no differences in yield between the two ratios tested (i.e., 1:2 and 1:4) at all the levels of EC and SAR. [ABSTRACT FROM AUTHOR]