Effects of Lead Forms and Organic Acids on the Growth and Uptake of Lead in Hydroponically Grown Wheat

This study investigated the effects of lead (Pb) form (free or complexed) and type and concentration of chelants [citric acid and ethylenediaminetetraacetic acid (EDTA)] on the growth and ability of wheat to accumulate Pb. Wheat variety Auqab-2000 was exposed to four levels of EDTA and citric acid (0, 500, 1000, and 1500 μM) in the presence of Pb (1000 μM). Both the free Pb (1000 μM) and high concentration (1500 μM) of EDTA and citric acid reduced the plant biomass. Without the addition of chelants, only a little Pb was accumulated by wheat shoots. This demonstrates that organic acids used in enhanced phytoextraction applications do not merely serve to increase metal mobility and plant availability but also can help to increase translocation rates of metals absorbed by the plant roots. Greater translocation of Pb from roots to shoots was observed with EDTA than that with citric acid.     

Effect of phosphorus deficiency and seasonal variations on growth and essential oil content of Japanese mint(M. Arvensis L. Var. Piperascens)

In a previous communication from this laboratory it has been indicated that mint plants respond typically to different environmental conditions (day length and temperature) by marked alterations in growth, and synthesis of essential oil (SINGH and SINGH, 1968a (1)). Similar work on M. piperita L. carried out by several workers clearly shows that the mineral nutrition and metabolism of this plant are equally affected by environmental changes (CRANE and STEWARD, 1962 (2) ; RABSON, 1965 (3) ; STEWARD et al. 1959 (4)), and the metabolic consequences which flow from deficiencies of nutrient elements are greatly influenced by these factors, e. g., lack of phosphorus under short days is accompanied by greater accumulation of amides than under long days and, therefore, causes decrease in other soluble constituents, viz. amino acids (CRANE and STEWARD, 1962).     

Effects of Topographic Factors of the Site on the Essential Oil Compounds of Artemisia aucheri Aerial Parts Grown in a Mountainous Region

In this study, the chemical compositions of the essential oils from the aerial parts of Artemisia aucheri, grown in a mountainous region in Ghamsar Province, central Iran, have been analyzed by using gas chromatography (GC)–mass spectroscopy (MS) to determine how they are affected by topographic factors (site direction and elevation). Plants were sampled at random in full flowering stage in a completely randomized (CR) design with three replications. The essential oil was extracted by a modified Likens–Nickerson's simultaneous distillation–extraction (SDE) technique. Analysis of the plant oils on the sites [in two directions, north–south (N/S) and east–west (E/W)] and five elevations resulted in 30 identified compounds. Of the oil samples collected, the 99.94% of the components at the N/S site and 99.89% at the E/W site were identified. The main component in the two directions (N/S and E/W) was α-thujone with 19.5% and 18%, respectively. Other significant components in the two directions include α-pinene, davanone, camphor, and camphene. The percentages of all these main compounds on the N/S site were more than on the E/W site. Also, the main compounds increased with increasing altitude and at all five elevations. Among all the oil compounds, the percentages of α-thujone, α-pinene, and camphor were the greatest. Finally, at all the elevations, the percentage of the α-thujone was the greatest among the different oil compounds.     

Fate of Carbon in Water-Stable Aggregates during Decomposition of 13C-Labeled Corn Straw

Fundamental knowledge about decomposition, fate of crop residue, and allocation of residue-derived carbon (C) in soil aggregates is essential to understand the C dynamics in soil. The incorporation of C derived from corn residue in water-stable aggregate fractions, particulate organic C (POC), and mineral-associated C (MAC) in soil were examined using the ¹³C tracer technique. Soil was treated with corn straw at the rate of 1% dry mass of soil brought to 66% of field capacity and incubated for 70 days at 25 °C. Samples were taken at 20, 35, and 70 days and analyzed for water-stable aggregates. Values for POC and MAC were analyzed for total C and ¹³C enrichment. The addition of corn straw caused a shift in the distribution of recoverable particles with significant decreases in <53-μm silts and clays, microaggregrates (53–250 μm), and smaller macroaggegates (250–2000 μm); however, the large macroaggegates (>2000 μm) increased significantly. Macroaggregates contained greater amount of C than microaggregates. The proportion of ¹³C recovered in the fractions <53 μm (silt and clay), 53–250 μm, and 250–2000 μm increased during decomposition of corn straw, whereas there was no significant change in >2000-μm fraction. Most (70–76%) of the soil organic C was affiliated with MAC (<53 μm). Carbon (¹³C) derived from corn straw decreased in POC but increased in MAC as decomposition proceeded. In the long term, microaggregate fraction appears to be involved in storage and stabilization of the C derived from corn straw and is important for soil quality and soil C sequestration point of view.     

Potential of zinc seed treatment in improving stand establishment,phenology, yield and grain biofortification of wheat

Abstract

One of the problems in obtaining high wheat yield is the unavailability of micronutrients in balanced quantities. Zinc is an essential micronutrient due to its involvement in many metabolic processes in plant. In this experiment, seeds of two wheat cultivars (Faisalabad-2008 and Lasani-2008) were subjected to soak in aerated Zn solution of 0.1 and 0.01?M for 12?hr. For the seed coating, Zn was adhered to the wheat seeds by using Arabic gum by using zinc sulfate (ZnSO₄·7H₂O) as a source. Untreated dry seeds were considered as a control. Results indicated that field emergence was improved by Zn seed treatments, maximum numbers of seedlings were observed in seed priming with 0.01?M Zn solution. Seed osmoprimed with 0.01?M Zn solution improved the grain yield, biological yield, and other yield related traits. Grain and straw Zn enrichment were also enhanced in seed osmoprimed with 0.01?M Zn solution.     

Alleviation of manganese toxicity and manganese-induced iron deficiency in barley by additional potassium supply in nutrient solution

Barley plants were grown hydroponically at two levels of K (3.0 and 30 mm) and Fe (1.0 and 10 μm) in the presence of excess Mn (25 μm) for 14 d in a phytotron. Plants grown under adequate K level (3.0 mm) were characterized by brown spots on old leaves, desiccation of old leaves, interveinal chlorosis on young leaves, browning of roots, and release of phytosiderophores (PS) from roots. These symptoms were more pronounced in the plants grown under suboptimal Fe level (1.0 p,M) than in the plants grown under adequate Fe level (10 μm). Plants grown in 10 μm Fe with additional K (30 mm) produced a larger amount of dry matter and released less PS than the plants grown under adequate K level (3.0 mm), and did not show leaf injury symptoms and root browning. On the other hand, the additional K supply in the presence of 1.0 μM Fe decreased the severity of brown spots, prevented leaf desiccation, and increased the leaf chlorophyll content, which was not sufficient for the regreening of chlorotic leaves. These results suggested that the additional K alleviated the symptoms of Mn toxicity depending on the Fe concentration in the nutrient solution. The concentration (per g dry matter) and accumulation (per plant) of Mn in shoots and roots of plants grown in 10 μm Fe and 30 mm K were much lower than those of the plants grown in 10 μm Fe and 3.0 mm K, indicating that additional K repressed the absorption of Mn. The concentration and accumulation of Fe in the shoots and roots of the plants grown in 10 μm Fe and 30 mm K were higher than those of the plants grown in 10 μm Fe and 3.0 mm K, indicating that the additional K increased the absorption of Fe under excess Mn level in the nutrient solution. The release of PS, chlorophyll content, and shoot Fe concentration were closely correlated.     

Analyzing the Relation between Loss-on-Ignition and Other Methods of Soil Organic Carbon Determination in a Tropical Cloud Forest (Mexico)

The objective of this study was to analyze the relationship between soil organic carbon content, determined by dry combustion (%OC_LECO) and the Walkley–Black method (%OC_WB), and loss on ignition (LOI). Soil samples were collected from noncalcareous O and A1 horizons within a tropical cloud forest. Linear regression equations were developed to estimate organic carbon from LOI. The applicability of the predictive equations was evaluated by comparison of measured and predicted organic carbon data for independent soil samples. The results showed that the LOI method produced a better linear relationship with the %OC_LECO (R ² = 0.96, P < 0.001) than with the %OC_WB (R ² = 0.88, P <0.001) method. These results also showed that %OC_WB and %OC_LECO prediction equations underestimate and overestimate soil organic carbon by 0.74% and 0.56%, respectively. This study suggests that LOI may be a good estimator of soil organic carbon for noncalcareous O and A1 horizons in a tropical cloud forest.     

Suitability of extractant for soil available silicon and silicon response to upland paddy grown on alkaline soils of central India

Abstract

Several silicon (Si) extractants are being employed in different countries mostly for lowland acidic soils. Present investigation was conducted to evaluate suitable extractants for upland paddy grown on alkaline soils. Available Si was extracted by using ten different extractants. Tris buffer pH 7.0 (1:10) in Inceptisols showed positively highest and significant correlation with grain yield (r?=?0.870), grain Si uptake (r?=?0.887), straw yield (r?=?0.852), and straw Si uptake (r?=?0.919). However, 0.5?M acetic acid (1:2.5) in Vertisols showed positively highest and significant correlation with grain yield (r?=?0.810), grain Si uptake (r?=?0.852), straw yield (r?=?0.850), and straw Si uptake (r?=?0.929). The application of Si @ 200?kg ha^?1 along with chemical fertilizers significantly increased yield and nutrient uptake of upland paddy on Vertisols. Tris buffer pH 7.0 (1:10) and 0.5?M acetic acid (1:2.5) were suitable extractant for Inceptisols and Vertisols, respectively based on its correlation with yield and nutrient uptake.     

Evaluation of Chemical Extractants for the Determination of Available Potassium

Abstract

Evaluation of nutrient status in soil is important for nutritional, environmental, and economical aspects. This research was carried out to determine the potassium (K) available to corn (Zea mays) in 15 soils from the Hamedan province in the west of Iran. The treatments included two K levels [0 and 200 mg K kg^?1 as potassium sulfate (K₂So₄)] and 15 soils in a factorial experiment in a randomized block design with three replications. The results indicated that K application increased yield, K concentration, and K uptake of corn. According to the mechanism of the extraction, these extractants can be classified into four groups. The first group of extractants, acidic extractants, includes 0.02 M strontium chloride (SrCl₂)+0.05 M citric acid, 0.1 M hydrochloric acid (HCl), and Mehlich 1. The second group includes 0.1 M barium chloride (BaCl₂), 0.01 M calcium chloride (CaCl₂), and 1 M sodium acetate (NaOAc). The third group includes 1 M ammonium acetate (NH₄OAc), ammonium bicarbonate–diethylenetriamine tetraacetic acid (AB‐DTPA), and finally distilled water. The results showed that correlation between extractants in each groups were significantly high. Correlation studies showed that NH₄OAc and AB‐DTPA cannot be used as available K extractants. The correlation of other extractants with relative yield, plant response, and K uptake were significantly high. Therefore, these extracting solutions can be used as available K extractants.

Potassium critical levels by extractants were also determined using the method by Cate and Nelson (1971) Cate, R. B. and Nelson, L. A. 1971. A simple statistical procedure for partitioning soil test correlation into two classes. Soil Science Society of America Proceeding, 35: 658–660. [Crossref], [Web of Science ®] , [Google Scholar]. Potassium critical levels for 90% relative yield were 29, 27, 82, 84, 45, 145, and 272 mg kg^?1 for 0.002 M SrCl₂, distilled water, 0.02 M SrCl₂+0.05 M citric acid, 0.1 M HCl, Mehlich 1, 1 M NaOAC, and 0.1 M BaCl₂, respectively.     

Occurrence of 4-methyleneglutamine and 2-oxo-4-methyl-3-pentene-1,5-dioic acid in leaves and stem of tulip plants

Abstract

The presence of 4-MeGln in the tulip plant was discovered by ZACHARIUS et al. (1954), and it was found that this amide generally occurred in the leaves of almost all the species of genus Tulipa (FOWDEN and STEWARD 1957a). The 4-MeGln compound has been detected in every part of the tulip plant, i.e., bulb scales, roots, basal plate, young shoots, leaves, stern, and flower (FOWDEN and STEWARD 1957a, b; OHYAMA 1986; OHYAMA et al. 1985, 1988a, b; ZACHARIUS et al. 1954, 1957). Especially 4-MeGln was found to be a major soluble N constituent in the leaves and stem of tulip of the flowering stage (OHYAMA et al. 1985; OHYAMA 1986).     

Die Anwendung der Ertragskurvenberechnung nach von Boguslawski und Schneider bei der Auswertung aktueller N-Steigerungsversuchsserien

Abstract

Yield curve calculation according to von BOGUSLAWSKI and SCHNEIDER as well as the EDP calculating programme, derived from it by Horst and Heyn (1988 Horst H Heyn J 1988 Ein PC-Programm zur Errechnung von Ertragskurven nach der dritten Annäherung an das Ertragsgesetz von v. Boguslawski und Schneider LUFA Kassel, hausintern  [Google Scholar]) and later also Kowert (2001 Kowert A 2001 Erstellung eines PC-Programmes zur Ermittlung von Ertragskurven bei Düngungsversuchen Diplomarbeit FH Osnabrück, FB Agrarwissenschaften, Studiengang Landwirtschaft  [Google Scholar]), are described. With the version at hand objective and reproducible results can be calculated in a fast and user-friendly way.

This program enables an exact definition of the maximum yield and the best fertilisation required; also every yield value on the basis of a given amount of nutriment can be deduced. Thereby results of tests and series with differing variations can be offset against each other together. Like this wide research series with accordingly high significance can be evaluated. Of course other parameters can be calculated in addition to the yield, too.

This yield curve calculation is particularly suitable for the evaluation of research on N-increase. Considering Hessian research on winter wheat, winter barley, winter rye, rape seed and sugar beet as example, the effects of increasing mineral N-fertilisation on the yield, the adapted financial gross earning and the N-removal with the main product of a crop are indicated.

The N-fertilisation aiming at the greatest natural yield of the tested fruit winter wheat, winter barley, winter rye, rape seed and sugar beet, requires an amount of about 145 to 225 kg N/ha. The economical optimisation of the N fertilisation is about 30 to 40 kg/ha lower with cereals compared to about 90 kg/ha lower with rape and sugar beet.

The optimisation of the N-fertilisation as to the financial gross earning leads to a significant increase of the supply-removal-account into an uncritical range for all fruits. The amount of the N-fertilisation should not be fixed on the natural yield, but on parameters of cost-effectiveness. This leads to economical and ecological advantages.     

Interaction effect of nitrogen,phosphorus, and zinc fertilization on growth,yield, and nutrient contents of aromatic rice varieties

Abstract

Studies on nutrient interactions in aromatic rice are needed for proper understanding of impact of imbalanced use of nutrients in the era of multi and micro-nutrient deficiencies. A pot experiment was conducted during the rainy/wet season (June–October) of 2013 at New Delhi, to study the interaction effects of two levels each of nitrogen (N) (0 and 120?kg?ha^?1), phosphorus (P; 0 and 25.8?kg?ha^?1), and zinc (Zn; 0 and 5?kg?ha^?1) in two aromatic rice (Oryza sativa L.) varieties, viz. Pusa Rice Hybrid 10 and Pusa Basmati 1121. Application of N, P, and Zn resulted in increase of dry matter (0.91, 0.32, and 0.24?g plant^?1, respectively) 60?days after sowing (DAS) and grain yield of rice (3.68, 1.67, and 1.17?g plant^?1). The increase in yield of rice owing to N application was relatively higher by 0.98, 0.22, and 1.05?g plant^?1, respectively, when either P or Zn or both were applied with N than alone application of N, indicating synergetic effect of P and Zn application with N. The higher concentration and uptake of K in grain (0.25% vs 0.10%) and straw (1.32% vs 0.94%) were observed in the treatment received N than no N, though K was applied uniformly in all the treatments. It indicates positive interaction of N and K. The higher uptake of P in grain and straw was observed when P was applied with N and Zn (3.34 and 2.15?mg plant^?1), or with N (3.26 and 2.11?mg plant^?1) signifying positive effect of N on P uptake in rice.     

Phosphorus Fertility Assessment of Intensively Farmed Areas of Catchments Draining to the Great Barrier Reef World Heritage Area; 2: Potential of Soils to Release Soluble Phosphorus

Abstract

The potential of fertilized cropping soils (sugarcane, vegetables, fruit trees) in river catchments that drain to the Great Barrier Reef World Heritage Area in northeastern Australia to release soluble phosphorus (P) was assessed using soil chemical tests on typical soils (0–10 cm) collected in 2003. Tests included total P, diagnostic soil P tests, estimates of P buffering, and soluble and redox sensitive soil P. Routine soil P tests proved poor predictors of CaCl₂ P (0.005 M). Values≥0.20 for the Mehlich‐3 P saturation ratio separated (P<0.01) lower from higher concentrations of CaCl₂ P. The ratio of Mehlich‐3 Fe to [Mehlich‐3 Fe+Mehlich‐3 Al] is offered as a possible simple index of redox sensitive P. Part 1 (Rayment and Bloesch 2006 Rayment, G. E. and Bloesch, P. M. 2006. Phosphorus fertility assessment of intensively farmed areas of catchments draining to the Great Barrier Reef World Heritage Area, 1: Soil phosphorus status. Communications in Soil Science and Plant Analysis, : 37 [Google Scholar]) describes the soil survey in more detail.     

Salt tolerance of Casuarina equisetifolia and Frankia Ceq1 strain isolated from the root nodules of C. equisetifolia

Effects of NaCl on the seed germination and growth of Casuarina equisetifolia seedlings and multiplication of the Frankia Ceq1 strain isolated from the root nodules of C. equisetifolia were examined. The germination rate of the seeds markedly decreased as the NaCl concentration increased and germination did not occur at 300 mM NaCl. The fresh weight of both shoots and roots of the seedlings treated with NaCl for 6 weeks apparently decreased as the NaCl concentration increased. However, root nodules were formed by inoculation with the Frankia Ceq1 strain in some seedlings treated with 300 mM NaCl and the viability of the seedlings at 500 mM NaCl was almost the same as that of the seedlings not subjected to the NaCl treatment. The Na⁺ concentration in the shoots sharply increased with the elevation of the NaCl concentration in the ambient solution, but the level was approximately 300 mM even in the seedlings treated with 500 mM NaCl for 6 weeks. On the other hand, the increase of the Na⁺ concentration in the roots by the NaCl treatment was much smaller than that in the shoots and the level was less than 150 mM. The growth of the free-living Frankia Ceq1 strain was approximately linearly suppressed as the NaCl concentration in the medium increased and the hyphae became somewhat thicker and shorter or disintegrated in the medium containing NaCl at a concentration above 150 mM. The Na⁺ concentration in the cells increased as the NaCl concentration in the medium increased, but the level was maintained at less than 30 mM even in the medium containing 500 mM NaCl. The cells whose growth was suppressed by the NaCI treatment grew actively again at almost the same rate as the control cells (not subjected to the NaCl treatment) when they were transferred to NaCl-free medium. These results strongly suggested that both C. equisetifolia seedlings and Frankia Ceq1 strain are highly tolerant to salt and this symbiotic system is useful for the recovery of the vegetation in areas with severe salt accumulation.     

Increase in the abundance of cladocera at pH 5.1 in experimentally-acidified lake 223, Experimental Lakes Area,Ontario

Lake 223 in the Experimental Lakes Area, northwestern Ontario was experimentally-acidified with H₂SO₄ from 1976 to the present. Cladocerans increased in absolute and relative abundance and in total biomass when the pH of Lake 223 was lowered from 6.7 to 5.1. Comparing the cladoceran community at pH 6.7 (1974) with that at pH 5.1 (1981 to 1983), Daphnia galeata mendotae disappeared, Diaphanosoma birgei became rare, Holopedium gibberum increased in abundance and Daphnia catawba, recorded for the first time in 1980, became abundant. Bosmina longirostris became more abundant. Except for the decline in D. birgei, the changes in cladoceran species composition with acidification are consistent with known responses of these species to low pH. The increase in importance of cladocerans in 1981 to 1983 was at the expense of copepods. It was hypothesized to be caused by the decline in predation by small fish during 1981 to 1983 as acidification reduced minnow populations and inhibited reproduction in trout and sucker. The loss of the population of the invertebrate predator, the opposum shrimp, Mysis relicta, in 1979 had little effect on cladoceran biomass.     

Dynamics of Forms of Inorganic Phosphorus in Soil under Coffee Plants as a Function of Successive Annual Additions of the Nutrient

Phosphorus (P) dynamics and availability in soils are influenced by P fertilization. This paper aimed to evaluate inorganic P fractions bonded to calcium (Ca), iron (Fe), and aluminum (Al), associating them with soil mineralogy. The experiment was carried out using an acidic kaolinitic–oxidic soil, located in an irrigated area cultivated with coffee plants (Coffee arabica L.), submitted to successive annual fertilizations with triple superphosphate doses of 0, 50, 100 200, and 400 kg ha^?1 phosphorus pentoxide (P₂O₅) in randomized blocks with three replications. Phosphorus fractions were determined in soil samples collected at two depths, 0–10 and 10–20 cm, according to the methodology used by Chang and Jackson (1957 Chang, S. C. and Jackson, M. L. 1957. Fractionation of soil phosphorus. Soil Science, 84: 133–144. [Crossref] , [Google Scholar]). The inorganic P fractions presented the following sequence: P-Al > P-Fe > P-Ca. The dynamics of forms of inorganic P showed that P-Al is controlling the P bioavailability as a result of an acidic pH and a very simple and thermodynamically stable clay mineralogy, typical of very weathered and old tropical soils.     

Phosphorus Fertility Assessment of Intensively Farmed Areas of Catchments Draining to the Great Barrier Reef World Heritage Area; 1: Soil Phosphorus Status

Abstract

Australia's reef water quality protection plan has a key objective: “reduce the load of pollutants from diffuse sources in the water entering the Reef.” This article reports on a survey to assess the contemporary phosphorus (P) status of fertilized cropping soils across 21 catchments in coastal Queensland, Australia. The survey focused on surface soils from cane farms, vegetable and subtropical/tropical fruit tree sites. There were sampling depth effects on P levels in sugar and fruit tree sites (lower with depth). Importantly, 84% of 105 sugarcane sites were excessively fertile and only 3% rated low (P deficient). Some 75% of 16 vegetable sites and 38% of 8 fruit tree sites had excess ratings for extractable soil P fertility. Highest total P levels (0–10 cm) occurred in fruit tree sites, followed by vegetable and sugarcane soils. There are regional differences in P soil fertility, and the recycling of mill by‐products needs attention. Part 2 (Bloesch and Rayment 2006 Bloesch, P. M. and Rayment, G. E. 2006. “Phosphorus fertility assessment of intensively farmed areas of catchments draining to the Great Barrier Reef World Heritage Area, 2: Potential of soils to release soluble phosphorus”. In Communications in Soil Science and Plant Analysis 37 [Google Scholar]) examines the potential of these soils to release soluble P in a nutrient‐sensitive area.     

Correction and standardization of critical limit of zinc for maize (Zea mays L.) crop: Bangladesh perspective

Abstract

Critical limit (CL) determination of zinc (Zn) is very important for predicting response of maize crop to its application in soils and for the crop’s actual fertilizer requirement. This study was conducted at Bangladesh Agricultural Research Institute, Gazipur, to determine the CL of Zn for maize grown in 20 soils collected from the five Agro–Ecological Zones during January to March, and April to June of 2017. The available Zn content of soils and maize biomass were estimated utilizing the extraction method with 0.005?M diethylene triamine pentaacetic acid (DTPA). During January to March and April to June 2017, the amount of DTPA extractable Zn in different soils ranged from 0.60–3.25?mg?kg^?1 and 0.50–1.68?mg?kg^?1, respectively. During both periods of crop growth (January to March and April to June, 2017), the soil available zinc was negatively significantly correlated with soil pH, available P, exchangeable Ca, exchangeable Mg and positively significantly correlated with relative dry matter (DM) yield. Soil Zn also positively significantly correlated with maize tissue Zn content (r?=?0.521*). However, the CL of Zn were estimated to be 0.84?mg kg^?1 in soils and 26.1?mg kg^?1 in maize tissue for maize cropping as determined by Cate and Nelson’s (1965 Cate, R. B., and L. A. Nelson. 1965. A rapid method for correlation of soil test analysis with plant response data. International soil testing series technical Bulletin No. I North Caroline State University, Agricultural Experiment Statistics, Releigh, USA, pp. 135–136. [Google Scholar]) graphical procedure. Maize crop may respond to Zn application in soils containing Zn at/below the above level. This data may be used for predicting plant response to Zn fertilizer and development of crop Zn nutrition guide for maximum production.     

Mercury in plants,soil and atmosphere near a chlor-alkali complex

Data of atmospheric Hg concentrations measured near the chlor-alkali complex of Rosignano Solvay (Livorno, Italy) show that the impact of the industry on the terrestrial environment is restricted to a close area around; background values (3 to 5 ng m^?3) are reached within a radius of 4 to 5 km. Hg levels in plants (Poa sp. Pinus nigra and Solidago sp.) and in soil show the highest values in the sampling stations near the electrolytic cells.     

Analysis and use of cumulative nutrient uptake formulas in plant nutrition and the temporal-weight-averaged influx

A generalized cumulative uptake formula of nutrient uptake by roots following our previous formula (Reginato-Tarzia, Comm. Soil Sci. and Plant., 33 (2002 Reginato, J. C., and D. A. Tarzia. 2002. An alternative formula to compute the nutrient uptake for roots. Communications in Soil Science and Plant Analysis 33 (5&;6):821–30.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]), 821-830) is developed. Cumulative nutrient uptake obtained by this formula is compared with the simulated results obtained by the Claassen and Barber (Claassen and Barber, Agronomy J., 68 (1976 Claassen, N., and S. A. Barber. 1976. Simulation model for nutrient uptake from soil by a growing plant root system. Agronomy Journal 68:961–64.[Crossref], [Web of Science ®] , [Google Scholar]) 961–964) and Cushman (Cushman, Soil Sci. Soc., 43 (1979 Cushman, J. H. 1979. An analytical solution to solute transport near root surfaces for low initial concentrations: I. Equation development. Soil Science Society of America Journal 43:1087–90.[Crossref], [Web of Science ®] , [Google Scholar]) 1087–1090) formulas. A mass balance is analyzed for the three formulas of cumulative nutrient uptake in order to decide which of them is correct. Moreover, the mass balance is also verified through a computational algorithm using data obtained from literature, and we compute the potassium (K) uptake for maize for low and high soil concentrations using the three mentioned formulas. The theoretical analysis shows that Claassen and Barber, and Cushman formulas do not verify, in general, the mass balance condition. The Claassen and Barber formula only verifies this condition when the influx is constant and root grows linearly. The Cushman formula verifies the mass balance when the influx is constant regardless of the law of root growth. Reginato and Tarzia formula always verifies the mass balance whatever be the representative functions for the influx and the law of root growth. Moreover, we propose a redefinition of the averaged influx from which the Williams formula (Williams, J. Scientific Res., 1 (1948 Williams, R. F. 1948. The effect of phosphorus supply on the rates of intake of phosphorus and nitrogen upon certain aspects of phosphorus metabolism in gramineous plants. Australian Journal of Scientific Research 1:333–61. [Google Scholar]) 333–361) can be deduced. We remark that Williams formula is a consequence of our definition of temporal-weight-averaged influx for all root growth law expressions. Also, we present a comparison of influx and cumulative uptake of cadmium (Cd) with data extracted from literature. Cumulative uptake is obtained through the Barber–Cushman model and our moving boundary model by using the redefinition of averaged influx on root surface and the correct cumulative uptake formula presented in this paper.