Magnesium-manganese interaction in soybean cultivars with different nutritional requirements

Manganese (Mn) deficiency in soybean has occurred mainly in soils with surface dolomite lime application, which increases pH and the magnesium (Mg) concentration in the surface layer. The objective of this study was to investigate the influence of Mg on the Mn uptake in four soybean cultivars with different nutritional requirements. The experiment was conducted under greenhouse conditions in a completely randomized design, in 4 × 2 × 4 factorial scheme [four soybean cultivars, two Mg rates (0.1 and 1.0 mmol L^?1) and four Mn rates (0.0, 1.0, 2.0, and 5.0 µmol L^?1)], with four replicates. The cultivars used in the experiment were: IAC 17 and FT Estrela (for soils fertility or high nutritional demand) and IAC 15–1 and DM Nobre (for soils partially corrected or medium nutritional demand). The root dry weight (RDW), shoot dry weight (SDW), SDW/RDW ratio, chlorophyll content, seed yield and foliar concentrations of nitrogen (N), phosphorus (P), potassium (K), Mg, calcium (Ca), iron (Fe), Mn, and zinc (Zn) were determined. The application of the highest Mg rate increased seed yield. This was also observed with a Mn rate up to 3.0 μmol L^?1. There was an interaction of Mg and Mn in the plant, and it was found that the IAC 17 cultivar was the most sensitive to Mn, while FT Estrela had the lowest performance. N, P, K, and Zn concentrations were significantly influenced by Mn rates. The Mg and Mn rates had a significant effect on Mg foliar concentrations. The rate of 1.0 mmol L^?1 of Mg provided the lowest levels of nutrients to the plant and increased SDW and seed yield, regardless of the nutritional requirement of each cultivar.     

ALLEVIATION OF CADMIUM-TOXICITY BY APPLICATION OF ZINC AND ASCORBIC ACID IN BARLEY

ABSTRACT

Effect of cadmium (Cd) on biomass accumulation and physiological activity and alleviation of Cd-toxicity by application of zinc (Zn) and ascorbic acid in barley was studied, using semisolid medium culture including 15 treatments [four Cd concentration treatments: 0.1, 1, 5, 50?µmol?L^?1, four treatments with addition of 300?µmol?L^?1 Zn or 250?mg?L^?1 ascorbic acid (ASA) based on these four Cd concentrations, respectively, and three controls: basic nutrient medium, and with Zn or ASA, respectively]. Cadmium addition to semisolid medium, at a concentration of 1, 5, and 50?µmol?L^?1, inhibited biomass accumulation and increased malondialdehyde (MDA) content of barley plants, while the addition of 0.1?µmol?L^?1 Cd increased slightly dry mass. There was a tendency to a decrease in Zn, copper (Cu) concentrations both in shoots and roots and iron (Fe) in shoots of barley plants exposed to 1 to 50?µmol?L^?1 Cd. In addition, there were indications of a stress repose characterized by increased superoxide dismutase (SOD) and peroxidase (POD) activities relative to plants not subjected to Cd. The physiological changes caused by Cd toxicity could be alleviated to different extent by application of 300?µmol?L^?1 Zn or 250?mg?L^?1 ASA in Cd stressed plants. The most pronounced effects of adding Zn or ASA in Cd stressed medium were expressed in the decreased MDA and increased biomass accumulation, e.g., MDA contents were reduced (p≤0.01) by 4.8%–17.8% in shoots and 0.5%–19.7% in roots by adding 300?µmol?L^?1 Zn, in 50?µmol?L^?1 Cd stressed plants, and by 1.3%–7.4% in shoots and 2.6%–4.5% in roots by application of 250?µmol?L^?1 ASA, respectively. However, ASA addition may enhance Cd translation from root to shoot, accordingly, ASA would be unsuitable for the edible crops grown in Cd contaminated soils to alleviate phytotoxicity of Cd.     

Surface Liming and Zinc Availability in a Long‐Term Experiment under No‐Till System

No‐till (NT) system with crop rotation is one of the most effective strategies to improve agricultural sustainability in tropical and subtropical regions. To control soil acidity in NT, lime is broadcast on the surface without incorporation. The increase in soil pH due to surface liming may decrease zinc (Zn) availability and its uptake by crops. A field experiment was performed in Paraná State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate Zn bioavailability in a NT system after surface liming and re‐liming. Dolomitic lime was surface applied on the main plots in July 1993 at the rates of 0, 2, 4, and 6 Mg ha^?1. In June 2000, the main plots were divided in two subplots to study of the effect of surface re‐liming at the rates of 0 and 3 Mg ha^?1. The cropping sequence was soybean [Glycine max (L.) Merrill] (2001–2 and 2002–3), wheat (Triticum aestivum L.) (2003), soybean (2003–4), corn (Zea mays L.) (2004–5), and soybean (2005–6). Soil samples were collected at the following depths: 0–0.05, 0.05–0.10, and 0.10–0.20 m, 10 years after surface liming and 3 years after surface re‐liming. Soil Zn levels were extracted by four extractants: (i) 0.005 mol L^?1 diethylenetriaminepentaacetic acid (DTPA) + 0.1 mol L^?1 triethanolamine (TEA) + 0.01 mol L^?1 calcium chloride (CaCl₂) solution at pH 7.3 (DTPA–TEA), (ii) 0.1 mol L^?1 hydrochloric acid (HCl) solution, (iii) Mehlich 1 solution, and (iv) Mehlich 3 solution. Zinc concentrations in leaves and grains of soybean, wheat, and corn were also determined. Soil pH (0.01 mol L^?1 CaCl₂ suspension) varied from 4.4 to 6.1, at the 0‐ to 0.05‐m depth, from 4.2 to 5.3 at the 0.05‐ to 0.10‐m depth, and from 4.2 to 4.8 at the 0.10‐ to 0.20‐m depth, after liming and re‐liming. Zinc concentrations evaluated by DTPA–TEA, 0.1 mol L^?1 HCl, Mehlich 1, and Mehlich 3 solutions were not changed as a result of lime rate application. Re‐liming increased Zn concentrations extracted by 0.1 mol L^?1 HCl at 0–0.05 m deep and by DTPA–TEA at 0.05–0.10 m deep. Surface‐applied lime promoted a decrease in Zn concentrations of the crops, mainly in grains, because of increased soil pH at the surface layers. Regardless of the liming treatments, levels of Zn were sufficient to soybean, wheat, and corn nutrition under NT.     

Zinc and amino acids on wheat-soybean intercropping under no-till management

Abstract

Foliar fertilization with micronutrients and amino acids (AAs) has been used to increase the grain yield and quality of different crops. The aim of the present study was to evaluate the effects of Zn and AAs foliar application on physiological parameters, nutritional status, yield components and grain yield of wheat-soybean intercropping under a no-till management. We used a randomized block experimental design consisting of eight treatments and four replicates. The treatments were five Zn rates (0, 1, 2, 4 and 8?kg ha^?1) and 2?L ha^?1 of AAs and three additional treatments: a control (without the Zn or AA application), 2?kg ha^?1 Zn and 2?kg ha^?1 Zn + 1?L AA. The treatments were applied by spraying during the final elongation stage and at the beginning of pre-earing for the wheat and in growth stage V6 for the soybean for two crop years in a Typic Oxisol (860?g kg^?1 clay). Zinc foliar fertilization increased the wheat grain Zn concentrations. The Zn rates and AA foliar fertilization in soil with did not affect the physiological parameters, nutrient status or yield components. The AA application at the different concentrations tested changed the soybean grain yield and the leaf N concentration. The results suggest that Zn and amino acids application increases the grains Zn concentration in the wheat, being an important strategy to agronomic biofortification.     

Zinc Nutrition of Onion: Proposed Diagnostic Criteria

ABSTRACT

Zinc (Zn) deficiency is a global nutritional problem in crops grown in calcareous soils. However, plant analysis criteria, a good tool for interpreting crop Zn requirement, is scarcely reported in literature for onion (Allium cepa L.). In a greenhouse experiment, Zn requirement, critical concentrations in diagnostic parts and genotypic variation were assessed using four onion cultivars (‘Swat-1’, ‘Phulkara,’ ‘Sariab Red,’ and ‘Chilton-89’) grown in a Zn-deficient (AB-DTPA extractable, 0.44 Zn mg kg^?1), calcareous soil of Gujranwala series (Typic Hapludalf). Five rates of Zn, ranging from 0 to 16 mg Zn kg^?1 soil, were applied as zinc sulphate (ZnSO₄·7H₂O) along with adequate basal fertilization of nitrogen (N), phosphorus (P), potassium (K), and boron (B). Four onion seedlings were transplanted in each pot. Whole shoots of two plants and recently matured leaves of other two plants were sampled. Zinc application significantly increased dry bulb yield and maximum yield was produced with 8 mg Zn kg^?1. Application of higher rates did not improve yield further. The cultivars differed significantly in Zn efficiency and cv. ‘Swat-1’ was most Zn-efficient. Fertilizer requirement for near-maximum dry bulb yield was 2.5 mg Zn kg^?1. Plant tissue critical Zn concentrations were 30 mg kg^?1 in young whole shoots, 25 mg kg^?1 in matured leaves, 16 mg kg^?1 in tops and 14 mg Zn kg^?1 in bulb. Zinc content in mature bulb also appeared to be a good indicator of soil Zn availability status.     

Quantity–Intensity Relationships of Potassium in Soils under Some Guava Orchards on Marginal Lands

Quantity–intensity relations of potassium (K) were worked out for guava orchard soils. Equilibrium activity ratio of potassium (AR_e ^k) ranged from 0.46?×?10^?3 to 21.30?×?10^?3 (mol L^?1)^0.5. The majority of the samples had less than 1?×?10^?3 (mol L^?1)^0.5, indicating K depletion in these soils due to continuous K mining. AR_e ^k was significantly and positively correlated with available forms of K, K saturation percentage, labile K (K_L), and specific-site K (K_X) and negatively correlated with free energy of exchange (–ΔG). The potential buffering capacity (PBC₀ ^K) of K varied from 8.8 to 286.2 cmol kg^?1/(mol L^?1)^0.5. PBC₀ ^K was positively and significantly correlated with clay content. Sixty percent of the soils had ΔK⁰ values of less than 0.1 cmol kg^?1. High K_G (Gapon selectivity coefficent) indicated high affinity for K in these soils. Leaf K was positively and significantly correlated with ΔK⁰, K_L, and K_X and negatively correlated with –ΔG.     

Growth characteristics,phytate contents,and coagulation properties of soymilk from a low-phytate Japanese soybean (Glycine max (L.) Merr.) line

The phytic acid (myo-inositol hexakisphosphate or InsP₆) content of seed crops is important to their nutritional quality. Since it represents 75?±?10% of the total seed phosphorus (P), phytic acid is also important regarding the management of P in agricultural production. A low-phytate F5 line, No. T-2-250-4-20, was selected from the progeny of a cross between the low-phytate soybean line CX1834 and the Japanese commercial cultivar Tanbakuro. This line and its parents were grown in a field nursery, and the growth characteristics, phytate accumulation, and processing suitability for tofu were evaluated. At full maturity, the weight of seeds per plant of line T-2-250-4-20 was 5.2- and 1.3-fold higher than that of CX1834 and Tanbakuro, respectively. The amount of phytate-phosphorus as a percentage of the total P content in seeds was 23% in line T-2-250-4-20-34, 30% in CX1834, and 69% in Tanbakuro. No significant difference was observed among the three cultivars/lines in their seed magnesium (Mg), potassium (K), crude protein, and sugar. However, the calcium (Ca), crude fat and ash contents in seeds of line T-2-250-4-20-34 and Tanbakuro was lowered compared to that of CX1834. The breaking stress of tofu was estimated employing a rheometer with a decreasing concentration of the coagulant magnesium chloride (MgCl₂), starting at 15.7?mmol?L^?1. In tofu made from Tanbakuro, the concentration of MgCl₂ required to achieve the maximum breaking stress was 12.6?mmol?L^?1; however, it was 9.5?mmol?L^?1 for tofu made from T-2-250-4-20-34 and CX1834. The tofu made from Tanbakuro was soft and broke at 6.3?mmol?L^?1 MgCl₂, but, in line T-2-250-4-20-34, harder tofu was made with lower MgCl₂ concentrations. No difference was observed among the cultivars/lines in the SDS-PAGE patterns of protein in soymilk. These results indicate that we have developed a low-phytate soybean with adequate productivity, and confirmed that tofu made from the low-phytate T-2-250-4-20-34 soybean becomes coagulated and harder at a lower MgCl₂ concentration than that from high-phytate soybean cultivars.     

Interaction of Glyphosate with Zinc for the Yield,Photosynthesis, Soil Fertility and Nutritional Status of Soybean

Application of glyphosate herbicide in genetically modified (GM) soybean [Glycine max (L.) Merrill] in soils with low zinc (Zn) concentration may interfere in the uptake of this and other nutrients, with negative impact on productivity. Thus, an experiment was conducted in greenhouse conditions on Ustoxix Quatzipsamment soil to investigate the effects of the interaction of glyphosate with Zn for the yield, photosynthesis, soil fertility and nutritional status of soybean. The treatments consisted of two soybean varieties [BRS 133 (conventional—NGM) and its essentially derived transgenic line BRS 245RR (GM) with and without glyphosate application] and five Zn rates (0, 5, 10, 20 and 40 mg kg^?1, source zinc sulfate (ZnSO₄)), with four replicates. Except for the copper (Cu) and iron (Fe) concentrations, the introduction of the herbicide-resistant gene is the predominant factor reducing nutrient uptake, photosynthetic (A) rate, stomatal conductance (Gs), leaf chlorophyll and ureide concentrations. The administration of Zn rates lowered the leaf phosphorus (P) concentration, and there was significant increase in Zn concentration in the soil and in the plant. Except for the 20 mg kg^?1 of Zn rate, the use of the herbicide did not affect the shoot dry weight (SDW) and seed yield, and on average, the maximum seed yield was obtained with Zn concentrations of 26.4 and 18.7 mg kg^?1 extracted by Mehlich 1 and diethylenetriaminepentaacetic acid-triethanolamine (DTPA-TEA), respectively.     

Distribution of Zinc Fractions in Some Major Soils of India and the Impact on Nutrition of Rice

Abstract

Speciation study of microelements in soils is useful to assess their retention and release by the soil to the plant. Laboratory and greenhouse investigations were conducted for five soils of different agro‐ecological zones (viz., Bhuna, Delhi, Cooch‐Behar, Gurgaon, and Pabra) with diverse physicochemical properties to study the distribution of zinc (Zn) among the soil fractions with respect to the availability of Zn species for uptake by rice plant. A sequential extraction procedure was used that fractionated total soil Zn into water‐soluble (WS), exchangeable (EX), specifically adsorbed (SA), acid‐soluble (AS), manganese (Mn)‐oxide‐occluded (Mn‐OX), organic‐matter‐occluded (OM), amorphous iron (Fe)‐oxide‐bound (AFe‐OX), crystalline Fe‐oxide‐bound (CFe‐OX), and residual (RES) forms. There was a wide variation in the magnitude of these fractions among the soils. The studies revealed that more than 90% of the total Zn content occurred in the relatively inactive clay lattice and other mineral‐bound form (RES) and that only a small fraction occurred in the forms of WS, EX, OM, AFe‐OX, and CFe‐OX. Rice (Oryza sativa L.) cultivars differ widely in their sensitivity to Zn deficiency. Results suggested that Zn in water‐soluble, organic complexes, exchange positions, and amorphous sesquioxides were the fractions (pools) that played a key role in the uptake of Zn by the rice varieties (viz., Pusa‐933‐87‐1‐11‐88‐1‐2‐1, Pusa‐44, Pusa‐834, Jaya, and Pusa‐677). Isotopic ally exchangeable Zn (labile Zn) was recorded higher in Typic Ustrochrept of Pabra soil, and uptake of Zn by rice cultivars was also higher in this soil. The kinetic parameters such as maximum influx at high concentrations (I_max) and nutrient concentration in solution where influx is one half of I_max (K_m) behaved differentially with respect to varieties. The highest I_max value recorded was 9.2×10^?7 µmol cm^?2 s^?1 at the 5 mg kg^?1 Zn rate for Pusa‐933‐87‐1‐11‐88‐1‐2‐1, and the same was lowest for Pusa‐44, being 4.6×10^?7 µmol cm^?2 s^?1 at the 5 mg kg^?1 Zn rate. The K_m value was highest for Pusa‐44 (2.1×10^?4µmol cm^?2 s^?1) and lowest for Pusa‐933‐87‐1‐11‐88‐1‐2‐1 (1.20×10^?4µmol cm^?2 s^?1). The availability of Zn to rice cultivars in Typic Ustrochrepts of Bhuna and Delhi soils, which are characterized by higher activation energy and entropy factor, was accompanied by breakage of bonds or by significant structural changes.     

Variations in concentrations of N and P forms in leachates from dried soils rewetted at different rates

The rate at which dried soils are rewetted can affect the quantities and forms of nutrients in leachates. Both dried and moist replicated (n?=?3) samples of two contrasting grassland soil types (clayey vs brown earth) were irrigated during laboratory experiments with identical total amounts of water, but at different rates, ranging from 0 h, increasing by 30-min increments up to 4 h, and additionally a 24-h rewetting rate. Total P concentrations in leachates from dried samples of both soils generally decreased as rewetting rate increased, ranging from 2,923?±?589 μg P L^?1 (0.5 h rewetting rate) to 731?±?46.0 μg P L^?1 (24 h, clayey soil) and 1,588?±?45.1 μg P L^?1 (0.5 h) to 439?±?25.5 μg P L^?1 (24 h brown earth). Similar patterns in concentrations occurred for molybdate reactive P (MRP), although concentrations were generally an order of magnitude lower, indicating that the majority of the leached P was probably organic. The moist brown earth leached relatively high concentrations of MRP (maximum 232?±?10.6 μg P L^?1, 0.5 h), unlike the moist clayey soil (maximum 20.4?±?10.0 μg P L^?1, 0 h). The total oxidised N concentrations in leachates were less affected by rewetting rate, although longer rewetting rates resulted in decreased concentrations in leachates from the dried samples of both soils. The difference in responses to rewetting rates of the two soils is probably due to differences in the fate of the microbial biomass and adsorption properties in the soils. Results show that soil moisture could be an important factor in regulating nutrient losses and availability, especially under changing patterns of rainfall predicted by future climate change scenarios.     

Bioavailability of zinc and lead from a contaminated soil amended with pine bark-goat manure compost

The distribution in soil and plant uptake of zinc (Zn) and lead (Pb) as influenced by pine bark-goat manure (PBG) compost additions were investigated from the soils artificially contaminated with Zn or Pb ions using maize (Zea mays L.) as a test crop. Soils were amended with four rates of pine bark-goat manure compost (0, 50, 100, and 200 tons ha^?1) and four rates (0, 300, 600 and 1200 mg kg^?1) of Zn or Pb. Maize was planted and grown for 42 days. At harvest, plants samples were analyzed for Zn and Pb concentration. Soils samples were analyzed for pH, extractable and diethylene triamine pentaacetic acid (DTPA) extractable Zn and Pb. Extractable Zn and Pb was lower in PBG compost amended soils than in unamended soils and steadily declined with increasing amount of compost applied. The extractable fraction for Zn dropped by 62.2, 65.0 and 44.6% for 300, 600 and 1200 mg Zn kg^?1, respectively when 200 t ha^?1 of PBG compost was applied. Metal uptake by maize plants were directly related to the rate of applied heavy metal ions with greater concentrations of metals ions found where metal ions were added to non-amended soils.     

AVAILABILITY OF POTASSIUM TO RYEGRASS FROM SCOTTISH SOILS II. UPTAKE OF INITIALLY NON-EXCHANGEABLE POTASSIUM

The stable desorption parts of soil Quantity/Intensity isotherms were used to determine the contributions of initially exchangeable and non-exchangeable potassium to plant uptake from ten soils. The activity ratio, AR^K= a_K/√^aC_a, Mg at which K was first taken up from non-exchangeable sources varied from 3 × 10^?3 to 8 × 10^?3 M^1/2 depending on the soil. Uptake rates of two categories of initially non-exchangeable K were linearly related to √times;. The first category appeared to be close to equilibrium with the initially exchangeable K, and gave effective diffusion coefficients of 10^?7 cm² s^?1 for four soils. The second category gave diffusion coefficients from 10^?20 to 10^?22 cm² s^?1, probably came from internal surfaces of micaceous clays, and began to be released at activity ratios below 3 × 10^?4 to 6 × 10^?4 M^1/2 depending on soil type. The soils fell into three groups, broadly consistent with soil series, on their ability to release the second category of potassium.     

Zinc deficiency alters soybean susceptibility to pathogens and pests

Inadequate plant nutrition and biotic stress are key threats to current and future crop yields. Zinc (Zn) deficiency and toxicity in major crop plants have been documented, but there is limited information on how pathogen and pest damage may be affected by differing plant Zn levels. In our study, we used soybean plants as a host, a soybean pest, and three soybean pathogens to determine whether plant Zn levels change pest and disease assessments. Two soybean cultivars were grown in sand culture with a soluble nutrient solution that ranged from Zn‐deficient to toxic. Detached leaves from these plants were either inoculated with Aphis glycines, the soybean aphid, Xanthomonas axonopodis pv. glycines, a bacterium that causes bacterial pustule, Sclerotinia sclerotiorum, the necrotrophic fungus responsible for stem rot, or Phakopsora pachyrhizi, a biotrophic obligate pathogen that causes soybean rust. There were significant (P < 5%) effects on aphid colonization, positive counts for bacterial pustule, S. sclerotiorum leaf area affected, and numbers of rust lesions associated with the Zn treatments. Plants grown with the physiologically optimal levels of Zn (2 µM) had less (P < 5%) soybean aphids cm^?2 leaflet than plants grown without Zn, at 0.1× Zn (0.2 µM), or at 100× Zn fertilization (200 µM). Plants grown with the normal fertilization of Zn or 100× Zn had fewer (P < 5%) positive counts for bacterial pustule and less lesion area affected by S. sclerotiorum than plants grown without Zn or fertilized with 0.1× Zn. For soybean rust, plants grown with the physiologically optimal fertilization of Zn or 100× Zn had higher (P < 5%) lesions cm^?2 on leaflets from plants grown without Zn or fertilized with 0.1× Zn. These results indicate different Zn nutrition levels in soybean significantly affected aphid and disease development.     

Optimum N and P rates for greenhouse production of vegetative coleus using constant liquid feed

Many new coleus (C. hybridus cv.) cultivars are vegetatively propagated and require different fertilization practices from seed propagated cultivars. Two experiments were conducted to evaluate growth responses of Henna, Indian Summer, Mint Mocha, New Orleans Red, Red Head, and Trusty Rusty to 0, 70, 140, 280 and 420 mg·L^?1 nitrogen (N), and Henna, Mint Mocha, Red Head, and Trusty Rusty to 0, 6.2, 12.4, 24.8, or 49.6 mg·L^?1 phosphorus (P) to determine optimum constant liquid feed rates to produce marketable size plants from rooted cuttings. Positive growth responses in terms of biomass were found with increasing N rates but not P rates. For medium-sized cultivars such as Henna, Indian Summer, and New Orleans Red, quadratic responses were found in aboveground biomass, and N at 280 mg·L^?1 resulted in similar plant size and dry weight as those fertilized at 140 and 420 mg·L^?1 N. For large-sized cultivars such as Mint Mocha, Red Head and Trusty Rusty, plant dry weight responded linearly within the N range tested and were greatest at 420 mg·L^?1. However, plant visual quality was negatively affected by N rates at 280 and 420 mg·L^?1 in that, leaf color became less intense at these high N rates. Plants fertilized at 70 mg·L^?1 were smaller than those fertilized at 140 mg·L^?1, however, they received similar visual quality ratings because of more intense leaf color. Therefore, N at 70 to 140 mg·L^?1 can be used to grow most vegetative coleus for similar marketable quality. Mint Mocha and Henna were the only cultivars responded to P treatments that, 12.4 mg·L^?1 P rate resulted in greater biomass than the no-P control. All other cultivars had no response to supplemental P except a linear response in tissue P%. Therefore, supplemental P is not required during the 8 week production period when there is an initial P charge in the substrate. We found that substrate pH decreases with higher P rates, therefore supplemental P fertilizer can be used for adjusting pH. Both N and P rates found optimum in this study are lower than current industry practices (N at 150 to 250 mg·L^?1 and P at 24 mg·L^?1) and can significantly lower production cost and potential leaching of excessive nutrient into waterway. Nutrient treatments in further study on postharvest performance of vegetative coleus will be selected based on this study.     

Ratios of Nutrients in Lowland Rice Grown on Two Iron Toxic Soils in Nigeria

ABSTRACT

Iron (Fe) toxicity is a widespread nutritional soil constraint affecting rice production in the wetland soils of West Africa. Critical levels of total iron in plant causing toxicity is difficult to determine as different rice cultivars respond to excessive Fe^{2 +} in various ways in what is called “bronzing” or “yellowing” symptoms (VBS). An investigation was conducted to evaluate the relationship between plant growth and nutrient ratios at four iron levels (1000, 3000, 4000 μ g L^?1) and control. This involved two rice cultivars (‘ITA 212’ and ‘Suakoko 8’), and two soil types (Aeric Fluvaquent and Aeric Tropaquept). The experimental design was a 2 × 2 × 4 factorial in a completely randomized fashion with four replications. The results showed that nutrient ratios [phosphorus (P)/Fe, potassium (K)/Fe, calcium (Ca)/Fe, magnesium (Mg)/Fe, and manganese (Mn)/Fe), Fe content, and Fe uptake vary widely with the iron levels as well as with the age of the cultivars. The iron toxicity scores expressed as VBS increased with increasing Fe^{2 +} in the soils, resulting in simultaneous reduction of the following variables: plant height, tiller numbers/pot, relationships grain yield (GY) and dry matter yield (DMY). There were no significant difference between nutrient ratios, Fe contents, Fe uptake, the GY and DMY of both rice cultivars on both soil types. Multiple stepwise regression analysis showed that Fe uptake and Fe contents contributed 42% and 17% respectively to the variation in the grain yield of ‘ITA 212’ on Aeric Tropaquept. On both soil types and cultivars, Fe uptake and Fe content contributed between 26 and 68% to the variation in the DMY, while the nutrient ratios (P/Fe, K/Fe, Ca/Fe, and Mn/Fe) contributed between 3% and 13% DMY. Thus, it could be concluded that iron toxicity in rice is more a function of a single nutrient (Fe) rather than nutrient ratios.     

Zinc Diffusion and Self-Diffusion Coefficient in Alkaline Soils as Affected by Soil Properties and Zinc Carrier

The apparent diffusion coefficients, D_p/b+ø, of Zn and ZnEDTA were linear functions of added Zn, and were related to the adsorption and fixation capacities of soils rather than their pH. Lower apparent diffusion coefficient values were found in an Haplustoll soil that had higher clay and humus contents inspite of its lower pH. At comparable rates of added Zn, the apparent diffusion of ZnEDTA was 930–1010 (Bakyria), 700–1330 (Dirab), and 730–1880 (Baha) times that of Zn in the soils. The adsorbed Zn per cm³ of soil/Zn per cm³ of the equilibrium solution at the water content existing in the diffusion experiment approximated the capacity factor and was determined by extrapolation. The self-diffusion coefficient of Zn in Baha soil (5 × 10^?7 cm²sec^?1) of higher clay and water content was higher than in Bakyria or Dirab soil (2 × 10^?7 cm²sec^?1). These values were similar to the self-diffusion coefficient of P in soils of similar texture at similar water content.     

Variability on Yield,Nutritional Status,Soil Fertility,and Potassium-Use Efficiency by Soybean Cultivar in Acidic Soil

The use of cultivar with nutrient-use efficiency is an important strategy in the management of plant nutritional status, particularly potassium (K), because its high demand and the progressive impoverishment caused by the use of inadequate amounts cause frequent deficiency symptoms observed in soybean [Glycine max (L.) Merrill] crops. This study was conducted in greenhouse conditions in a completely randomized design with four replicates in an Typic Quartzipsamment soil aimed to assess the effect of applying two rates of K (50 and 200 mg kg^?1) on growth, shoot dry weight yield (SDWY) and seed yield (SY), nutritional status, yield components, and efficiency of K use in eleven cultivars of different characteristics and growth habits. The SDWY, SY, number of seeds per pod, number of pods, and estimated 100-seed weight showed significant interaction between cultivar and the K rates, with greater values at the rate 200 mg K kg^?1. Similarly, the concentration of nitrogen (N), phosphorus (P), K, calcium (Ca), magnesium (Mg), sulfur (S), boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) in leaves and grains varied according to the K rates and in the cultivar. The most K-use efficient cultivars were BMX Magna RR, BRS 232, BRS 284, BRS 294RR, NA 5909RR, and Vmax RR, whereas FTS Campo Mourão RR was inefficient. Regarding response to fertilization, the cultivars Vmax RR, BMX Magna RR, NA 5909RR, BRS 284, and BRS 294RR were found to be efficient and responsive, whereas the cultivar FTS Campo Mourão RR, BRS 232, BMX Potência RR, BRS 295RR, TMG 1066RR, and TMG 1067RR are inefficient and responsive to K application in the soil.     

Determination of Water-Soluble and Acid-Soluble Zinc in Soils by Flame Atomic Absorption Spectrometry after Cloud Point Extraction

A cloud point extraction (CPE) procedure has been developed for the determination of water-soluble and acid-soluble zinc (Zn) in soils by flame atomic absorption spectrometry. Deionized water and 0.1 mol L^–1 hydrochloric acid (HCl) were selected as extracting agents. In the proposed approach, 2-(5-bromo-2-pyridylazo)-5-diethylam-inophenol (5-Br-PADAP) was used as a chelating agent, and polyethylene glycol octyl phenyl ether (OP) was selected as the surfactant. Some factors including the pH of analytical solution, concentrations of the chelating agent and surfactant, equilibration temperature and time, and salt effect, which would affect the extraction efficiency and subsequent determination of Zn, were studied and optimized. Under the optimized conditions, the calibration graph was linear in the range of 5.0?×?10^–3 to 0.5 μg mL^–1, and preconcentration of 20 mL sample solution gave an enhancement factor of 25. The detection limit was 4.93?×?10^–3 μg mL^–1. Recoveries in the range of 95.0–110% were obtained. Some metal ions including iron (Fe²⁺), cobalt (Co²⁺), and manganese (Mn²⁺) would interfere with the determination of Zn. The interference from these ions can be eliminated using thiourea (0.5% w/v) and triethanolamine (0.5% w/v) as masking agents. The proposed method was applied to the determination of water-soluble and acid-soluble Zn in soils, which were collected from the suburbs of Zhengzhou, and satisfactory results were obtained. To have more understanding of the soils, we determined the total content of Zn in soils. The results showed that the water-soluble and acid-soluble Zn contents in different soils are not correlated with the total content. For example, the total content of Zn for the soil from a farm in north loop was very low, but the percentage of water-soluble Zn was very high.     

Effect of Glyphosate and Zinc Application on Yield,Soil Fertility,Yield Components,and Nutritional Status of Soybean

Glyphosate is a widely used nonselective herbicide for the control of agricultural weeds. It is being increasingly used in glyphosate resistant genetically modified plants. However, there are few studies on its effects on the nutritional status of soybean, particularly on the uptake of zinc (Zn). Two experiments were conducted under field conditions in a Typic Quartzipsamment and an Orthic Ferralsol to investigate the effect of glyphosate application × Zn interaction on soil fertility, yield components, seed yield (SY), shoot dry weight (SDW) yield, and nutritional status of soybean. The five Zn rates 0, 3, 6, 9, and 12 kg ha^?1 were used in two soybean varieties [BRS 133 (conventional—NGM) and its essentially derived transgenic line BRS 245RR (GM), which was divided into: with (+Gly) and without (–Gly) glyphosate application. Only the P (phosphorus) and Zn available concentrations in the soil were impacted by Zn rates. However, the available P concentration only decreased in the soil planted with GM soybean. Mehlich 1 and diethylenetriaminepenta acetic acid–triethanolamine (DTPA–TEA), 7.3 extractants were effective to determine the available Zn. In the two crop sites, the number of pods per plant (NPP) and the SDW yield were affected by the interaction varieties × Zn. SY was influenced by the application of the herbicide, reducing a potential phytotoxic effect with the use of high rates. Regarding the nutrients, only the foliar calcium (Ca), boron (B), iron (Fe), and manganese (Mn) concentrations were negatively affected by glyphosate, and in the case of Zn, the difference occurred only between the varieties BRS 133 and BRS 245RR.     

Zinc accumulation in lettuce cultivars grown with organic or chemical based nutritional regimes

This study determined the potential to increase Zn density of lettuce (Lactuca sativa L.) through cultivar selection and nutrient management. Organic fertilizer and Hoagland and Arnon no.1 solution factored with three zinc (Zn) levels provided as zinc sulfate (ZnSO₄) were the fertilizer regimes in a greenhouse experiment. Modern cultivars had a 32% higher fresh head weight than heritage cultivars, but each accumulated the same Zn concentration (65 mg kg^?1 dry wt). Butterhead phenotypes had a 38% lower yield than loose-leaf and had the highest Zn concentration (78 mg kg^?1 dry wt) followed by romaine (66 mg kg^?1 dry wt) and loose-leaf (53 mg kg^?1 dry wt). Concentration of Zn did not differ between fertility regimes, being about 66 mg kg^?1 dry wt with each regime. Differences in Zn concentrations were significant among individual cultivars with ranges from 42 mg g^?1 dry wt to 91 mg kg^?1 dry wt. ‘Tom Thumb’, ‘Adriana’, ‘Claremont’, and ‘Focea’ were the top in cultivar ranking, with mean Zn concentration of 63 mg kg^?1 dry wt. The results signify that selection of cultivars may be utilized to increase Zn accumulation in lettuce but that nutritional regimes had little effect on accumulation.