NITROGEN SOURCE AND MANGANESE APPLICATION EFFECTS ON MANGANESE DYNAMICS IN THE RHIZOSPHERE OF WHEAT CULTIVARS GROWN ON MANGANESE-DEFICIENT SOILS

To study the effect of two different nitrogen (N) sources and manganese application on root-shoot relations and manganese (Mn) dynamics in the rhizosphere of two wheat cultivars, a screen house experiment was conducted using manganese-deficient soil. Significantly higher root length (RL), root surface area, shoot dry weight (SDW), root length density, and manganese uptake were recorded in calcium nitrate supplied plants of cultivar ‘WH 542’ when applied with calcium nitrate along with manganese rather than ammonium sulfate. Cultivar ‘PD W274’ produced 72% of the maximum RL and 77% of the maximum SDW under similar conditions. Results indicated that cultivar ‘WH 542’ was more manganese efficient than ‘PD W274’ and calcium nitrate was a better source of nitrogen than ammonium sulfate. However, maximum shoot manganese content was recorded in ammonium sulfate supplied plants, which was due to depletion of manganese at root surface to a lower value, causing higher concentration gradient and hence higher manganese influx to root.     

农业生产中的铁锰平衡问题

本文根据对菠萝和水稻的研究,论述了土壤和植物体内铁与锰的关系,认为在植物体内铁与锰的比例应保持一个平衡的关系。如果锰多铁少、比例失调,作物的正常生长将受到危害。     

IRISH PLAGGEN SOILS—THEIR DISTRIBUTION, ORIGIN, AND PROPERTIES

Soils have been described in Ireland which meet the definition of thick manmade surface horizons conforming to Plaggen epipedons (Conry, 1969). Unlike the north-west European Plaggen soils these Irish Plaggen soils have not been formed by the prolonged addition of Plaggen material (heather sods, forest litter, or grass plaggen) and dung, but were formed by the addition of calcareous sea sand, applied either alone or mixed with stable dung. Although only small quantities of grass sods were used in the formation of the Irish Plaggen soils, they should not be separated genetically from the true Plaggen soils of NW. Europe. They occur in coastal areas, within one mile of the coast approximately, where sources of calcareous sand are readily available. These Plaggen soils generally have a loamy-coarse-sand to coarse-sandy-loam texture, a granular to single grain structure and loose to very friable consistence. Colour is directly related to the colour of the original soil. Depth varies from field to field and is related to population density. The Irish Plaggen soils are always base saturated. Phosphorus, potassium, magnesium, and sodium are very much higher than in the unsanded counterpart. Trace element deficiencies include boron, magnanese, and cobalt. Like the Plaggen soils of NW. Europe the Plaggen soils in Ireland are superior in productivity to their non-Plaggen counterparts; not only has man's influence increased crop yield substantially, but the range of crops produced has also been enlarged. The Irish Plaggen soils show symptoms of a moisture deficit only in prolonged dry periods.     

AMELIORATION OF PHYTOTOXICITY OF COBALT BY HIGH PHOSPHORUS AND ITS WITHDRAWAL IN TOMATO

ABSTRACT

Tomato (Lycopersicon esculentum) cv Ali vikas was grown at normal [without added cobalt (Co)] and excess Co (0.5?mM) in refined sand to see the effects of excess Co (0.5?mM) and its amelioration by high phosphorus (P). Apart from this, effect of high P (3?mM) and its withdrawal for 45 days (after 56 days of excess P supply) have also been observed on tomato physiology. The visible symptoms of excess Co appeared first in high P but were more pronounced in adequate P. In tomato, excess Co depressed the biomass, concentration of iron (Fe), chlorophyll a and b, Hill reaction activity, and activity of catalase and increased that of peroxidase, acid phosphatase, and ribonuclease along with accumulation of Co, more significantly with adequate P. High P partially ameliorated the effects of excess Co in tomato with almost no toxic effects of its own. Complete withdrawal of high P (for 14 days) improved the biomass, content of chlorophyll a and b, and Fe, and activity of catalase and reduced Co accumulation in different parts and P fractions in leaves. This also lowered the activities of peroxidase, acid phosphatase, and ribonuclease in addition to the concentration of various carbohydrate fractions which otherwise remained accumulated in leaves of tomato at excess P/excess Co treatment.     

THE DISTRIBUTION OF IRON, MANGANESE, AND SCOTLAND ALUMINIUM IN SOME SOILS FROM NORTH-EAST SCOTLAND

Twenty-four soils from north-east Scotland have been subjected to differential extraction techniques to determine the effect of hydromorphism on various Fe, Mn, and A1 fractions. There were pronounced losses of dithionite-extractable Fe and Mn from gleyed horizons, but the 'silicate-Fe’fraction appeared to be relatively unaffected. The oxalate-extractable Fe and A1 fractions also decreased in response to gleying. The ratio of the oxalate- to dithionite-extractable Fe fractions (Fe₀/Fe_d) increased in gleyed horizons, presumably due to variations in the rate of ageing and crystallization of amorphous Fe oxides and hydroxides.     

MAGNESIUM DEFICIENCY IN CHESTNUT GROVES: THE INFLUENCE OF SOIL MANGANESE

In northeastern Portugal, it has been difficult to identify the threshold value of exchangeable magnesium (Mg) below which Mg deficiency occurs in chestnuts (Castanea sativa Mill.), since discrepancies have been observed in some areas, apparently associated with parent material. A regional survey was carried out in chestnut groves established in soils derived from bedrock of several geological formations, some of them rich in manganese (Mn). Leaf sampling and soil analysis were performed in 38 groves. The lowest value of foliar Mg concentration under good growing conditions was 1.8 g kg^?1 and the highest value in trees with Mg deficiency symptoms was 1.5 g kg^?1. Under acidic soil conditions higher levels of extractable Mn propitiate Mg deficiency. The soils need to reach higher exchangeable Mg (≥0.34 cmolc kg^?1) in order to supply Mg. For lower values of extractable Mn, the deficiency appears when exchangeable Mg is <0.20 cmolc kg^?1 of soil.     

INDUCTION OF OXIDATIVE STRESS AND ANTIOXIDANT ENZYMES BY EXCESS COBALT IN MUSTARD

This study focuses on induction of oxidative stress and antioxidative defense mechanism on exposure to excess cobalt (Co) in mustard (Brassica campestris L.; cv. ‘T-59’) plants grown in refined sand. Plants were grown for 40 days at normal (0.1 μM) Co. Additional cobalt was supplied from d 41 at 6 levels, i.e., 0.1 (control), 100, 200, 300, 400 and 500 μM as cobalt sulfate. The primary site of Co toxicity was shoots where middle leaves developed interveinal chlorosis after three days of excess cobalt supply (>100 μM). At severity these chlorotic spots became necrotic and affected areas appeared dry and papery, at this stage, growth of the plants were completely checked, the upper part of the stem became dry and hanged down. The toxicity of cobalt at d 46, i.e., six days after metal supply, (DAMS) reduced the dry weight, concentrations of chlorophyll a, b and carotenoids in leaves and tissue Fe with decreased activity of catalase and lipid peroxidation. Enhancement in proline concentration and elevated activities of antioxidant enzymes peroxidase, superoxide dismutase and ascorbate peroxidase were observed in leaves and roots in response to excess Co supply in mustard. Cobalt concentration of mustard in leaves and roots, ranged from 200 to 397 μg g^?1 at excess Co as compared to 1.1 to 2.5 μg Co g^?1 dry matter in control (0.1 μM Co).     

RELATIONSHIP OF IRON-MANGANESE TOXICITY DISORDER IN MARIGOLD TO MANGANESE AND MAGNESIUM NUTRITION

The iron-manganese (Fe-Mn) disorder in marigold (Tagetes erecta L.) is related to high Mn and low magnesium (Mg) in leaves. Three solution-culture experiments with marigold were conducted in a greenhouse. One investigated Mn and the disorder. Based on dry matter production, 4.5 mg Mn/L was the toxicity concentration and gave 880 mg Mn g^?1 dry weight in new leaves and 1200 in old leaves. Manganese above 4.5 mg L^?1 produced bronzed speckles on leaves. A second experiment investigated Mg and the disorder. Based on dry matter production, 10 mg Mg L^?1 was the deficiency concentration and gave 1.5% Mg in the shoots. Symptoms of Mg deficiency did not resemble those of the disorder. A third experiment investigated Mn and Mg. Leaf chlorosis appeared at 2.5 mg Mn L^?1 with the lowest supply of Mg. These experiments suggest that Mn supply is related to the disorder but increasing Mg does not alleviate the problem.     

IMPROVEMENT OF SCREENING FOR MANGANESE EFFICIENCY BY PRODUCING SEED WITH SIMILAR MANGANESE CONTENT IN DIFFERENT GENOTYPES AND GENETIC STOCKS

ABSTRACT

Genetic improvement of manganese efficiency of crops demands a precise bioassay that avoids the confounding effect of seed manganese on the bioassay for the trait, for a proper comparison of the genotypes the seed manganese content must be similar. Variation in seed manganese can be minimized by the addition of manganese to individual seeds to be planted providing the effect of seed manganese content on early growth and development for the chosen genotype has been determined. It was hypothesized that growing the plants as mono-culms in very small pots under subclinical manganese deficiency would limit grain yield and yield attribute among genotypes, resulting in seed with less variation in manganese content across genotypes. The effect on yield and components of soil fertility ranging from University of California (UC) potting mix, fortified with Osmocote, to 100% manganese-deficient calcareous sand from Wangary, South Australia (Psamment) was determined for 20 bread wheat genotypes and breeding lines. It was observed that a mix of 70% UC and 30% Calcareous Wangary sand from South Australia in small pots minimized variation in grain yield and its components (number of tillers, number of seeds/head, weight of seed) and also lowered variation in seed manganese content among wheat genotypes. This was confirmed in pots of 70/30 UC-sand mix for five bread wheat cultivars, Worrakatta, Barunga, Schomburg, Excalibur, and Frame. The pot results from three replicates were compared with field results for the same genotypes grown at five randomly selected wheat-growing areas in South Australia: Paskeville, Geranium, Minnipa, Nunji, and Cummins. The variation in seed manganese content across genotypes was much less in pot grown seed.

Aneuploid stocks (D-genome diosomic substitution lines) normally have highly variable seed size. Production of seed with similar manganese content was only feasible by growing the seed under multiple levels of soil manganese supply and after analysis selecting seeds with similar manganese content among the various manganese treatments. The effect of aneuploidy on seedling vigor, root growth, seed size and agronomic performance has been reported elsewhere. The effect on seed manganese content and the genetic analysis of micronutrient (manganese) efficiency were determined in the current study.     

MANGANESE TOXICITY IN THREE SPECIES OF ANNUAL MEDICS

The selection of Medicago spp. cultivars tolerant to high levels of manganese (Mn) is needed if they are to be established in acidic soils. We compared the growth of three species of annual medics (M. polymorpha, M. murex and M. tornata) in an acid soil with a high level of extractable Mn, and in nutrient solutions with 100 and 500 μM Mn. M. polymorpha accumulated the greatest biomass in the field, in pots, and in nutrient solution, but M. murex was the most tolerant of a high level of Mn in nutrient solution and in the unlimed acid soil in pots. M. tornata produced a similar biomass to M. murex in limed soil and in a nutrient solution with a low level of Mn. However, it was very sensitive to a high level of Mn, both in solution and in unlimed soil. The relative growth between the three species in the field, in pots, and in nutrient solution was comparable, suggesting that selection in nutrient solution can be used to identify ecotypes tolerant to Mn.     

MANGANESE EFFICIENCY OF WHEAT CULTIVARS AS RELATED TO ROOT GROWTH AND INTERNAL MANGANESE REQUIREMENT

ABSTRACT

Under field conditions, wheat cultivar PBW 343 produced 1.5 times higher grain yield than PDW 233, when grown on low manganese (Mn) soil. To explain the differences in Mn efficiency a pot experiment was conducted using Mn deficient Typic ustochrept loamy sand soil treated with 0, 50, and 100?mg?Mn?kg^?1 soil. In no-Mn treatment, both the wheat cultivars showed Mn deficiency symptoms and cultivar PBW 343 produced 30% of the maximum dry matter yield (DMY) attained at high Mn supply, while PDW 233 produced only 18% of its maximum DMY after 40 days of growth. With application of 50?mg?Mn?kg^?1 soil, the DMY significantly increased to 87% and 50% of the maximum for PBW 343 and PDW 233, respectively. These results indicate that aestivum cultivar PBW 343 was more Mn efficient than durum cultivar PDW 233. Manganese efficient cultivar PBW 343 had a lower internal Mn requirement than PDW 233 because at the same shoot Mn concentration PBW 343 produced more DMY. The root growth of both wheat cultivars was similar at sufficient Mn supply, the root length (RL)?:?DMY ratio being equal. At decreasing Mn supply root growth was depressed more strongly than shoot growth, the inhibition being more severe in Mn inefficient cultivar PDW 233, indicating the importance of root system size for Mn efficiency between these two wheat cultivars. A nutrient uptake model closely described Mn influx in both the cultivars, indicating that calculated concentration profiles were realistic and that chemical mobilization of Mn in the rhizosphere was not responsible for higher Mn efficiency of PBW 343. Calculated concentration profiles showed that in soil not fertilized with Mn, initial soil solution Mn concentration of 0.23?µM decreased to only 0.21?µM at the root surface after 27 days of uptake. This 7.4% decrease in Mn concentration at the root surface indicated that roots could not decrease Mn concentration to a lower value which would have caused higher transport of Mn to root surface and hence resulted in higher Mn influx.     

GROWTH AND IRON-MANGANESE RELATIONSHIPS IN DRY BEAN AS AFFECTED BY FOLIAR AND SOIL APPLICATIONS OF IRON AND MANGANESE IN A CALCAREOUS SOIL

Manganese (Mn) deficiency may be induced by adding large quantities of iron (Fe), provided that soil manganese is marginally deficient. Results of a greenhouse study showed that iron soil application did not influence shoot dry matter yield of dry bean due to the fact that the iron:manganese ratio in aerial parts of dry bean was higher than 0.4. A foliar spray of 2% iron sulfate significantly reduced it probably due to the high level of shoot iron and iron:manganese ratio greater than 4. Iron application decreased concentration/uptake of shoot manganese due to the iron-manganese antagonistic relationships. Mangenese soil application is not an effective method in correction of manganese deficiency induced by iron fertilizers. Iron did not affect root manganese uptake, indicating that manganese absorption was not affected by iron application. Both manganese/iron soil tests are recommended in calcareous soils with manganese soil test in marginal range.     

EFFECT OF BORON-DOPED GOETHITE ON SOIL ACIDITY,DIFFERENT FORMS OF MANGANESE IN RED SOIL AND THE GROWTH OF RAPE (BRASSICA NAPUS L.) SEEDLINGS

Rape (Brassica napus L.) seedling pot experiments were performed with a red soil treated with goethite which had boron (B) either adsorbed (ad-B-goethite) or occluded (oc-B-goethite). Soil acidity, different forms of manganese in the soils and different elements content of the rape seedlings were determined. It was found that the addition of boron-containing goethite to the soils resulted in increased rape growth, elevated soil pH and decreased exchangeable acidity. Compared with the control, boron-containing goethite elevated the content of exchangeable manganese (Mn) (EXC-Mn), organic matter bound Mn (OM-Mn), reducible oxide Mn (RO-Mn) and residual Mn (RES-Mn) which were difficult to use for plant. Low labile organic matter was significantly correlated with easily reducible oxide Mn (ERO-Mn) (P < 0.01) and RO-Mn (P < 0.05). Middle organic matter and soil pH was significantly (P < 0.05) correlated with RES-Mn. Stepwise regression was used to select the combination of variables that best estimates shoot and root dry weight of rape seedling. Among them, soil pH, EXC-Mn, OM-Mn, RO-Mn and RES-Mn significantly influenced the dry weight of rape seedlings. The addition of boron-containing goethite improved the uptake of iron (Fe), calcium (Ca), magnesium (Mg), and copper (Cu) element and decreased the uptake of Mn and zinc (Zn) element in rape seedling. The results suggested that boron-containing goethite could provide a better soil acidity environment for plant growth; it was also an important agent increasing a part of manganese difficult to use for plant and reducing the activity of soil manganese, which was beneficial to altering rape seedling growth.     

SOIL APPLIED COBALT AND COPPER ALTER THE RHIZOBIUM SYMBIOSIS AND GROWTH STATUS OF LABLAB PURPUREUS (L.) SWEET

A pot experiment was performed to investigate the effect of cobalt (Co) and copper (Cu) nutrition on nodulation, nodule activity and growth of Lablab purpureus plants growing in sandy clay loam soil collected from Toshka region in south of Egypt. The pots were given nutrient solution only once with addition of increasing levels of cobalt and copper (50, 100, 150 and 200 μg) as cobalt or copper sulfate solution. The present study has provided a new insight into the effect of cobalt and copper on nodulation and nodule physiology of Lablab purpureus (L.) Sweet (kashrangeeg) that has not yet been examined. Thus, the present work suggest that Co and Cu application is essential for the enhancement of nodulation, nodule activity and growth of Lablab purpureus plants growing in sandy clay loam soil deficient for theses microelements.     

THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS. VIII —A THEORY FOR THE PROPAGATION OF CHANGES OF pH IN SOILS

The way pH changes in soil are propagated by movement of acids and bases is described. In acid soils the H₃O⁺-H₂O acid-base pair is most important, while in alkaline soils the H₂CO₃-HCO₃^? pair is always dominant, its effect depending directly on the pressure of CO₂. In neutral and slightly acid soils, soluble organic matter and the H₂PO₄^?-HPO²₄^? pair may also contribute. A soil acidity diffusion coefficient is derived, and defined as: where v_l= the volume fraction of the soil solution, f_l= the impedance factor for the liquid diffusion pathway, b_HS= the pH buffer capacity of the soil, b _HB= the pH buffer capacity of each mobile acid-base pair, Dl _HB= the diffusion coefficient of each mobile acid-base pair in free solution, and the sum is taken over all mobile acid-base pairs. The soil acidity diffusion coefficient may be used to predict the course of pH equilibration in practical situations. It is high in acid and alkaline soil, and at a minimum in slightly acid soil. It is little affected by variation of the ionic strength of the soil solution at concentrations less than 0.01M. When the pH buffer capacity of the soil is constant, and only the H₃O⁺-H₂O and H₂CO₃-HCO₃^? pairs are important, the soil acidity diffusion coefficient varies as cosh{2.303(pH—pH₀)}, where pH₀ is the pH at which the soil-acidity diffusion coefficient is a minimum.