短链聚磷酸磷肥对土壤无机磷转化及铁锰锌有效性的影响

明确聚磷酸形态磷在土壤中的转化及其对土壤磷有效性的影响是聚磷酸类磷肥合理施用的前提.本研究通过盆栽试验比较了施用磷酸一铵和聚磷酸类磷肥对石灰性土壤和酸性红壤有效磷、无机磷转化和土壤微量元素活化的影响,同时研究了不同磷源在油菜上的施用效果.结果表明: 聚磷酸磷肥可显著提高石灰性土壤磷的有效性.与磷酸一铵(MAP)处理相比,聚磷酸处理的土壤水溶性磷和有效磷平均含量分别提高了19.0%和25.4%;对土壤无机磷连续浸提试验表明,Resin-P(树脂磷)和NaHCO₃-P(高活性磷)较MAP处理分别提高了22.8%和43.3%,NaOH-P(中活性磷)较MAP处理提高了33.8%,说明聚磷酸磷肥可显著减少石灰性土壤对磷的固定.在酸性红壤上,施用聚磷酸类磷肥对提高土壤磷的有效性及减少磷的固定效果不明显.聚磷酸磷肥可显著提高石灰性和酸性土壤Fe、Mn、Zn的有效性.与MAP处理相比,聚磷酸肥料处理下石灰性土壤有效Fe、Mn、Zn分别提高了2.1%、16.2%和20.8%,红壤的有效Fe、Mn、Zn含量分别高了6.6%、11.9%和9.2%.聚磷酸磷肥显著提高了石灰性土壤上油菜干物质、吸磷量和磷肥利用率,但在酸性红壤上聚磷酸磷肥处理肥料效应却低于MAP处理.总之,聚磷酸磷肥在提高石灰性土壤中磷的有效性、减少磷的固定、活化Fe、Mn、Zn等微量元素以及改善油菜磷素营养方面均具有显著效果,是在石灰性土壤上能有效替代正磷酸磷肥的新型磷肥.     

Effect of salinity,alkalinity and iron application on the availability of iron,manganese, phosphorus and sodium in pea (Pisum sativum L.) crop

Summary The effect of the salinity, alkalinity and Fe application on the dry matter yield and availability of Fe, Mn, P and Na were studied in the greenhouse on pea (Pisum sativum L.) crop. The highest dry matter yield was recorded in normal soil which decreased with the increase in the salinity and alkalinity, minimum being at 40 ESP. Alkalinity was more harmful to pea crop than salinity.Fe at 10 ppm increased the dry matter yield significantly. Highest Fe concentration (408.12 ppm) was recorded in 40 ESP soil followed by 20 ESP (395.2 ppm). Salinity alongwith marginal or higher alkalinity reduced harmful effect of alkalinity. The uptake of Fe was the highest in normal soil due to the high dry matter yield. All the three sources increased the concentration of Fe and its uptake than the control in all the soils but did not show much distinction among themselves.The concentration of Mn decreased more with the increase in alkalinity than salinity but salinity with alkalinity improved Mn concentration. Similarly uptake of Mn also decreased sharply with the increase in salinity and alkalinity. The application of Fe sources decreased Mn concentration but increased the uptake. The highest decrease was caused with FeSO₄ and lowest with Fe rayplex.Like Mn the concentration and uptake of P decreased with the increased levels of salinity and alkalinity. The addition of Fe decreased the concentration of P, highest depression being with Fe KE-MIN.Increase in ESP increased the concentration and the uptake of Na greatly. Addition of Fe through all the sources increased Na concentration and uptake significantly but sources did not differ much in their effect on Na.     

Influence of phosphorus and zinc fertilizers on the uptake of P and Zn by corn plants grown in highly calcareous soils

Summary The influence of heavy applications of P (100, 200 and 400 ppm P) and Zn (12.5 and 25 ppm) fertilizers on their extractabilities, availabilities and uptake by corn grown in highly calcareous soil was investigated.A significant increase was found in the levels of (NH₄)₂CO₃-EDTA-extractable Zn either by Zn-applications alone or together with P. The amounts of NaHCO₃-extractable P were also increased with P additions and the influence of Zn applications was not clear.Phosphorus application generally increased the plant dry weight. In the soils treated with P and Zn fertilizers, that increase was mostly related to P rather to Zn.In the soils not treated with Zn, P additions increased Zn uptake by the plants. On the other side, in the soils treated with Zn, P additions decreased Zn uptake.Phosphorus concentration in the whole plant and/or in the different plant parts was increased by P application without being significantly affected by Zn addition. The plants showed greater response to 12.5 ppm Zn application than to 25 ppm.Plants grown for 4 weeks contained lower amounts of Zn relative to those grown for 8 weeks. The influence of plant age on P content was not as clear as occurred with Zn.     

Increased Phosphorus Uptake by Wheat and Field Beans Inoculated with a Phosphorus-Solubilizing Penicillium bilaji Strain and with Vesicular-Arbuscular Mycorrhizal Fungi

Greenhouse and field experiments were conducted to test the effect of a P-solubilizing isolate of Penicillium bilaji on the availability of Idaho rock phosphate (RP) in a calcareous soil. Under controlled greenhouse conditions, inoculation of soils with P. bilaji along with RP at 45 μg of P per g of soil resulted in plant dry matter production and P uptake by wheat (Triticum aestivum) and beans (Phaseolus vulgaris) that were not significantly different from the increases in dry matter production and P uptake caused by the addition of 15 μg of P per g of soil as triple superphosphate. Addition of RP alone had no effect on plant growth. Addition of vesicular-arbuscular mycorrhizal fungi was necessary for maximum effect in the sterilized soil in the greenhouse experiment. Under field conditions, a treatment consisting of RP (20 kg of P per ha of soil) plus P. bilaji plus straw resulted in wheat yields and P uptake equivalent to increases due to the addition of monoammonium phosphate added at an equivalent rate of P. RP added alone had no effect on wheat growth or P uptake. The results indicate that a biological system of RP solubilization can be used to increase the availability of RP added to calcareous soils.     

The development of potential screens based on shoot calcium and iron concentrations for the evaluation of tolerance in Egyptian genotypes of white lupin (Lupinus albus L.) to limed soils

European cultivars of white lupin (Lupinus albus L.) grow poorly in limed or calcareous soils. However, Egyptian genotypes are grown successfully in highly calcareous soil and show no stress symptoms. To examine their physiological responses to alkaline soil and develop potential screens for tolerance, three experiments were conducted in limed and non-limed (neutral pH) soil. Measurements included net CO2 uptake, and the partitioning of Fe2+ and Fe3+ and soluble and insoluble Ca in stem and leaf tissue. Intolerant plants showed clear symptoms of stress, whereas stress in the Egyptian genotypes and in L pilosus Murr. (a tolerant species) was less marked. Only the intolerant plants became chlorotic and this contributed to their reduced net CO2 uptake in the limed soil. In contrast, Egyptian genotypes and L pilosus showed no change in net CO2 uptake between the soils. The partitioning of Ca and Fe either resulted from the stress responses, or was itself a stress response. L pilosus and some Egyptian genotypes differed in soluble Ca concentrations compared with the intolerant cultivars, although no significant difference was apparent in the Ca partitioning of the Egyptian genotype Giza 1. In a limed soil, Giza 1 maintained its stem Fe3+ concentration at a level comparable with that of plants grown in non-limed soil, whereas stem [Fe3+] of an intolerant genotype increased. Gizal increased the percentage of plant Fe that was Fe2+ in its leaf tissue under these conditions; that of the intolerant genotype was reduced. The potential tolerance of the Egyptian genotypes through these mechanisms and the possibility of nutritional-based screens are discussed.     

The effect of soil moisture on the tolerance of Lupinus pilosus genotypes to a calcareous soil

Commercial narrow-leafed lupins (Lupinus angustifolius L.) grown on calcareous soils commonly display chlorotic symptoms resembling Fe deficiency. The severity of chlorosis increases with concurrent increases in soil moisture content. Our research has indicated that the rough-seeded lupin species, Lupinus pilosus Murr., has a range of adaptation to calcareous soils, from tolerant to intolerant. A pot experiment was conducted comparing a tolerant, a moderately tolerant and a moderately intolerant genotype of L. pilosus. Plants were grown for 35 days in a calcareous soil (50% CaCO₃) at three moisture contents (80%, 100% and 120% of field capacity); the growth was compared with that on a fertile black cracking clay control soil at 70% of field capacity. Visual chlorosis score, chlorophyll meter readings, number of leaves and shoot dry weights were recorded at 14, 21, 28 and 35 days after sowing. Concentrations of chlorophyll, active Fe and nutrients in the youngest fully expanded leaves were also measured. Results showed that increased soil moisture increased the severity of chlorotic symptoms (increased chlorosis score) in all genotypes. The tolerant genotype showed significantly less symptoms than other genotypes at all moisture contents. All genotypes were able to recover from chlorosis symptoms at 80% moisture in the calcareous soil. Chlorosis score negatively correlated with chlorophyll meter readings, chlorophyll concentration and foliar active and total Fe, and Mn concentrations. Visual chlorosis score appeared to be a cost effective, accurate and efficient method enabling classification of the tolerance of genotypes. The chlorotic symptoms were likely to be due to HCO₃ ^- induced nutrient deficiencies or a direct effect of HCO₃ ^- on chlorophyll synthesis. This study indicates that the most probable mechanism of tolerance is related to an ability to prevent uptake of HCO₃ ^- or efficiently sequester it once inside the root which prevents increases in internal pH and transport to the shoots.     

The effectiveness of soil-applied FeEDDHA treatments in preventing iron chlorosis in soybean as a function of the o,o-FeEDDHA content

The application of FeEDDHA products is the most common practice to prevent or to remedy Fe chlorosis in crops grown on calcareous soils. These products consist of a mixture of EDDHA components chelated to Fe. In this study such mixtures have been divided into four (groups of) components: racemic o,o-EDDHA, meso o,o-EDDHA, o,p-EDDHA and rest-EDDHA. Because the physical and chemical properties of these components differ, so does their effectiveness in delivering Fe to the plant. This effectiveness has not yet been examined in soil application, but needs to be understood to come to an adequate Fe fertilization recommendation. In this study the influence of composition of FeEDDHA treatments on Fe uptake by soybean plants (Glycine Max (L.) Merr. cv. Mycogen 5072) grown on calcareous soils was examined in two pot trials involving eight soils. The FeEDDHA treatments were equal in Fe dose but differed in o,o-FeEDDHA content, and were applied prior to the set in of chlorosis. The o,o-FeEDDHA content largely determined the Fe concentration in the pore water. In turn, in soils that induced chlorosis, the Fe concentration in the pore water determined the Fe uptake. The relationship between Fe concentration and Fe uptake is non-linear: initially Fe uptake increases strongly with increasing Fe concentration, but the slope flattens and a plateau is reached. FeEDDHA treatments increased both yield (up to 30%) and Fe content of the plant tissue (up to 50%). From FeEDDHA products with a higher o,o-FeEDDHA content, a smaller Fe dose is required to obtain the same results in terms of yield and Fe nutritional value.     

Preliminary evaluation of H2SO4 application methods to soils

Summary The effects of sulfuric acid application to soils and water on growth and chemical composition of sorghum (Sorghum bicolor) were compared in a greenhouse experiment using high sodium bicarbonate irrigation water. Significant increases in dry matter yield and plant uptake of P en Fe were produced only by soil treatment of calcareous soils.Contribution from the Department of Soils, Water and Engineering, The University of Arizona, Tucson, Arizona 85721, as Technical Paper No. 2320. This work was supported by the Arizona Mining Association.Research assistants and Professor     

Organic solid wastes from urban environment as iron sources for sorghum

Sorghum (Sorghum bicolor L. Moench) which is susceptible to Fe deficiency was grown in two different soils in a glasshouse with two different organic urban wastes (sewage sludge and dog manure) to ascertain their ability to supply Fe and other micronutrients to plants. One soil was calcareous with a history of Fe deficiency. Sewage sludge and dog manure at an application rate of 15,000 g/g to this soil effectively supplied Fe to plants. This effect was not present when the ash rather than the organic matter was used. Ferrous sulfate and Fe-EDDHA (Fe[ethylenediamine di-0-hydroxyphenylacetate]) likewise were not effective. Infrared spectra revealed differences in the fulvic acid for the two sources of solid wastes. The results imply that some sources of organic wastes may be useful in prevention or correction of Fe deficiency in calcareous soils.     

Mechanisms of microbially enhanced Fe acquisition in red clover (Trifolium pratense L.)

Soil microorganisms may play an important role in plant Fe uptake from soils with low Fe bioavailability, but there is little direct experimental evidence to date. We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil to investigate the role of soil microbial activity in plant Fe uptake. Compared with plants grown in non-sterlie (NS) grown plants, growth and Fe content of the sterile(s) grown plants was significantly inhibited, but was improved by foliar application of Fe EDTA, indicating that soil microbial activity should play an important role in plant Fe acquisition. When soil solution was incubated with phenolic root exudates from Fe-deficient red clover, a few microbial species thrived while growth of the rest was inhibited, suggesting that the Fe-deficient (-Fe) root exudates selectively influenced the rhizosphere's microbial community. Eighty six per cent of the phenolic-tolerant microbes could produce siderophore [the Fe(III) chelator] under -Fe conditions, and 71% could secrete auxin-like compounds. Interestingly, the synthetic and microbial auxins (MAs) significantly enhanced the Ferric reduction system, suggesting that MAs, in addition to siderophores, are important to plant Fe uptake. Finally, plant growth and Fe uptake in sterilized soil were significantly increased by rhizobia inoculation. Root Fe-EDTA reductase activity in the -Fe plant was significantly enhanced by rhizobia infection, and the rhizobia could produce auxin but not siderophore under Fe-limiting conditions, suggesting that the contribution of nodulating rhizobia to plant Fe uptake can be at least partially attributed to stimulation of turbo reductase activity through nodule formation and auxin production in the rhizosphere. Based on these observations, we propose as a model that root exudates from -Fe plants selectively influence the rhizosphere microbial community, and the microbes in turn favour plant Fe acquisition by producing siderophores and auxins.     

Iron accumulation in seed of common bean

The effect of soil and genotype on iron concentration [Fe] in common bean (Phaseolus vulgaris L.) seed was studied in the greenhouse. Liming an acid soil increased soil pH from 6.0 to 7.3 but had no effect on seed [Fe] of three bean genotypes (Voyager, T39, UI911) from the Middle American gene pool in North Dakota. However, liming decreased seed-manganese concentration [Mn]. The influence of FeEDDHA on Fe accumulation in seed of the three bean genotypes, grown on acid (pH=6.0) and naturally calcareous (pH=8.2) soils, was also studied in North Dakota. Seed from the acid soil contained 25% higher [Fe] than seed from the calcareous soil. FeEDDHA increased seed [Fe] only on the calcareous soil, but reduced seed [Mn] on both soils. Voyager seed, characterized by a relatively low [Fe] in the seed coat, had a higher seed [Fe] than the other two genotypes. The hypothesis that high seed [Fe] is characterized by a low seed-coat [Fe] was next investigated. Voyager, T39 and 10 diverse Latin American genotypes from the Middle American gene pool were grown on a soil (pH=7.0) with Andic properties in Mexico in the presence and absence of FeEDTA. FeEDTA increased seed [Fe]. Seed of Voyager and a Mexican genotype (Bayo 400) had the highest seed [Fe]. However, Bayo 400, unlike Voyager, contained a high percentage of its seed Fe in the seed coat. Consequently, a high seed [Fe] genotype does not necessarily have a low seed-coat [Fe]. Both soil and genotype affect Fe accumulation in bean seed.     

Effect of farm yard manure and iron on dry matter yield and nutrients uptake by oats (Avena sativa)

A pot culture experiment was conducted on a loamy sand soil to study the effect of FYM and Fe on dry matter yield and uptake of nutrients by oats (Avena sativa) crop in green-house. Application of Fe @ 5 and 20 ppm increased dry matter yield by 5.11 and 11.55 per cent, respectively. The per cent increase in dry matter yield over control with the application of 0.5 and 1.0 percent FYM was 19.06 and 30.07, respectively. Application of FYM increased concentration and uptake of P significantly. Phosphorus uptake increased by 23.60, 54.38, 91.01 and 134.61 per cent over control with 0.5, 1.0, 2.0 and 4.0 per cent FYM, respectively. Phosphorus concentration decreased at 20 ppm Fe but uptake increased significantly at 5 ppm Fe. Concentration and uptake of Ca increased with increasing amounts of Fe and application of FYM decreased concentration of Ca but uptake increased upto 1.0 per cent FYM over control. The Mg concentration and uptake decreased significantly with increased amount of Fe. Application of FYM also decreased Mg concentration but its uptake increased upto 1.0 per cent FYM and then decreased.Iron concentration and uptake increased upto 2 per cent FYM and then decreased. Whereas concentration of Fe decreased with increased amount of applied Fe but its uptake increased nonsignificantly with increased amount of added Fe.Managenese concentration and uptake decreased significantly with increased amount of applied Fe. Managenese concentration increased upto 0.5 per cent FYM but its uptake continued increasing with increasing amounts of applied FYM.     

Improving fertiliser efficiency on calcareous and alkaline soils with fluid sources of P,N and Zn

Alkaline calcareous or sodic soils represent an important proportion of the world's arable soils and are important for cereal production. For calcareous soils in general, despite high applications of P fertiliser for many years, P deficiency in cereals is common. Field experiments were conducted to test the relative ability of granular (e.g. DAP, MAP and TSP) and fluid fertilisers to supply P to wheat on grey calcareous and red brown calcareous sandy loam soils (Calcixerollic xerochrepts). A pot experiment was also conducted with these soils and with two non-calcareous alkaline soils to investigate the effects of placement on the efficiency of fertiliser performance. In 1998, fluid and granular sources of P, N and Zn were compared in the field by banding below the seed at sowing. In 1999, MAP applied as granular, and technical grade MAP applied as fluid, were compared as sources of P in rate response experiments. First year results showed that fluid sources of P, N and Zn produced significantly more grain than the granular product. In the following year, fluid fertilisers were found to produce significantly higher response curves for shoot dry weight, grain yield and P uptake in grain. At a commercial rate of 8 kg P ha^–1, fluid fertiliser produced between 22% and 27% more grain than the granular product. Soil moisture and fertiliser placement effects are implicated in the higher efficiency of fluid fertilisers.     

Amelioration of growth reduction of lowland rice caused by a temporary loss of soil-water saturation

Decreases in nutrient availability after loss of soil-water saturation are significant constraints to productivity in lowland rainfed rice soils. The effectiveness of soil amendments like lime and straw in ameliorating these constraints are poorly understood. This pot experiment was conducted in Cambodia to investigate changes in soil chemical properties and nutrient uptake by rice after applying lime or straw to continuously flooded or intermittently flooded soil. In continuously flooded soils, exchangeable Al decreased to below 0.2 cmolc/kg. Liming (pH 6.5–6.8) the continuously flooded soil decreased the levels of acetate extractable Fe and P, plant P uptake and shoot dry matter, but had no effect on either Bray-1 or Olsen extractable P values. By contrast, the addition of straw (3.5 g dry straw/kg soil) increased Bray-1, Olsen, and acetate extractable P, plant P uptake, shoot P, and shoot dry matter. The non-amended soils became strongly acidic after loss of soil water saturation: extractable Al increased to 1.0 cmol_c/kg, a potentially harmful level for rice. By contrast, extractable P decreased markedly under loss of soil water saturation as did plant P uptake, shoot P, and shoot dry matter. With loss of soil water saturation, liming substantially depressed the levels of Al but it did not increase plant P uptake, shoot P, and shoot dry matter. Straw addition not only decreased extractable Al levels to well below 0.6 cmol_c/kg under loss of soil water saturation, but it also increased extractability of soil P, plant P uptake, shoot P, and shoot dry matter. Thus, in rainfed environments, the incorporation of straw may be more effective than liming to pH 6.8 for minimising the negative effects of temporary loss of soil-water saturation on P availability, P uptake, and growth of rice.     

Effect of Trichoderma asperellum strain T34 on iron, copper, manganese, and zinc uptake by wheat grown on a calcareous medium

Rhizosphere microbes may enhance nutrient uptake by plants. Here we studied the effect of Trichoderma asperellum inoculation on the uptake of Fe, Cu, Mn, and Zn by wheat (Triticum aestivum L) grown in a calcareous medium. To this end, an experiment involving two factors, namely Fe enrichment (ferrihydrite enrichment and non-enrichment of the growing medium), and inoculation/non-inoculation with Trichoderma asperellum strain T34, was performed twice under the same conditions. The increase in Fe availability as a result of ferrihydrite enrichment did not enhance plant dry matter production. The effect of T34 on the concentration of Fe, Cu, Mn and Zn, and the total amount of Cu, Mn, and Zn in the aerial parts differed depending on the degree of ferrihydrite enrichment. Inoculation with T34 increased Fe concentration in Fe-deficient media, thus revealing a positive effect of this microorganism on Fe nutrition in wheat. However, T34 significantly decreased the concentration and total amount of Cu, Mn, and Zn in the aerial parts, but only in ferrihydrite-enriched medium. This adverse effect of T34 on Cu, Mn, and Zn uptake by wheat plants may have been related to conditions of restricted availability where potential competition for nutrients between microorganisms and plants can be more marked.     

A comparison of some populations of Eucalyptus viminalis Labill. growing on calcareous and acid soils in Victoria,Australia

A study of populations of Eucalyptus viminalis found on both acid and alkaline soils showed that seedlings differ in their tolerance of calcareous soils and their susceptibility to lime chlorosis. Seedlings from an open-forest population on calcareous dunes in the Otway Ranges, Victoria, averaged a significantly greater yield than seedlings of three other populations found on acid soils when all were grown on calcareous soil of pH 6.8. A tall ribbon gum form of E. viminalis, from Paradise gully in the Otways, was the least tolerant of alkaline conditions and showed severe signs of chlorosis and reddening of leaf margins. The latter appeared to be related to high uptake of phosphorus. This population showed rapid growth on a fertile acid loam. The data presented also emphasize the need to consider the variation in soils which can occur at any one site. Population differences were most marked when seedlings were grown on soils of pH near 7.0. Yield was reduced in the Otways calcareous population when seedlings were grown on the more leached soil from swales (pH 6.5) between dunes and on the highly calcareous soil from the dune crests (pH 7.8–8.0). The failure of any of the populations of E. viminalis studied to grow well on soils of high pH suggest that this species is not tolerant of highly calcareous soils. This may in part explain the absence of this species from the drier calcareous areas on the Mornington Peninsula and the Yanakie Isthmus, Victoria. Since seedlings had reduced root development on the soil collected from the Peninsula, E. viminalis may be restricted, in effect because of drought stress, to non-calcareous sites in the eastern part of Victoria.     

Residual effect of iron-nickel interactions on the availability of nutrients

Summary Residual value of micronutrients pair (Fe × Ni) has been investigated in a Cu-deficient and P-responsive red soil by growing a second crop of maize in which maize had already been grown with factorial combination of 4 levels of Fe and Ni. Dry matter yield (shoots) has been found to be lower (50%) in comparison to first year. Due to combined Fe and Ni treatments the concentration and uptake of Fe by shoots increased significantly while reverse was the case in roots, showing synergistic effect of Ni on Fe absorption and its significant translocation to shoots. Concentration and uptake of Mn by shoots and roots decreased at higher levels of Fe and Ni. Concentration of P in shoots decreased whereas concentration and uptake of Zn by shoots remained unchanged. Under the combined effect of Fe × Ni, maize roots contained more of nutrients as compared to shoots. Thus roots appear to be responsible for the recycling of micro and macronutrients in soils.     

Determination of threshold value of iron in soils and plants for the response of rice and lentil to iron application in calcareous soil

Summary In a pot experiment with 26 calcareous soils, the critical limit of Fe in soils and plants was evaluated. DTPA-extractable Fe was found significanty correlated with Bray's per cent yield in rice. The Fe²⁺ (iron) in rice and lentil was also found significantly correlated with DTPA-extractable Fe as well as Bray's per cent yield showing thereby the superiority of Fe²⁺ (iron) in leaves over DTPA-extractable soil Fe to differentiate Fe responsive soils from non-responsive ones. The total Fe content in plant tissues does not seem correlated with the occurrence of Fe deficiency. The threshold values of DTPA-extractable soil Fe and Fe²⁺ (iron) in rice and lentil leaves were 6.95, 44 and 74.5 ppm, respectively below which appreciable responses to Fe application were observed. The optimum Fe level for these soils was found to be 10 ppm in which the dry matter yield response in all the 19 rice soils and 16 lentil soils ranged from 14.28 to 56.16 (Av. 25.75%) and 13.31 to 53.97 (Av. 22.47%), respectively.     

The relative efficiency of zinc carriers on growth and zinc nutrition of corn

Summary A comparison of different zinc carriers showed that application of Zn-DTPA, Zn-EDTA, Zn-fulvate and ZnSO₄ significantly increased the dry matter yield and zinc uptake by corn over the control treatment where no zinc was applied. The chelates in particular enhanced to a greater extent the uptake of both native and applied sources than that observed with ZnSO₄ as the zinc carrier. Both the dry matter yield and zinc uptake by corn showed a positive and significant relationship with self-diffusion coefficient of zinc showing thereby that diffusion contributed mainly the supply of Zn from the ambient soil matrix to plant roots. The effectiveness of the chelates varied depending on their capacity to retain Zn in a soluble form in the soil solution.It is evident that zinc nutrition of plants in alkaline and calcareous soils can be more effectively regulated by both synthetic and natural chelates or organic manures which contain substantial amount of complexed zinc.Journal Paper No. 1 from the Department of Soil Science and Agric. Chemistry, Tirhut College of Agriculture, Dholi, Muzaffarpur, Bihar, India.     

Copper uptake and phytotoxicity as assessed in situ for durum wheat (Triticum turgidum durum L.) cultivated in Cu-contaminated, former vineyard soils

This work assessed in situ, copper (Cu) uptake and phytotoxicity for durum wheat (Triticum turgidum durum L.) cropped in a range of Cu-contaminated, former vineyard soils (pH 4.2–7.8 and total Cu concentration 32–1,030 mg Cu kg⁻¹) and identified the underlying soil chemical properties and related root-induced chemical changes in the rhizosphere. Copper concentrations in plants were significantly and positively correlated to soil Cu concentration (total and EDTA). In addition, Cu concentration in roots which was positively correlated to soil pH tended to be larger in calcareous soils than in non-calcareous soils. Symptoms of Cu phytotoxicity (interveinal chlorosis) were observed in some calcareous soils. Iron (Fe)–Cu antagonism was found in calcareous soils. Rhizosphere alkalisation in the most acidic soils was related to decreased CaCl₂-extractable Cu. Conversely, water-extractable Cu increased in the rhizosphere of both non-calcareous and calcareous soils. This work suggests that plant Cu uptake and risks of Cu phytotoxicity in situ might be greater in calcareous soils due to interaction with Fe nutrition. Larger water extractability of Cu in the rhizosphere might relate to greater Cu uptake in plants exhibiting Cu phytotoxic symptoms.