97 research outputs found

    Efficiency of foliar application of sparingly soluble sources of boron and zinc in citrus

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    This study evaluated leaf supply of zinc (Zn) and boron (B) using either soluble or sparingly soluble fertilizers in young sweet orange trees. Three experiments were set up in a greenhouse to compare two sources and four doses (control, low, adequate and high) of fertilizers as follows: (i) Experiment I (B): boric acid and calcium borate; (ii) Experiment II (Zn): Zn sulfate and Zn oxide; and (iii) Experiment III (B + Zn): boric acid + Zn Sulfate and Zn Borate. The sparingly soluble sources were effective in increasing the Zn and B leaf concentration. Dry matter of the aerial part increased 18 % with B applications in adequate concentration independent of the B fertilizer sources. In contrast, trees did not grow well with applications of adequate concentration of Zn as Zn Sulfate or high Zn concentration as Zn borate. Superoxide dismutase activity in leaves increased with applications of low concentration of Zn as Zn oxide and decreased with high concentration of Zn from either source. Polyphenol oxidase activity increased with application of adequate concentration of B as boric acid and high concentration of B as calcium borate. Furthermore, the upper concentrations of Zn were toxic in orange trees when the source was Zn sulfate. Increases in plant growth without damage to leaf tissue and positive responses of key enzymes of orange trees in a range of nutrient concentration applications demonstrated the practical use of sparingly soluble fertilizers to supplying B and Zn foliarily to plants

    Nutrient Disorders of Sweet Potato

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    Crop Production/Industries,

    A commercial process development for plant food formulation using polyprotic acids from natural extracts as chelating agents

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    The citrus industry is one of South Africa's largest agricultural sectors in terms of export earnings with lemon fruits and juice as a trendsetter due to their high grade quality. According to growers, the Eastern Cape Province of South Africa alone produces an excess of about 10-14,000 tons of lemon juice which is presently of no economic value due to the sour taste and “bitterness”. As a result of this excess and in order to make use of the polyprotic acids naturally occurring in the lemon juice, four fertilizer nutrient mixtures are formulated, using lemon juice as base. From a conceptual scientific approach, characterization (physico-chemical and functional properties determinations) of Eureka Lemon fruit juices were undertaken, followed by smaller scale batch formulation experiments. On the basis that these lemon juice-based fertilizer mixtures are prepared following standard liquid fertilizer formulation guidelines, a field test was conducted to evaluate their potential effectiveness to influence plant growth. A growth chamber testing on tomato plants revealed high growth response (> 99.9 % certainty) potential in two of the semi-organic mixtures formulated while the organic mixture showed a relatively good growth rate as compared to the control (pure tap water). According to statistical analysis (ANOVA) comparison, two of the semi-organic mixtures performed considerably better than the two commercial samples evaluated. Potential benefits profoundly associated with these nutrient mixtures as compared to similar liquid fertilizer products on the market is that most nutrients are chelated and dissolved in solution. Also, the mixtures contain all necessary nutrients including plant growth substances required for healthier plant growth. The most important socioeconomic impact is the value addition to the technology chain in the citrus industry. The use of fluid fertilizers in significant quantities is less than twenty years old. Nevertheless, growth has been so rapid that in South Africa demand for mixed liquid fertilizer has greatly increased from 90 000 tons NPK & blended micronutrients in 1955 to more than 600 000 per annum tons today (Report 41/2003, Department of Minerals and Energy). The liquid fertilizers market is sparsely specialized with major competitors like Omnia, Kynoch and Foskor supplying more than 50 % of the market demand. Amongst the nutrient mixtures formulated, mixture one is an NPK (1-1-2) based nutrient mixture containing both secondary nutrients (0.5 % Mg & 1.0 % Ca) and seven micronutrients (0.1 % Fe, 0.05 % Cu, 0.05 % Zn, 0.05 % Mn, 0.02 % B, 0.0005 % Mo and 0.0005 % Co). The composition of this mixture offers the formula a potential to be used as a general purpose (all stages of plant growth) fertilization mixture in view of its balanced composition (containing all essential plant nutrients). Mixture two contains essentially the micronutrients and in higher concentrations (0.3 % Fe, 0.3 % Cu, 0.1 % Zn, 0.2 % Mn, 0.02 % B, 0.0005 % Mo and 0.0005 % Co) as compared to mixture one except for boron, molybdenum and cobalt. The concentration of the micronutrients contained in this mixture is adequately high which offers a potential for it to be used in supplementing nutrition in plants with critical micronutrient-deficient symptoms. Mixture three is very similar to mixture two (1.0 % Fe, 0.05 % Cu, 0.05 % Zn, 0.05 Mn, 0.05 % B, 0.0005 % Mo and 0.0005 % Co) except that the concentrations of all seven micronutrients are considerably less than those of contained in mixture two. However, the concentration of iron in this mixture is as high as 1.0 %. The mixture has a potential to be used in high iron-deficient situations. Mixture four is an organic formula with relatively low nutrient concentrations (NPK-0.02-0.02-1, 0.27 % Mg, 0.02 % Ca, 0.008 % Fe, 0.26 % Cu, 0.012 % Zn, 0.009 % Mn). Nevertheless, this mixture is appealing for organically grown crops where the use of chemicals is prohibited by standards. These lemon juice-based nutrient mixtures were further characterized and tested for stability and storability over a period of eight weeks. This study revealed no major change in the physical quality (colour, pH and “salt out” effect). The basic formulation methodology is a two-step procedure that involves filtration of the lemon juice to remove membranous materials, mixing at ambient temperature and stabilization of the nutrient mixtures. However, for the organic nutrient formula mix, filtration follows after extraction of nutrients from plant materials using the lemon juice

    The amendment of acid soil with an ettringitic waste and its effects on plant growth

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    Bibliography: pages 63-68.Associated with ESKOM's ash water beneficiation programme is the precipitation of an ettringitic waste from highly alkaline, saline water. The waste is dominated by ettringite (CauAJ4(OH)24(S04) 6.52H20) with calcite (CaC03) as a minor phase (17.7% for the sample used in this study). Apart from the presence of calcite, the ettringite itself is alkaline due to the presence of OH ions. Following a submission that the waste had potential as an ameliorant of acid soil, research into this possibility was initiated. Following the determination of a calcium carbonate equivalent (HCl-CCE) value of 78% using the HCl back titration method of Horwitz (1980), an incubation experiment was initiated using three acid soils of contrasting characteristics: a so-called Silvermine sand, Kranskop A and Kranskop B soils. The effects on soil acidity of ettringitic waste were compared with analytical grade calcite. Soils (50g samples) were incubated with the two alkaline amendments for two weeks, following which pH(KCl), pH(H20) and KCl-extractable acidity were determined. Ettringitic waste led to apparently lower levels of acidity neutralization for corresponding treatments set on an HCl-CCE basis. This difference was minimized with the highly buffered, sesquioxide and organic-rich Kranskop A soil which could be attributed to the greater reactivity of the ettringitic waste with organically-complexed acidity together with the "self-liming" effect of so4 in sesquioxide-rich soils (sensu Reeve & Sumner, 1972). The waste showed progressively less neutralization with Kranskop B and Silvermine soils apparently in response to a decline in buffering capacity of these soils

    Nutrient Disorders of Sweet Potato

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    Knowing Agricultural Chemicals

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    The purpose of this book is to present brief descriptions of various chemicals used in agriculture. Insects and weed pests will be discussed only incidentally, as they are the subjects of other volumes of this information series. The reader who wishes to make a more detailed study of agricultural chemicals should consult the Bibliography in Volume Six for additional reference material.https://openspaces.unk.edu/air-info/1000/thumbnail.jp

    Yam nutrition: Nutrient disorders and soil fertility management

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    Nutrição de ferro das plantas: química e fisiologia da sua deficiência e toxicidade

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    Iron deficiency and toxicity are important yield limiting factors in crop production around the world. In this review, an attempt is made to summarize the information on diagnosis of Fe deficiency and toxicity, chemistry of Fe in soil, mechanism of Fe uptake, role of chelates in Fe nutrition, factors affecting Fe availability to crop plants and measures required to correct Fe deficiency and toxicity. A brief discussion about Fe toxicity in flooded rice is also included. Information presented in this review article should provide a basis for correcting this nutritional disorder in crop plants, and indicates new research efforts needed to solve Fe stress problems.A deficiência e toxidez de Fe são fatores que limitam o rendimento das culturas. Nesta revisão é apresentado um resumo das informações sobre a diagnose da deficiência e toxidez química do Fe no solo, mecanismo de absorção, importância dos quelados de Fe na nutrição de plantas, fatores que afetam a disponibilidade de Fe e dos métodos de correção da deficiência e toxidez de Fe. É feita também uma discussão resumida sobre toxidez de Fe com arroz irrigado. Esta revisão fornece informações básicas para correção de desordens nutricionais que envolvem Fe, e sugere pesquisas a serem feitas visando solucionar problemas de estresse de Fe

    Bio-effectors for improved growth, nutrient acquisition and disease resistance of crops

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    Recent scientific approaches to sustain agricultural production in face of a growing world food demand, limited natural resources, and ecological concerns have been focusing on biological processes to support soil fertility and healthy plant growth. In this context, the use of bio-effectors, comprising living (micro-) organisms and active natural compounds, has been receiving increasing attention. In contrast to conventional fertilizers and pesticides, the effectiveness of bio-effectors is essentially not based on the substantial direct input of mineral plant nutrients, neither in inorganic nor organic forms, nor of a-priori toxic compounds. Their direct or indirect effects on plant performance are rather based on the functional implementation or activation of biological mechanisms, in particular those interfering with soil-plant-microbe interactions. The general objective of the present research work was to improve the empirical and conceptual understanding concerning the utilization of bio-effectors in agricultural practice, following the principles of plant growth stimulation, bio-fertilization and bio-control. One main aspect of investigation was the application of bio-effectors to improve the efficiency of phosphorus (P) acquisition by the plant. Promising bio-preparations based on microbial inoculants (e.g. Bacillus, Pseudomonas, Trichoderma species) as well as natural compounds (e.g. algae extracts, humic acids) were tested in screening assays, greenhouse, and field experiments to characterize their potential effectiveness under varying environmental conditions. The most significant effects on plants appeared under severely low phosphate availability, but even under controlled conditions, bio-effectors required a narrow range of conductive environmental settings to reveal their potential effectiveness. Another focus of research was the application of bio-effectors to control soil borne pathogens, which typically appear in unsound crop rotations. Emphasis was set on take-all disease in wheat induced by the fungus Gaeumannomyces graminis. While the effectiveness of oat precrops to control take-all in subsequent wheat has been attributed to microbial changes and enhanced manganese (Mn) availability in soils, the take-all fungus is known to decrease the availability of Mn by oxidation. Against this background, the effectiveness of oat precrops and alternative crop management strategies to improve the Mn status and suppress the severity of take-all in wheat was investigated under controlled and field conditions. In conclusion, none of the tested supplemental treatments, such the application of microbial bio-effectors, stabilized ammonium or manganese fertilizers, could fully substitute for the multiple effectiveness of oat precrops, which was further confirmed by the results of a field experiment. Finally, some general conclusions and perspectives are summarized. Selected bio-effectors showed a strong capacity to improve the nutrient acquisition and healthy growth of crop plants under controlled conditions, but not in field experiments. However, even under controlled conditions the strongest effects occurred when plants were exposed to abiotic or biotic stresses, such as severely limited P availability or pathogen infestation of the soil substrate, still restricting plant growth to unproductive levels. Facing this situation, there is no perspective to improve the field efficiency of promising bio-effectors applications as a stand-alone approach. The only chance to develop viable alternatives to the conventional use of fertilizers or pesticides, for an ecological intensification of agriculture that maintains high yield levels, seems to be a reasonable integration of bio-effectors into the whole crop management of sound agricultural practice.Angesichts eines weltweit wachsenden Bedarfs an Nahrungsmitteln, begrenzter natürlicher Ressourcen und ökologischer Probleme streben neuere wissenschaftliche Ansätze zur nachhaltigen Gestaltung der Landwirtschaft verstärkt die Nutzung biologischer Prozesse zur Föderung der Bodenfruchtbarkeit und eines gesunden Kulturpflanzenwachstums an. In diesem Zusammenhang hat der Einsatz von Bio-Effektoren, einschließlich lebender (Mikro-)Organismen und wirkaktiver Naturstoffe, wachsendes Interesse gefunden. Im Gegensatz zu konventionellen Düngemitteln und Pestiziden beruht die Wirksamkeit von Bio-Effektoren nicht auf dem substantiellen Direkteintrag von Pflanzennährstoffen, weder in anorganischer noch organischer Form, noch von a priori toxischen Stoffen. Die direkten oder indirekten Wirkungen von Bio-Effektoren auf die Pflanze basieren vielmehr auf der Implementierung oder Aktivierung von biologischen Wirkungsmechanismen, insbesondere solcher die mit den Interaktionen von Boden, Pflanze und Mikroorganismen interferieren. Ziel der vorliegenden Arbeit war es, das Verständnis zur Nutzung von Bio-Effektoren in der landwirtschaftlichen Praxis anhand der prinzipiellen Wirkungskategorien von direkter Stimulans des Pflanzenwachstums, biologischer Pflanzenernährung (bio-fertilization) und biologischem Pflanzenschutz (bio-control) zu erweitern. Ein Hauptaspekt galt der Anwendung von Bio-Effektoren um die Aneignungseffizienz von Phosphor (P) durch die Pflanze zu steigern. Aussichtsreiche Präparate, basierend auf mikrobiellen Inokula (z.B. Bacillus, Pseudomonas, Trichoderma Spezies) als auch Naturstoffen (z.B. Algenextrakte, Huminsäuren), wurden in Screeningassays, Gewächshaus- und Feldversuchen getestet um ihr Wirkungspotential unter variablen Umweltbedingungen zu charakterisieren. Die stärksten Effekte traten unter Bedingungen mit sehr geringer Phosphatverfügbarkeit auf, jedoch selbst unter kontrollierten Bedingungen war der Einfluss förderlicher und teilweise eng bestimmter Umweltfaktoren notwendig um die Wirksamkeit von Bio-Effektoren zu zeigen. Ein weiteres Thema war der Einsatz von Bio-Effektoren zur Bekämpfung bodenbürtiger Krankheitserreger, welche durch unausgewogene Fruchtfolgen gefördert werden. Die Untersuchungen befassten sich insbesondere mit der Schwarzbeinigkeit des Weizens, einer bedeutenden Wurzelkrankheit hervorgerufen durch den Pilz Gaeumannomyces graminis. Eine effektive Vorfrucht zur Bekämpfung der Schwarzbeinigkeit ist Hafer, was in Zusammenhang mit mikrobiellen Veränderungen im Boden und einer erhöhten Verfügbarkeit von Mangan (Mn) für die Folgefrucht Weizen gestellt wurde. Vor diesem Hintergrund wurde die Wirksamkeit von Hafer als Vorfrucht im Vergleich mit alternativen Maßnahmen des pflanzenbaulichen Managements zur Steigerung der Mn-Versorgung und Bekämpfung der Schwarzbeinigkeit in Weizen untersucht. Fazit war, daß keine der getesten Alternativmaßnahmen, wie die Anwendung mikrobieller Bio-Effektoren, stabilisierten Ammonium- oder Mangandüngers, die vielseitige Vorfruchtwirkung von Hafer vollständig substituieren konnte, was auch durch die Ergebnisse eines Feldversuches bestätigt wurde. Abschließend folgen generelle Schlussfolgerungen aus der vorliegenden Arbeit und sich daraus ergebende Perspektiven zur Nutzung von Bio-Effektoren. Ausgewählte Bio-Effektoren zeigten unter kontrollierten Bedingungen ein hohes Wirkungspotential zur Förderung der Nährstoffaneignung und des gesunden Wachstums von Kulturpflanzen, nicht jedoch in Feldversuchen. Zudem waren die stärksten Effekte dann zu beobachten, wenn die Pflanzen abiotischen oder biotischen Stresssituationen, wie stark limitierter P-Verfügbarkeit oder einem pathogenbelasteten Bodensubstrat, ausgesetzt waren, welche das Pflanzenwachstum auch weiterhin auf ein unproduktives Maß beschränkten. Diese Ergebnisse eröffnen keine Perspektive den praktischen Nutzen von Bio-Effektoren durch Einzelmaßnahmen zu steigern. Vielmehr schein der einzig erfolgversprechende Ansatz leistungsfähige Alternativen zum konventionellen Einsatz von Düngemitteln und Pestiziden für eine ökologische Intensivierung der Agrarproduktion auf hohem Ertragsniveau zu entwickeln, eine sinnvolle Integration von Bio-Effektoren in das gesamte pflanzenbauliche Management einer fachgerechten Landwirtschaft zu sein
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