85 research outputs found
Formas de adição de zinco a um formulado NPK e seu efeito sobre a produção de milho
Heavy metals in the irrigation water, soils and vegetables in the Philippi horticultural area in the Western Cape Province of South Africa
The aims of this study were to investigate the
extent of heavy metal contamination in the Philippi
horticultural area in the Western Cape Province, South
Africa. Concentrations of Cd, Cr, Cu, Mn, Ni, Pb and Zn
were determined in the irrigation water, soils and vegetables
in both winter and summer cropping seasons with
an ICP-AES and tested against certified standards.
Differences were found in heavy metal concentrations
between the winter and summer cropping seasons in the
irrigation water, soils and vegetables. Certain heavy
metals exceeded the maximum permissible concentrations
in the irrigation water, soils and vegetables produced
in South Africa. These toxic concentrations were
predominantly found in the summer cropping season for
the soils and in the crops produced in winter. It is thus
suggested that further studies are carried out in the
Philippi horticultural area to determine the sources of
the heavy metals to try and mitigate the inputs thereof
and therefore reduce the amount of heavy metals entering
the human food chain.ISI & Scopu
Influence of soil type and natural Zn chelates on flax response, tensile properties and soil Zn availability
A greenhouse experiment was conducted on weakly acidic and calcareous soils to evaluate the relative efficiencies of three natural Zn chelates [Zn-aminelignosulphonate (Zn-AML), Zn-polyhydroxyphenylcarboxylate (Zn-PHP) and Zn-S,S-ethylenediaminedisuccinate (Zn-S,S-EDDS)] applied to a crop textile flax (Linum ussitatisimum L.) at application rates of 0, 5 and 10 mg Zn kg−1. In the flax plant, the following parameters were determined: dry matter yield, soluble and total Zn concentrations in leaf and stem, chlorophyll, crude fibre, and tensile properties. For the different soil samples, the following parameters were determined: available Zn (DTPA-AB and Mehlich-3 extractable Zn), easily leachable Zn (BaCl2-extractable Zn), the distribution of Zn fractions, pH and redox potential. On the basis of the use of added Zn by flax, or Zn utilization, it would seem recommendable to apply Zn-S,S-EDDS at the low Zn rate in both soils. In contrast, adding the high Zn rate of this chelate to the weakly acidic soil produced an excessive Zn concentration in the plant, which caused a significant decrease in both dry matter yield and chlorophyll content. Furthermore, assessing available Zn with the DTPA-AB method proved the best way of estimating the level of excess Zn in flax plants. The soluble Zn concentration, which was established with 2-(N-morpholino)ethanesulfonic acid reagent (MES), of plant fresh and dry matter could be used as an alternative way of diagnosing the nutritional status of Zn in flax plants. In this experiment, the highest soil pHs were associated with the lowest redox potentials, which coincided with the smallest amounts of available Zn and water soluble Zn in soil, and the lowest levels of Zn uptake by flax plants
Residual effects of natural Zn chelates on navy bean response, Zn leaching and soil status
greenhouse experiment was conducted on weakly acidic and calcareous soils to evaluate the aging and residual effects of three natural organic Zn chelates [Zn-ethylenediaminedisuccinate (Zn-EDDS), Zn-polyhydroxyphenylcarboxylate and Zn-aminelignosulfonate] each administered in a single application to a first navy bean (Phaseolus vulgaris L.) crop at several different Zn application rates. In a second navy bean crop, we determined the following parameters: the extent of Zn leaching, the amount of available Zn remaining in soils, the amount of easily leachable Zn, the size of Zn fractions in soils, the pH and redox potential, the dry matter yield, and the soluble and total Zn concentrations in plants. The residual effect after 2 years of Zn fertilization mainly depended on the aging effect of Zn chelates and losses due to Zn leaching. The data relating to the evolution from the first to the second crop showed that the aging effect was noticeable in the calcareous soil. In the latter soil, the Zn-S,S-EDDS treatments showed greater decreases in the Zn uptake by plants than the other Zn treatments and the greatest Zn uptake by plants occurred when Zn was applied as Zn-aminelignosulfonate (10 mg Zn kg−1 rate, 6.85 mg Zn per lysimeter; 5 mg Zn kg−1 rate, 3.36 mg Zn per lysimeter). In contrast, in the calcareous soil, the maximum amount of Zn uptake, for the three chelates was 0.82 mg Zn per lysimeter. Consequently, a further application of Zn would be needed to prevent Zn deficiencies in the plants of a subsequent crop. The behaviour of the pH and Eh parameters in the soils and leachates did not depend on the natural Zn sources applied. In this study, the easily leachable Zn estimated by BaCl2 extraction was not adequate to predict Zn leaching from the soils in subsequent crops
Comparison of soil phosphorus fractions after 37 years of wheat production under different management practices in a semi-arid climate
Yield response and iron status of Japanese mint as influenced by soil and foliar applied iron
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