Japanese Journal of Soil Science and Plant Nutrition
Online ISSN : 2424-0583
Print ISSN : 0029-0610
Volume 87, Issue 5
Displaying 1-29 of 29 articles from this issue
Original Paper
  • Satoshi NAKAMURA, Toshio IMAI, Kazunobu TORIYAMA, Satoshi TOBITA, Ryoi ...
    2016 Volume 87 Issue 5 Pages 338-347
    Published: October 05, 2016
    Released on J-STAGE: October 06, 2017
    JOURNAL FREE ACCESS

    The solubility of low-grade phosphate rock produced in Burkina Faso can be improved by calcination with sodium carbonate. Here, we tested the effects of this “calcinated Burkina phosphate rock” (CBPR) on soil condition and crop growth in greenhouse pot experiments, growing maize in upland conditions and lowland rice in submerged conditions. When a large rate (0.94gP kg-1 soil) of phosphate was applied, CBPR had a smaller effect on crop production than triple superphosphate (TSP). Although CBPR gave a lower soil-solution P concentration in the initial plant growth stage than TSP, possibly reflecting a low P supply from CBPR at this stage, it CBPR improved P fertility similarly to TSP. However, it also caused sodium accumulation and an increase in soil pH. When CBPR and TSP were applied at several rates, a lower rate of CBPR gave better growth than a higher rate. At 0.87 g P per pot, although maize growth was inhibited considerably, dry matter yields of rice with CBPR were similar to those with TSP. The optimum rates of CBPR application under the experimental conditions were calculated to be 0.5 g P kg-1 for maize and 0.3 g P kg-1 for rice. High rates or regular application of CBPR might inhibit plant water uptake or harm the soil owing to its strong alkalinity (pH 11) and large content of sodium. The optimum application rate needs to be determined in careful consideration not only of plant growth and yield, but also of the soil base balance and pH. Further investigation of the effects of CBPR application under field conditions is required.

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  • Ryo SHOJI, Tetsuya IWASE
    2016 Volume 87 Issue 5 Pages 348-355
    Published: October 05, 2016
    Released on J-STAGE: October 06, 2017
    JOURNAL FREE ACCESS

    The properties of humic substances, which account for the majority of organic matter in water and soil, depend on their origin. To estimate heavy metal toxicity in soils, it is important to understand which characteristics of humic substances determine the speciation of heavy metals, and to examine whether interactions among soil particles, humic substances, and heavy metal ions affect toxicity. We extracted four sets of humic acids from wood and soils and analyzed the binding of protons and cupric ions to three types of binding sites on the humic acids. The results were fitted to the NICA (non-ideal competitive adsorption)–Donnan model and compared directly with predictions based on generic parameters. Copper- binding data, which provided quantitative estimates for functional groups, showed that the properties of soil humic acids of diverse origin are homogeneous, whereas those of wood humic acids vary widely. Consistent differences between soil and wood humic acids are revealed at the level of functional group concentrations.

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