Carbon dioxide circulation to harmonize global environmental aspect with crop production

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With an aim of contributing from agricultural side to prevent the progress of global warming, we carried out the factorial experiment on a field composed of tillage method (two levels ; conventional tillage (CT) / no-tillage (NT)) x cropping style (three levels ; single cropping/ single cropping/ mixed cropping) x treatment of weeding (weeding/ no-weeding) x repetition (three plots), and measurement of soil respiration rate on a field from December in 1995 to August in 1996.From the experimental result, (1) The dry matter yield of weed in single cropping was more than that in mixed cropping, and the yield in NT plot was more than that in CT plot. (2) The dry matter yield of leaf and stem of crops in CT plot was more than that in NT plot at the first and the third croppings in case of barley and wheat, but the yield in NT was more than that in CT plot at the second cropping in case of sorgo and corn. (3) In dry matter yield of grain, the first, the second and the third in order were "weeding", "weeding" and "no weeding", respectively, at the first and the third croppings. (4) In fixed carbon dioxide by plants calculated from the total dry matter yield and its conversion value, there was no notable difference between in NT plot and in CT plot. We compared the values of fixed carbon dioxide by all plants and the value of fixed by a deciduous trees in forest. From the calculated results, the notable effect of fixation by plants produced in no-tillage and mixed cropping on a field was shown. (5) In the measurement of soil respiration rate, there was no difference between in NT plot and in CT plot during crop growing period, but the value in NT plot was larger than that in CT plot during season without crop on a field.