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Phyto-purification of livestock-derived organic waste by forage rice under subtropical climate |
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| Authors: | Kei Asada Taku Nishimura Chihiro Kato Koki Toyota Masaaki Hosomi |
| Institution: | 1. National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki, 305-8604, Japan 2. Graduate School of Agriculture and Life Sciences, University of Tokyo, Tokyo, 113-8657, Japan 3. Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, 184-8588, Japan 4. Department of Chemical Engineering, Tokyo University of Agriculture and Technology, Tokyo, 184-8588, Japan |
| Abstract: | Soil and water pollution caused by organic waste is a concern for livestock-breeding areas. Nitrogen balance in a paddy-field water-purifying system in which cattle feces were applied was studied for 4 years to assess the suitability of the system for a subtropical area, Japan. Three successive harvestings using ratoon of forage rice following one rice transplanting were conducted with chemical fertilizer and high and low rates of cattle-feces application. Nitrogen load was 81.3–495.0 kg N ha?1 year?1, while nitrogen uptake was highly dependent on the yield of the first harvesting. Annual variation of forage rice yields was large, ranging from 15.5 to 26.8 Mg ha?1 owing to fluctuation in the yield at second and later harvestings. On average, nitrogen was lost by leaching at a rate of 2.3–3.4 kg N ha?1 year?1. The nitrogen content in soil at a depth of 0–5 cm increased up to 12.2 kg N ha?1 over the 4-year period compared with that before the field experiment. However, continuous application of cattle feces could slightly increase the nitrogen content in soil at a depth greater than 35 cm. Our results showed the ability of flooded forage rice to remove nitrogen at up to 320.1 kg ha?1 year?1 for a field to which cattle feces were applied. Further investigation is needed to produce a high and stable yield at second harvesting each year, to prevent the accumulation of soil nitrogen, and to assess gaseous nitrogen loss. |
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