【C/N比の算出方法】
有機物に含まれる炭素(C)と窒素(N)の質量比のことをC/N比と呼びます。
〈計算例〉
| 資材の名称 | 炭素(C) | 窒素(N) | 計算式 | C/N比 |
|---|---|---|---|---|
| 稲わら | 38.9% | 0.74% | 38.9%÷0.74% | 52.6 |
| 菜種油粕 | 43.0% | 5.61% | 43.0%÷5.61% | 7.7 |
【有機物の分解速度を左右するC/N比】
土壌中の微生物は有機物を分解する際に窒素を必要とします。有機物のC/N比が高い(概ね10以上)と分解速度が遅くなり、微生物の窒素消費量が増えるため、一時的に作物が利用できる窒素が減少する(窒素飢餓)可能性があります。 一方、C/N比が低い(概ね10以下)と分解が速やかに進み、土壌に窒素を供給しやすくなります。
〈おもな資材のC/N比〉
- 稲の残渣
- もみ殻：72.0
- 稲わら：52.6
- 緑肥
- ソルゴー：51.0
- クロタラリア：46.0
- 家畜ふん堆肥
- 牛ふん堆肥：18.9
- 豚ぷん堆肥：11.7
- 鶏ふん堆肥：9.6
- 肥料
- 菜種油粕：7.7
- 綿実油粕：6.8
- 魚粉：4.7
- 蒸製骨粉：4.4
- 蒸製皮革粉：3.5
参考文献
静岡県 経済産業部 農業局 地域農業課（2021）「静岡県土壌肥料ハンドブック」
https://www.pref.shizuoka.jp/sangyoshigoto/nogyo/nouyaku/1003320/1027218.html
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