緑肥に期待される効果 堆肥との比較
Expected effects of green manure in comparison with the effects of compost.
Kiyoshi Tsutsuki,
Obihiro University of Agriculture and Veterinary Medicine
This is how K. Tsutsuki considers. No general conclusion.
1) 地力の向上 Increase soil fertility Green manure (G) = Compost (C) 緑肥植物に含まれる養分が、分解後放出される
Nutrients in green manure will be released on decomposition.
2) 土壌物理性の改善 Improve soil physical properties. G = C 有機物のすきこみによって土壌中の孔げきが増える。
Increase soil pore space by organic matter application.
3) 透水性の改善 Increase water permeability in soil G > C
緑肥作物の根は深く、下層の硬盤も突き抜けて伸びていくため、水はけをよくする。
Root of green manure is long and strong. It penetrates through a hard sublayer soil.
Therefore, it improves water drainage.
4) 連作障害の回避 G >= C Suppress the problems associated with continuous cropping.
土壌病害の抑制 suppress plant pathogenic microbes G >= C 線虫の抑制 suppress the activity of nematodes G > C 土壌微生物活性の増大 increase the activity of soil microbes G = C 5) 菌根菌の増加 Increase arbuscular mycorrhizal fungi. G > C 6) 根粒菌の増加 Increase root nodule bacteria/ Rhizobium. G > C
7) 雑草の抑制 Suppress weeds G > C アレロパシー Allelopathy
8) 環境保全への貢献 Contribution to environmental conservation G > C a. 土壌侵食の防止 Soil erosion is suppressed by cover crop. G > C b. 過剰養分の吸収、有機物分解に伴う無機態窒素の固定 only G
Growing green manure absorbs excess nutrients in soil. Fix mineral nitrogen temporarily into decomposing organic matter.
c. 重金属の吸収 （ファイトレメディエーションへの貢献） only G Absorb heavy metals (contribute to phyto-remediation)
d. 農村景観への貢献 only G Contribute to the beautiful scenery of rural area.
e. 緑肥による大気中二酸化炭素の固定。 有害ガスを発生しない。
Fix CO2 in air. No emission of harmful gasses.
利用上の利点 (Merits on using) 1) 大面積に均一に施用できる
Green manure can be applied uniformly to large area. G > C 2) 施用される有機物の品質が均一
Quality of organic matter applied to the field is uniform. G > C 3) 労力は堆肥施用の場合よりも少ない。輸送コストがかからない。
Labor may be less compared with compost application. No transportation cost is necessary. G > C
利用上の欠点 (Demerits on using )
1) 緑肥による逆効果 Adverse effects G = C
分解未熟 → 発芽障害、立ち枯れ Stunt due to insufficient decomposition 高C/N → 窒素飢餓 Nitrogen starvation due to high C/N
不適切な選択 → 連作障害、病虫害の増大 Transfer decease and worm hazards due to improper combination of green manure and following crop
2) 緑肥栽培中の休閑が必要
Need fallow period for growing green manure G < C 3) 緑肥効果は緑肥の種類によって異なるためオールマイティではない
Effect of green manure may differ by each species of green manure, Therefore, almighty effects are not expected.
4) 緑肥と後作物の組み合わせに注意
Combination between green manure and following crop should be considered.
5) 緑肥すきこみで線虫が増加する例もある
Green manure sometimes increases nematodes by mixing into soil.
6) 種子が高価 しかし純粋な良い種が必要
Seeds of may be expensive, but pure and good seed is necessary.
7) 緑肥の雑草化・野草化
Turn to weed or wild grass on improper management.
