長期無施肥栽培桑園の土壌全窒素含量および全炭素含量と収量の推移 Changes in Total Nitrogen and Total Carbon Contents in Soil and the Leaf Yield of a Long-Term Unfertilized Mulberry under Field Condition

この論文にアクセスする

この論文をさがす

著者

抄録

1985年から無施肥裁培(以下、無施肥区)と化学肥料連用裁培(以下、施肥区)を長期間継続する桑園の土壌全窒素含量および全炭素含量と収量の推移を2003年までの19年間にわたって比較した。施肥区へは、年間10a当りN、P、Kをそれぞれ30kg、20kg、20kgを春と夏に半量ずつ表面施肥し、無施肥区へは何も施さず、雑草や落葉も圃場外へ除いた。調査園では、1985-1990年までの期間は在来の桑(品種:改良鼠返)が、1991年以降は改植した桑(品種:一ノ瀬)が裁培された。収穫法は、春蚕期は条桑収穫、晩秋蚕期は頂部4-5葉を残し下部を摘葉収穫とした。その結果、無施肥で裁培を長期間継続した圃場において、土壌全窒素含量と全炭素含量がおおむね平衡に保たれ、年間の桑生葉収量も1800-2000gm-2と安定していることが認められた。植物体によって収奪された窒素量と土壌全窒素含量の収支から、平衡に達した無施肥裁培では年間17.5gm-2の窒素の天然供給が推定された。この窒素のソースは不明であったが、土壌全窒素含量および全炭素含量の変動から、それらとして下層土から上層の根圏への養分移動、圃場周囲からの養分流入ならびに土壌中の微生物による大気からの窒素固定とが可能性として考えられた。桑葉収穫後、次の収穫までの期間が長く、かつ当年の施肥効果が現れるのが遅い春蚕期収量では無施肥区が、また収穫までの期間が短く当年の施肥への依存度が高い晩秋蚕期収量では施肥区が、それぞれ多収を示した。吸収した養分の分配も、施肥・無施肥処理区間に差が認められ、養分の少ない無施肥区では葉身部への窒素の配分割合が施肥区よりも高く、このことも無施肥裁培の高い収量の一因と考えられた。

Total nitrogen and total carbon contents of the soil and the leaf yield in a long-term unfertilized mulberry field (NF) were compared with those in a chemically fertilized field (F) for 19 years from 1985 to 2003. Each year, 30, 20 and 20gm^<-2> of nitrogen, phosphorus and potassium, respectively, were applied to the F field; a half in spring and the remaining half in summer. Weeds and litter fall were all removed from both F and NF fields. Originally, the mulberry cultivar Kairyonezumigaeshi had been grown in both fields for more than 25 years. In the spring of 1991 (the 7th year of the experiment), mulberry (cv. Ichinose) was replanted to both fields. The mulberry leaves were harvested twice a year in spring and in late-autumn, by cutting and leaf plucking methods, respectively. Total soil nitrogen and carbon contents of the soil in the NF field reached equilibrium after 15 years of treatment, and the yearly yield of fresh leaves from NF was stable at 1800 to 2000gm^<-2> for 5 years after replanting. The changes in nitrogen content of the plant and that of soil nitrogen suggested 17.5gm^<-2> of nitrogen was annually input to the NF field from the natural environment. The source of nitrogen input remains unknown, but a major part of nitrogen was supposed to come from the nitrogen pool in the subsoil layers, from adjacent environment and/or through atmospheric nitrogen fixation. In the spring rearing season, during which the time interval between successive harvesting was long and fertilizer application was less effective, the leaf yield was higher in the NF field than in the F field. On the other hand, in the late-autumn rearing season, during which intervals between successive harvesting was short and applied fertilizer was effective, the leaf yield was higher in the F field than in the NF field. The rate of nitrogen content allocation to leaf blades was higher in the NF than in the F field, even though the nitrogen content of the whole plant was lower in the NF field. The characteristic nutrient distribution pattern in the plant may also be a reason for the higher leaf yield in the unfertilized field.

収録刊行物

  • 日本作物學會紀事

    日本作物學會紀事 75(1), 28-37, 2006-01-31

    日本作物學會

参考文献:  36件中 1-36件 を表示

被引用文献:  1件中 1-1件 を表示

各種コード

  • NII論文ID(NAID)
    110004101403
  • NII書誌ID(NCID)
    AN00189888
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    00111848
  • NDL 記事登録ID
    7820759
  • NDL 雑誌分類
    ZR7(科学技術--農林水産--農産)
  • NDL 請求記号
    Z18-342
  • データ提供元
    CJP書誌  CJP引用  NDL  NII-ELS  IR 
ページトップへ