Wataru Sunohara

Comparison of No-tillage Farming among the Three Different Soils III. Adoption to the Volcanic Soil (Soil Texture SiC).

わが国の畑作における不耕起栽培は,最 近までほ とんど体系的には研究されておらず,耕 地環境や歴 史的背景の異なる欧米での不耕起栽培技術の持つ意 義や問題点と,わ が国のそれとは異なると考えられ る2),3).さらには,国 内においても気候,土 壌の相違 から不耕起栽培のもたらす効果や問題点は地域によ って異なることが予測される.一 方,近 年とくに指 摘される栽培環境の見直しや保全の重要性,生 産コ ストの低減などからも不耕起栽培のもつ特徴が注目 されている.こ うした状況にありながら,わ が国で の大型機械の利用を前提とした畑作の不耕起栽培に 関する資料の蓄積は少ない.本 研究は,畑 作の不耕 起栽培に関する基礎資料を得る目的で,土 性の異な る3地 域で同時並行的に同一の基本設計のもとに比 較実験 を行 った もの で ある. 本 報 では,前 報1),7)までの火 山灰 土壌(東 京,土 性 L),砂 質 土壌(島 根,土 性LS)に 続 いて,新 潟 での 火山灰 土壌(土 性SiC)に お け る3年6作 の実 験結 果 につ いて報告 す る.

Assessment of No-tillage Farming. VI. Renovation of No-tillage Field Passed 11Years.

In this study, we practiced a renovation trial by plowing to the continuous no-tillage field passed 11 years. The field seemed to be deteriorated for cultivation judging from the changes of soil condition and crop yield. The renovation trial based on the two-factors experiment with three levels of tillage and three levels of materials for soil improvement was started at April in 1991.1) Water content of soil in NC (renovation of notillage plot) was equal to that in CC (continuous plowing plot), but soil hardness (penetration resistance) in NC was higher than that in CC.2) Field efficiency of plowing in NC was higher than that in CC. Depth of tillage in NC was equal to that in CC, but the average value of width of tillage estimated from total width of plowed area and number of furrow in NC was wider than that in CC.3) Fuel consumption per unit area in NC was 5% higher, and the consumption per unit time in NC was 14% higher than those in CC.4) Specific resistance of soil estimated from the measured values, such as fuel consumption and traveling speed, in NC was higher by 8% than that in CC.5) From the result of analysis of variance for dry matter yield of corn, there was the significant difference with 1% level for tillage factor only. When we adopted the value of 100 to crop yield in CC as a standard, the crop yield in NC was 97, that was 67 in NN (continuous no-tillage plot), respectively.6) From the result of analysis of variance for the quantity of weed, there was the significant difference with 5% level for the tillage factor only. The quantity of weed in NN was much than any other plots.7) In NN, notable pH drop was observed at the soil layer of 5-10cm in depth. The pH profile in NN at the layer of 0-20cm approached to that in CC which showed an uniform distribution of pH.8) In spite of the deteriorated field by continuous no-tillage farming for 11 years, the crop yield almost recovered to the yield level in CC by only once tillage as a renovation.

Farm work system in loess plateau in China. 1. General condition of loess plateau and the sequence of grops at the surveyed village.

The authors made the survey of usual farm works for improving the cropping system as a part of the researches on the greenification of the loess plateau in China.In this paper, we described social and natural conditions of the loess plateau and agricultural indices of the surveyed district, and then the results of the survey which was carried out on the sequence of crops at one village.It was estimated that there were two kinds of crop-rotations. One was 4 years rotation, i.e. pes→wheat→millet or flax (edible oil), and another was 5 years rotation, i.e. pea→wheat→wheat→wheat→millet or flax (edible oil).Specific characters of estimated sequence of crops were discussed from the view points of trapping and holding rain-water in soil, fertility of soil, securing of food and edible oil, and seasonal dispersion of labor force.