坡地蕉園平臺堦段栽培與農藝方法之效益

Abstract

本試驗於民國59年至65年，在南投縣集集鎮13°東南向坡地上舉行，其目的在比較水土保持工程(水平排水式平臺?段)與農藝方法(包括草帶法2.5公尺間距，草帶法5.0公尺間距及百喜草全面覆蓋與敷蓋)在香蕉園中何者效益最高。經6年之試驗，其結果可總括如下： (一)水土流失量：逕流量以百喜草全面覆蓋與敷蓋處理最小，淨耕區最大。土壤流失量與淨流量大小一致，百喜草全面覆蓋與敷蓋處理，4年內僅流失土壤0.364 tons/ha。 (二)香蕉產量：草帶法5.0公尺間距產量最高，淨耕區產量最低。百喜草全面覆蓋與敷蓋處理，亦可增產12.8%。 (三)土壤水分：乾旱季節以水平排水式?段土壤含水量最高，百喜草全面覆蓋與敷蓋處理及淨耕區最低。 (四)土壤滲透率即導水率：百喜草全面覆蓋與敷蓋處理最高。 (五)真假比重：各處理間變化微小。 (六)土壤有機質及其他土壤化學性質：百喜草全面覆蓋與敷蓋處理之有機質含量較多。如比較試驗前後期淨耕區之土壤有機質含量，則後期土壤中有機質含量減少的趨勢。各種處理土壤中有效磷、有效鉀及pH在試驗結束時均較試驗開始時增加。 (七)草帶法坡度減小程度以間距2.5公尺為大：由本試驗結果可知，在效益上水土保持農藝方法優於?段栽培。百喜草全面覆蓋與敷蓋處理對沖蝕控制及改良理化性雖有很好的效果，但主作物香蕉產量稍低，有待研究改進。草帶法5.0公尺間距處理主作物香蕉產量最高，且合於機械作業便於管理。故坡地蕉園暫以實施戀風草草帶較為經濟有效。 This experiment was carried out on a 13°(24%) slope banana plantation with clay loam soil at Chichi, Nantou Hsien from September 1970 to December 1975. The object is to find out that effects of soil conservation engineering methods compare with agronomic practices between the hillside ditches. Randomized complete block design was adopted with four replications and five treatments; namely, (A) drainage level terrace, (B) vegetative barrier with 2.5 meter spacing, (C) vegetative barrier with 5.0 meters spacing, (D) cover and mulching with Bahia grass, (E) clean cultivation plot as check. After six years, each soil conservation practice is highly effective than cleancultivated plot as check on the controlling of run-off and soil loss, the increasing of banana yield and the changing of soil physico-chemical properties. The results obtained are summarized as follows: (1) On the amount of run-off and soil loss, cover and mulching with Bahia grass is minimum, while the clean cultivation plot is maximum. The former has the least soil loss of 0.364 tons/ ha. within 4 years. (2) Vegetative barrier with 5.0 meters spacing has the highest fruit yield. Check plot the least. Cover and mulching wiht Bahia grass plot can also increase the yiedl totaling 12.80%. (3) On soil moisture during the period of dry season, the plots of cover and mulching with Bahia grass and clean cultivation give the lowest content. Drainage level terrace plot the highest. (4) Cover and mulching with Bahia grass plot has both the maximum infiltration rate and hydraulic conductivity. (5) As to the apparent and the real specific gravities, the range of changing is less among the various treatments. (6) Organic matter content and other chemical properties in the treatments are improved between the initial and the final periods except clean cultivation plot. (7) Considering the reduction of slope, vegetative barrier with spacing of 2.5 meters is greater than that of 5.0 meters. In general, cover and mulching with Bahia grass is highly effective in terms of erosion control and the improvement of soil properties. The most appropriate soil conservation method for slopeland banana platation is weeping love grass barrier with 2.5 meters spacing instead of drainage level terrace. In view of economy and the results as mentioned, the authors suggest that strip cover crop and mulching with Bahia grass or other agronomic practices be employed as well as weeping love grass barrier with 2.5 meter spacing.