耕作方式對南亞地區及臺灣稻麥輪作系統小麥產量及其成本評估

Abstract

稻麥輪作是南亞地區重要糧食生產栽培系統，種植小麥前的耕作模式可分整地、低整地與不整地，透過改變小麥播種前的耕作方式，可降低小麥延遲播種造成直接或間接對產量的影響，其中不整地雖可減少小麥田區準備的時間而不至於延後播種，但可能因土壤結構不利小麥根系生長造成減產。為了解決整地可能造成晚播的原因，較整地減少耕犁次數的低整地耕作可能是較為可行的替代方式，除了減少因多次耕犁而影響小麥播種外，低整地使土壤結構較為鬆散而具有高的水分滲透性，有助於小麥根系發展及截取水分，促進小麥生長發育，同時具較高的氮素利用效率，皆有助提升穀粒產量。臺灣小麥耕作方式有別於印度地區稻麥輪作，屬更集約的水稻－水稻－小麥輪作系統，耕作方式可分不整地撒播(no-till/broadcast sowing)、低整地撒播(reduced tillage/broadcast sowing)、低整地條播(reduced tillage/strip till)等三種，依據近年來於小麥主要產地調查得知，每公頃平均產量以低整地條播3,787 kg最高，較不整地撒播增產23.7%，造成產量差異主要係因低整地條播單位面積穗數顯著高於其他兩種。分析上述三種小麥播種方式之投入成本，結果顯示，雖然整地條播投入耕作成本較不整地撒播高，但因其產量最高，扣除投入耕作成本外仍有最佳之收益，應可推薦作為農民及農企業栽培管理的參考，將有助於提升臺灣小麥的產業競爭力及增進農民收益。 Rice-wheat rotation is an essential cropping system in southern Asia. Preparation prior to wheat sowing can be divided into tillage, reduced tillage, and no-tillage. Changing the tillage method alleviates the direct and indirect effects of delayed sowing on crop yields. In particular, no-tillage can reduce the preparation time and therefore avoid delayed sowing; however, this method leads to soil structure unconducive to wheat growths and yield losses. To address problems concerning delayed sowing due to tillage, reduced tillage that lowers the number of ploughing has been adopted as a viable alternative. This method creates loose soil structure with high water permeability, thereby facilitates the development and water acquisition of wheat roots. Accordingly, it is conducive to wheat growth, engenders high nitrogen utilization rates, and improves crop yields. Wheat cropping in Taiwan differs from that in India in that Taiwanese farmers generally adopt a rice- rice-wheat rotation system, the cultivation methods of which are divided into no-tillage with broadcast sowing, reduced tillage with broadcast sowing, and reduced tillage with strip till. Recent surveys on main wheat production regions in Taiwan have reported that reduced tillage with strip till leads to the highest mean yield at 3,787 kg per hectare, which is 23.7% higher than that of no-tillage with broadcast sowing. The difference in yields is mainly attributable to the notably higher panicle number per unit area of reduced tillage with strip till compared with other tillage methods. This study analyzed the costs of the three cultivation methods. The results indicate that despite the higher cost of reduced tillage with strip till compared with other methods, it leads to the highest yield and is therefore the most cost-effective after the cultivation cost is accounted for. This study can serve as a reference for farmers and agricultural businesses to manage their cultivation, helping the Taiwanese wheat industry improve its competitiveness and profits.