有機資材利用之試驗研究現況與展望

Abstract

土壤有機質可改良土壤物理、化學及生物性，利於作物耕作管理，並為作物營養要素之貯藏庫，因此其含量一般被視為土壤肥力（特別是氮素肥力）之指標，許多研究結果顯示適當施用有機物可增加土壤有機質、改良土壤性質並增加土壤氮素礦化量，進而增加作物產量，而臺灣地處亞熱帶，高溫多溼，微生物活動力強，有機物分解迅速，故據調查一般耕地土壤有機質含量偏低，有44.8％土壤含量低於2.0％，因此為長期培育土壤生產力，即須設法維持或增加土壤有機質含量至一適當範圍。然而究竟什麼才是適當之土壤有機質含量範圍？又不同類有機物之適當投入量為何？則尚待研究。土壤有機質之積聚速率取決於有機物之投入速率與分解速率。有機物在水田之分解速率有別於旱田者。若干長期試驗結果顯示：稻田因浸水還原，有機物分解較慢，故在兩期稻作下，留在土壤中的根與莖基每公頃約有5~10噸，則土壤有機質含量即可維持不減，若另將地上物回歸土壤，則尚可增加土壤有機質含量；反之如以水旱或旱作輪作，則即使地上部作物殘株回歸土壤的乾物量每年每公頃在9噸左右（連地下部合計約18噸），土壤有機質仍逐年漸減。因此欲增加或維持本省土壤有機質含量，即需研究如何在不同之耕作系統下適量投入有機物。而臺灣地區每年所產生的農牧有機廢棄物數量龐大，包括作物殘株及禽畜糞等估計共有2,034萬噸，含有大量生質能源與植物養分，如能妥善循環利用，回歸土壤，不僅可協助解決環境污染問題，並有助於增進土壤生產力。有關有機物合理施用技術之研究課題包括有機物的利用方式（直接施用或做成堆肥）、經濟合理施用量及施用技術（包括有機物之經濟用量、養分釋放曲線、配方調整或配合化學肥料施用等）、長期施用對土壤肥力與作物生長之影響、及有機物施用之氮磷與重金屬污染評估等，期能建立適合本省氣候環境、耕作制度、作物種類之有機物合理施用技術，同時達到兼顧有機物施用的經濟效益與環境維護之目標。本篇將摘要討論若干有關試驗研究成果並提出未來應加強研究之方向。 Soil organic matter can improve soil physical, chemical and biological properties and thus is beneical to crop production. It also contains the essential elements for crops which can be released after microbial decomposition. Therefore soil organic matter content is usually recognized as an indicater of soil fertility status ( especially for soil nitrogen fertility). And in order to increase soil productivity, soil organic matter content should be increased or maitained at a certain level by applying organic materials. About 44.8% of the farm land in Taiwan has a soil organic matter content below 2.0%. Many experiments done in Taiwan showed that an approiate use of organic materials, such as crop residues, animal wastes, and composts, in combination with some proper amounts of chemical fertilizers can improve crop yield and quality. However inappropriate use of organic material can also caused a decline in crop yield and quality and cast doubts on ground water pollution. In addition, the application of organic fertilizers is quite costly. Therefore organic materials should only be recommended for farmers to use if it is economically feasible and environmentally sound. On the other hand, there are about 20 million tons of animal wastes and crop residues produced in 1994. Among them, about 2.4 million tons dry matter of animal wastes were produced, which contains considerable amount of nutrients. These animal wastes have to be composted or treated properly and the niutrients contained in them be recyled for crop production. To promote the use of these animal wastes by farmers, their sale prices should be kept as low as 2,000 NT dollars per ton and some handy application machine should be developed. In this paper, some research results in reation to the appropriate use of organic materials were reviewed and the perspective of future research activities was also discussed