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A perennial grain is a grain crop that lives and remains productive for two or more years. While many fruit, nut and forage crops are long-lived perennial plants, all major grain crops presently used in large-scale agriculture are annuals or short-lived perennials grown as annuals. Scientists from several nations have argued that perennial versions of today's grain crops could be developed and that these perennial grains could make grain agriculture more sustainable.〔〔〔 ==Rationale== The 2005 Synthesis Report of the United Nations’ Millennium Ecosystem Assessment program labeled agriculture the “largest threat to biodiversity and ecosystem function of any single human activity.”〔 Perennial grains could reduce this threat, according to the following logic: *Most agricultural land is devoted to the production of grain crops: cereal, oilseed, and legume crops occupy 75% of US and 69% of global croplands. These grains include such crops as wheat, rice, and maize; together they provide over 70% of human food calories.〔 *All these grain crops are currently annual plants which are generally planted into cultivated soil. *Frequent cultivation puts soil at risk of loss and degradation.〔 *This "central dilemma"〔 of agriculture in which current food production undermines the potential for future food production could be escaped by developing perennial grain crops that do not require tilling the soil each year. No-till technology enables short-lived (annual) crops to be grown with less intense tillage, but perennial plants provide the most protection for the soil.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「perennial grain」の詳細全文を読む スポンサード リンク
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