美国是世界上农业发达国家之一，它的农业相关产业相当发达。围绕着农业有一个庞大的关联产业群，被称为“食品．纤维体系”，它是国民经济中第一大产业，它的兴衰对美国整个经济、出口和就业形势影响极大。虽然美国农业产值占国民生产总值的比重很小，直接从事农业生产的人口? The United States is one of the developed countries in the world in agriculture. Its agricultural-related industries are quite developed. Around the agriculture has a huge associated industry group, known as the “food fiber system”, which is the largest industry in the national economy, its rise and fall of the United States the entire economy, exports and employment situation greatly affected. Although the proportion of U.S. agricultural output in the gross national product is very small, is the population directly engaged in agricultural production?