营养元素归还说 balance of nutritional element in soil: 土壤矿质营养元素平衡nutritional trace element: 营养痕量元素diminishing return theory: 报酬递减论; 收益递减论blade element theory: 叶片元素理论; 叶元理论blade-element theory: 叶片基元理论下载手机词典可随时随地查词查翻译