数十年来,在美国华盛顿苹果生产中,氮肥一直是基本的营养元素,在商品果园中苹果树对磷的反应研究的很少。最近,通过调查证明:在太平洋西北沿岸和其它低磷地区,苹果幼树对土壤磷的反应很敏感。许多土壤实验揭示了:在低有效磷(<10ppm)的果园中,树势衰弱且产 Nitrogen fertilizer has been a basic nutrient element in apple production in Washington for decades in the United States, and little is known about the reaction of apple trees to phosphorus in commercial orchards. Recently, surveys have shown that saplings are sensitive to soil phosphorus responses in the Pacific Northwest Coast and other low-phosphorus areas. Many soil experiments have revealed that in low-available-phosphorus (<10 ppm) orchards, tree vigor is weak and yields