The purposes of this study were to preliminary built-up the abundance-deficiency index ( ADI) of soil available P (Olsen-P) (SAP) and determine the appropriate phosphorus application rates (APAR) of different available P abun-dance-deficiency level soil for alfalfa in the North of China. The method of regression equation between soil available nutrient content and relative yield of the treatment with complete nutrients except one, the improved scheme for the grading of soil a-vailable nutrients abundance-deficiency, and the new applied formula based on“nutrient balance and projected yield minus soil fertility yield” for determining the appropriate fertilizer application rates were employed. The results showed that the ADI of SAP in the Northeast Plain of China for the first to fifth and the 6~11th level were >26, 14~26, 7~14, 4~7, 2~4 and 0~2 mg/kg, respectively. The ADI of SAP in the Inner Mongolia Plateau of China for the first to eleventh level were>28, 16~28, 9 ~16, 5. 2 ~9, 3. 0 ~5. 2, 1. 7 ~3. 0, 1. 0 ~1. 7, 0. 6 ~1. 0, 0. 3 ~0. 6, 0. 2 ~0. 3 and 0~0. 2 mg/kg, respectively. The ADI of SAP in the Northwest Oasis of China for the first to fifth and the 6~11th level were >20, 12~20, 7~12, 4~7, 2. 4~4 and 0~2. 4 mg/kg, respectively. The ADI of SAP in the Loess Plateau of China for the first to fifth and the 6~11th level were >29, 15~29, 7~15, 4~7, 2~4 and 0~2 mg/kg, respectively. The ADI of SAP in the Huanghuaihai Plain of China for the first to third and the 4~11th level were >13, 4~13, 1~4 and 0~1 mg/kg, respectively. When the projected yield of alfalfa hay is 15 t/hm2 , the APAR for the first to eleventh level soil are 0, 45, 90, 135, 180, 225, 270, 315, 360, 405 and 450 kg/hm2 , respectively.%为了初步建立我国北方紫花苜蓿土壤有效磷( Olsen－P)丰缺指标，并确定不同丰缺级别土壤的适宜施磷量，采用土壤有效养分含量与缺素处理相对产量回归方程法、土壤有效养分丰缺分级改良方案和“养分平衡—地力差减法”确定适宜施肥量新应用公式，开展了本研究。结果表明，东北平原区第1~5和6~11级土壤有效磷丰缺指标依次为>26、14~26、7~14、4~7、2~4和0~2 mg/kg；内蒙古高原区第1~11级土壤有效磷丰缺指标依次为>28、16~28、9~16、5.2~9、3.0~5.2、1.7~3.0、1.0~1.7、0.6~1.0、0.3~0.6、0.2~0.3和0~0.2 mg/kg；西北荒漠绿洲区第1~5和6~11级土壤有效磷丰缺指标依次为>20、12~20、7~12、4~7、2.4~4和0~2.4 mg/kg；黄土高原区第1~5和6~11级土壤有效磷丰缺指标依次为>29、15~29、7~15、4~7、2~4和0~2 mg/kg；黄淮海平原区第1~3和4~11级土壤有效磷丰缺指标依次为>13、4~13、1~4和0~1 mg/kg。当紫花苜蓿干草目标产量为15 t/hm2时，第1~11级土壤的适宜施磷( P2 O5)量依次为0、45、90、135、180、225、270、315、360、405和450 kg/hm2。
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