为了解决过量施肥、盲目施肥、肥料利用率偏低等问题，本文通过大量的田间肥料试验，研究施肥指标体系，旨在更好地指导当地农民科学施肥。本文根据“3414”田间试验结果，将土壤养分含量水平划分为“丰富”、“中等”和“缺乏”3个等级，建立莆田地区甘薯土壤速效氮磷钾丰缺指标。结果表明，与甘薯相对产量75%~90%相对应的土壤碱解氮、有效磷和速效钾的丰缺指标临界值分别为85~128 mg/kg、10~24 mg/kg和42~115 mg/kg。通过肥料效应函数计算出的各试验点的推荐施肥量与相对应的土壤有效氮磷钾含量测试值之间呈指数回归关系，由回归方程得出，中等肥力水平下的推荐施氮量范围为114~168 kg/hm2，推荐施磷量范围为51-62 kg/hm2，推荐施钾量范围为159~323 kg/hm2。

Because of excessive fertilization，blind fertilization and low fertilizer use efficiency，the study of soil test and formula fertilization index system on Sweet Potato was carried out through a lot of field experiment of fertilizer to guide farmers better for scientific fertilization.This paper illustrated a system, based on the “3414” field tests, that divided soil nutrient content into sufficiency, medium and deficiency grades and established indices to show the degree of sufficiency or deficiency on available N, P and K in soil for sweet potato in Putian. The results indicated that the critical value of sufficiency and deficiency for soil alkali-hydrolyzable N, Olsen-P and available K were 85-128 mg/kg, 10-24 mg/kg and 42-115 mg/kg, corresponding to 75%-90% relative yield of the sweet potato. The recommended fertilizer amount from the fertilizer effect function and the soil NPK test values were exponential regression relation. Obtained from the regression equation, the recommended fertilizer amount of NPK were 114-168 kg/hm2, 51-62 kg/hm2 and 159-323 kg/hm2 under the medium fertility level.