Abstract:The effects of biochar combined with fertilizer on cucumber yield and fertilizer use efficiency were investigated by a field experiment in order to provide a scientific basis for the improvement of fertilizer use efficiency and cucumber production. The field experiments were carried on the fluvo-aquic soil in Rugao city of Jiangsu Province, in which three fertilization levels were designed:1) traditional fertilization (F), 2) reduce 10% fertilization (F-10%), and 3) reduce 20% fertilization (F-20%). For each fertilization level, six biochar application rates were setup (0, 5, 10, 20, 30 and 40 t/hm2, designated as CK, C1, C2, C3, C4 and C5, respectively), with CK and CF (no biochar and no fertilization) as control. The results showed that, compared with CK at all fertilization levels, biochar treatments significantly increased cucumber yield, fertilizer use efficiency and related indicators (P<0.05). At F fertilization level, cucumber yield and N, P and K fertilizer use efficiencies in C5 treatments were 27.60 t/hm2, 23.75%, 3.62%, and 24.85%, respectively, which increased by 59.67%, 337.44%, 177.94% and 120.69% compared with CK; At F-10% fertilization level, compared to CK, cucumber yield and N, P and K fertilizer use efficiencies in C5 treatments increased by 73.88%, 163.82%, 234.33% and 183.24%, respectively. At F-20% fertilization level, compared with CK, cucumber yield and N, P and K fertilizer use efficiencies in C5 treatments increased by 82.10%, 148.73%, 246.46% and 215.66%, respectively. In the same biochar rate treatments, cucumber yield was not reduced in C2, C3, C4 and C5 treatments, but the fertilizer use efficiency was significantly increased, which reached the highest at F-20% fertilization level, compared with F fertilization level, N fertilizer use efficiencies in CK, C1, C2, C3, C4 and C5 treatments increased by 135.42%, 145.96%, 116.94%, 70.47%, 63.33% and 33.86% respectively, P fertilizer use efficiencies increased by 69.26%, 57.31%, 59.78%, 27.90%, 67.91% and 110.99%, respectively, K fertilizer use efficiencies increased by 27.90%, 99.55%, 84.75%, 62.97%, 60.91% and 82.94%, respectively. This study proves further biochar combined with fertilizer is an effective way to alleviate the obstacles of continuous cropping of cucumber.