【Objective】The aims of this work were to determine 1) whether reduced rates of chemical fertilizer coupled with PGPM inoculants (Trichoderma biofertilizer) would produce cucumber yield and quality equivalent to those obtained using full rates of chemical fertilizer and 2) how this type of fertilization affects the soil fertility of a continuous cropping system. 【Method】Pot trials were conducted 4 times with a reduced application of chemical fertilizer (75% of the recommended application) plus Trichoderma-enriched biofertilizer (BF) or organic fertilizer (OF), with 100% of the recommended chemical fertilizer (CF) as the control. 【Result】The results showed that supplementing 75% of the idiomatic fertilizer with TrichodermaSQR-T037 biofertilizer (BF) produced yield that was statistically equivalent to or higher than the 100% chemical fertilizer (CF) and increased by >21% of yield compared to the OF treatment. This result was consistent across in our previous field experiments, which also indicates that only biofertilizer could be a viable supplementary strategy of fertilizer for maintaining or increasing cucumber yield. Reduced chemical fertilization, both of the BF and OF treatments, resulted in a higher Vitamin C (2%~23% and 35%~54%, respectively) contents in the BF and OF treatments but a lower (32%~46%) accumulation of NO3- in the cucumber fruits compared than those of the control (CF), suggesting that replacing 25% of the chemical fertilizer rates with (bio) organic fertilizer could significantly increase cucumber fruit quality. The application of SQR-T037 biofertilizer (BF) significantly (p<0.05) increased cucumber rhizospheric nutrient availability. Specifically, the highest contents of available P were more frequently observed in the BF treatment. Moreover, the BF treatment maintained at a higher level of available K compared with that of the CF and OF treatments. Also, the BF treatment significantly increased the population of soil microflora, including bacteria and Trichoderma, maintaining the population of actinomycetes, but with the reduced abundance of fungi, compared with the CF treatment. Based on the explanations known in other researches, the relationship between soil nutrients and microflora in this study may be explained as follows: plant growth might initially be improved by enhanced root growth, which occurs in response to a powerful plant-growth-promoting fungus, T.harzianum SQR-T037, as reported in our previous study. Then, better root growth influences soil microbes via the supply of additional root exudates or rhizodeposition, and soil microbes, in turn, alter plant performance through higher microbial abundance and more frequent interactions resulting in more available nutrients. This process continues in a cycle. More bio-available nutrients promote better root growth, which facilitates more microbial colonization in the rhizosphere, and ultimately results in greater nutrient uptake by the inoculated plants. 【Conclusion】The results of this study imply that the excessive use of expensive chemical fertilizer can be significantly avoided without compromising yield (at least in cucumbers) through the application of a Trichoderma -enriched biofertilizer. Additionally, the use of Trichoderma-enriched biofertilizer with lower fertilizer application resulted in enhanced fruit quality and an improvement in soil fertility and the microbial environment. Therefore, biofertilizer such as this could be used in combination with the appropriate rates of chemical fertilizer and should be applied over a long-term period as a component of integrated nutrient management strategies to obtain maximum benefits in terms of the yield, sustainable use of soil and fertilizer savings.