In order to study the effect of the composite substrate added with decomposed wheat straw on cucumber seedling cultivation, six kinds of substrate were obtained by compounding decomposed wheat straw, coconut bran and vermiculite in different proportions, with coconut bran∶vermiculite = 5∶5 (volume ratio) as the control and Jinzao 198 cucumber as the test material. By analyzing the phenotypic traits, biomass accumulation and physiological indexes of seedlings, and using principal component analysis for comprehensive evaluation, a suitable compound substrate formula was screened out. The results showed that: adding decomposed wheat straw was beneficial to the growth of cucumber seedlings, and low addition amount was better than medium and high addition amount. The seedling emergence rate of cucumber seedlings treated with T6（decomposed wheat straw∶ coconut bran∶ vermiculite = 1∶3∶5）was the highest, reaching 98.67%, which was 4.77% higher than that of the CK; the phenotypic traits such as stem diameter, hypocotyl length and maximum root length were the best; the biomass accumulation was the highest, and the seedling strength index was the highest, reached 0.15 and were 50% higher than control; Chlorophyll value, root activity, leaf soluble protein, and soluble sugar content were significantly higher than those of the CK，It increased by 6.68%, 41.70%, 6.69% and 15.38% respectively, and the activities of sucrose phosphate synthase, sucrose synthase, and nitrate reductase were significantly better than those of other treatments. The comprehensive ranking of different evaluation indicators for each treatment is: T6>T5>T3>T4>T2>T1>CK. In conclusion, T6 (decomposed wheat straw∶coconut bran∶vermiculite=1∶3∶5) treatment significantly promoted the growth of cucumber seedlings, and could be used as the best substrate formula for cucumber plug seedlings. This paper provides a theoretical reference for the use of rotted wheat straw in vegetable seedlings, thereby reducing the cost of factory seedlings and improving the quality of seedlings.

decomposed wheat straw  /  cucumber  /  plug seedling