1 22 CK 6.97 30.00 15.00 65 125 3. EXPERIMENTAL RESULTS AND ANALYSIS 3.1 Influence of Different Substrates on Crop Growth 3.1.1 Influence on emergence rate The pot-based cultivation experiment was initiated in early April 2024 within a greenhouse. The experiment utilized planting boxes measuring 50 cm (L) × 40 cm (W) × 28 cm (H). Pak choi seeds were procured from Tangshan Academy of Agricultural Sciences. During the growth period, the plants were regularly watered and managed under uniform cultivation conditions. Pak choi sprouts 3 to 4 days after sowing, and the emergence rate reaches its highest level in 6 to 7 days. The emergence rates of pak choi in different substrates are shown in Figure 1.Figure 1 indicates that pak choi is able to germinate in any substrate, with an average emergence rate of over 85% and equivalent to that of the CK. The emergence rate of R2, R5, and R8 is higher than that of the CK; the emergence rate of R1, R4, and R7 is slightly lower than that of the CK; the emergence rate of R3, R6, and R9 is close to that of the CK. This indicates that after adding a certain ratio of microbial fertilizer, the ratio of finegrained gangue and tailing coal slime is different, and the overall trend in emergence rate follows R2 > R3 > R1, R5 > R6 > R4, and R8 > R9 > R7. This suggests that the substrates exhibit optimal water retention and aeration properties when the fine-grained gangue is mixed with tailing coal slime in a 1:1 ratio. A high ratio of fine-grained gangue results in a weak water retention capacity, adversely affecting seed root development. A high ratio of tailing coal slime reduces substrate aeration, consequently decreasing the emergence rate. Figure 1 - Emergence rate of pak choi in different substrates It should be noted that in previous experiments, when the ratio of microbial fertilizer exceeded 15-20%, seedlings wilt and the emergence rate dropped significantly. Taking into account the price factor of microbial fertilizer, we have ultimately determined its maximum ratio as 10%. 3.1.2 Influence on growth performance of pak choi
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