The Impact of Diatomite and Vermiculite Powder Ratios on the Properties of the Mixture and the Quality of Tobacco Pelleted Seeds

To improve the quality of tobacco pelleted seeds and meet the operational requirements of modern air-suction seeders, this study used diatomite (L) and vermiculite powder (M) as test materials. Elevenmixture formulations were designed based on mass ratio (namely L, L₉M_1, L₈M₂, L₇M₃, L₆M₄, L₅M₅, L₄M₆, L₃M₇, L₂M₈, L₁M₉, M). The differences in 10 powder indices, 4 pelleted seed indices, and 7 germination indices among these 11 formulations were analyzed, and the correlations between these indices were investigated. The results showed that diatomite had a larger particle size range, Carr index, porosity, Hausner ratio, and tapped density than vermiculite powder, while its span, apparent density and equilibrium moisture content were lower (p≤0.05). In the mixtures, as the proportion of vermiculite powder increased, the span and equilibrium moisture content increased significantly, while the other powder indicators exhibited multimodal trends. The cracking time of seeds pelletized with diatomite was significantly shorter than that with vermiculite powder, whereas the compressive strength showed the opposite trend (p≤0.05). In the mixtures, as the proportion of vermiculite powder increased, the thousand-seed mass, compressive strength and cracking time of the pelleted seeds increased, while the breakage rate decreased (p≤0.05). Significant positive or negative correlations were observed between the 10 powder indicators of the fillers and the 4 quality indicators of pelleted seeds, while no significant correlations were found with the other 6 germination indicators, except for seedling length (p≤0.05). Among the 11 formulations, L₁M₉ demonstrated superior performance in several powder properties, including span, Carr index, porosity, Hausner ratio, and water solubility. The L₁M₉ pelleted seeds exhibited a germination rate, compressive strength, and disintegration time that all complied with national standards. Moreover, they possessed a high thousand-grain mass and a low breakage rate, making them well-suited for use with air-suction seeders. Therefore, it is suggested that the combination of diatomite and vermiculite powder in a mass ratio of 1:9 be accelerated for pilot-scale trials and even promotion.