[Suitable row spacing for mechanized cultivation of eggplant in solar greenhouse]

To facilitate mechanized tillage, transplanting and later management in a solar greenhouse, we evaluated the effects of four row spacing treatments: T₁ (large row spacing 150 cm; small row spacing 30 cm; plant spa-cing 44 cm; width of walkway 110 cm), T₂ (large row spacing 140 cm; small row spacing 40 cm; plant spacing 44 cm; width of walkway 100 cm), T₃ (large row spacing 130 cm; small row spacing 50 cm; plant spacing 44 cm; width of walkway 90 cm), and T₄ (large row spacing 120 cm; small row spacing 60 cm; plant spacing 44 cm; width of walkway 80 cm). A control treatment (CK) was included, with large row spacing 90 cm, small row spa-cing 70 cm, plant spacing 50 cm, and width of walkway 50 cm. We examined the effects of different row spacing configurations on photosynthetic efficiency and yield of eggplant in solar greenhouses, aiming to screen out the sui-table row spacing setting for mechanization suitability. The results showed that across T₁-T₄ treatments, leaf angle of middle leaves, chlorophyll a and chlorophyll b contents, net photosynthetic rate, dry matter accumulation, and yield first increased and then decreased with the increases of small row spacing. All these parameters, except for the middle leaf angle, peaked in treatment T₃. The petiole angle first decreased and then increased, reaching its lowest point in treatment T₂, while the canopy transmittance of direct solar radiation gradually increased. Yield was positively correlated with the indexes other than the leaf angle, and dry matter accumulation was highly correlated with the yield. At 90 days after transplanting (during the peak fruiting period), the chlorophyll a content in leaves was increased by 19.2%, 24.9%, 27.9%, and 17.2% in treatments T₁ through T₄, respectively. Chlorophyll b content was enhanced by 14.4%, 15.8%, 27.0%, and 0.9%. Net photosynthetic rate was improved by 4.7%, 15.5%, 17.0%, and 5.6%, while dry matter accumulation was increased by 1.9%, 4.9%, 4.9%, and 2.9%. Yield enhancements were 0.4%, 6.1%, 11.3%, and 10.9% for T₁ to T₄, respectively. For all these metrics, treatment T₃ exhibited the strongest effects. In addition, the walkway between the borders under this treatment was wider, which was convenient for agricultural machinery operation. In all, the T₃ treatment was not only beneficial for achieving mechanized cultivation of eggplants in solar greenhouses, but also can increase eggplant yield, making it the most suitable row spacing setting.