This study aimed to explore companion planting to improve vegetable productivity on extensive green roofs through urban agriculture with limited substrate depth. From May to July 2021, the study conducted on the rooftop to evaluate the effects of marigold (Tagetes patula) planting ratio on the growth and pest control of cabbage (Brassica campestris). The experiment plot measured 1 m in width × 1 m in length × 0.25 m in height and 0.2 m in substrate depth. Fifteen plots were planted in varying proportions of cabbage and marigold for three repetitions per treatment: cabbage control (CC), 2:1(C2M1), 1:1(C1M1), 1:2(C1M2), and marigold control (MC). We found that companion planting marigolds with cabbage significantly increased cabbage growth and reduced pest infestation. The study revealed that C1M1, when cabbage and marigold have the same proportion, is an efficient companion planting ratio. Companion planting, in which non-crop vegetation manages pests and increases crop productivity, improves natural pest control and preserves biodiversity on rooftop urban agriculture.

This study aimed to evaluate the growth of Cichorium intybus, Brassica juncea, and Lactuca sativa at varying seed ratios, and to suggest an efficient management plan for sustainable indoor agriculture systems. It was treated with mixed sowing as follows: 30 chicory seeds (chicory alone: CC), 22 chicory seeds + 8 lettuce seeds (C3L1), 20 chicory seeds + 10 lettuce seeds (C2L1), 15 chicory seeds + 15 lettuce seeds (C1L1) as intraspecies, and 30 mustard seeds (mustard alone: MC), 22 mustard seeds + 8 lettuce seeds (M3L1), 20 mustard seeds + 10 lettuce seeds (M2L1), 15 mustard seeds + 15 lettuce seeds (M1L1) as interspecies. The study identified the competitive response in seed germination between Cichorium intybus and Lactuca sativa, and in the C3L1 experimental group, Lactuca sativa had the highest leaf length, root length, chlorophyll content, and fresh weight. Therefore, the higher the ratio of Cichorium intybus, the higher the growth and productivity of Lactuca sativa; however, higher the ratio of Lactuca sativa, the lower the growth of Cichorium intybus. Furthermore, the nitrogen and potassium content in the substrate was the highest in the C3L1 experimental grorp which had the highest seeding rate of the Cichorium intybus. Comparing the groups Brassica juncea and Lactuca sativa, the higher the seeding ratio of Lactuca sativa, the higher the growth and productivity of Brassica juncea. Therefore, a companion seeding of Brassica juncea and Lactuca sativa is beneficial; this could be effective in having a high seeding ratio of Lactuca sativa.