Urban agriculture is an important part of the food and nutrition security of many cities and is growing in importance, especially with social disruptions such as climate change and pandemics. Plant foods, in particular, provide bioactive compounds and other essential nutrients. Therefore, it is important to provide timely and useful research resources to horticultural sector and food-related industries that want to produce high-quality plant foods at low cost to meet the market demands of urban agriculture. This study focuses on up-to-date information on urban agriculture, the mechanisms of production of bioactive compounds in plant foods, and the main factors influencing the levels of bioactive compounds in plant foods. As a strategy to improve the bioactive compounds of plant foods in urban agriculture, the recent trends in urban agriculture were investigated according to four categories: ground-based uncontrolled or controlled agriculture and building-integrated uncontrolled or controlled agriculture. In ground-based urban agriculture, the application of short-term abiotic or biotic stresses, such as agronomic management practices, can significantly affect the bioactive compound levels in fruits and vegetables. On the other hand, in building-integrated urban agriculture, horticultural scientists have been interested in artificial lighting, cultivation medium, and water use efficiency to improve the level and composition of functional components of plants. The future trend of urban agriculture is expected to change from ground-based to building integration considering the sustainability of agriculture. Therefore, ongoing research on the growth and bioactive content improvement of plant foods using building-integrated agriculture is an important aspect for urban agriculture.

The quantity and quality of runoff from green roofs have so far been studied using an extensive vegetated roof (substrate depth > 150 mm). However, studies on various substrate depths and vegetation for runoff and phytoremediation in temperate and monsoon climates, where heavy rain is concentrated in a specific season, are limited. Therefore, the purpose of this study was to investigate combined effects of substrate depth and vegetation of an unfertilized green roof on runoff reduction and airborne pollutant purification based on rainfall intensity. A total of 21 plots were implemented on a roof top with three substrate depths (100, 200, and 400 mm), two vegetation s (vegetated or non-vegetated), and control (plot with standard frame only). The runoff reduction increased significantly (p < 0.05) with increasing substrate depth. Vegetated plots had a slightly higher runoff reduction than plots without vegetation. Compared to controls, turbidity and pH tended to increase regardless of vegetation or substrate depth, with the exception of electrical conductivity (EC). However, concentrations of heavy metals (Cu, Zn, Mn, and Cd) in the runoff of vegetated plots were all significantly (p < 0.05) lower than those of un-vegetated plots and controls. These results suggest that as the rainfall intensity increases, the depth of the substrate is more important than vegetation for runoff reduction. In addition, the vegetation can be an effective tool to neutralize acid rain to stabilize pH and effectively reduce EC and heavy metals in the runoff by remediating dissolved air pollutants from rainwater.

Soybean sprouts are one of the most inexpensive and nutritious food items that can be easily grown year-round. Several studies have been conducted to increase their yield and nutritional values. This study was carried out to examine the effects of Pu-erh tea extracts on the production and nutrients content of soybean sprouts. Soybean seeds were soaked in 1%, 2%, or 3% (w/v) tea extracts, or tap water, before keeping for sprout cultivation; the sprout samples were named PE-1, PE-2, PE-3, and the control, respectively. The sprout yields were increased by up to 17% in PE-2 and PE-3 than in the control. The vitamin C, total free amino acid, total mineral, total isoflavone, total polyphenol, and flavonoid contents as well as the antioxidant potentials of the tea extract-treated sprouts were higher than those of the control. The results indicated that pre-soaking soybean seeds in 2% Pu-erh tea extracts could offer an easy, inexpensive, and efficient way to improve the yield and nutritional value of soybean sprouts.

Agricultural hydrogels improve water retention in a variety of substrates. However, little is known about their impact on herb cultivation in rooftop farming. To identify the optimal substrate and hydrogel concentration for the growth and flowering of spearmint ( Mentha spicata ) in rooftop gardens, coir and perlite were mixed in three different ratios of 80% to 20% (v/v; referred to as C ₄ P ₁ ), 50% to 50% (C ₁ P ₁ ), or 20% to 80% (C ₁ P ₄ ). Hydrogels were added into different substrates at different concentrations including 0 (control), 0.25, 0.5, 1.0, or 2.0 kg⋅m ^–3 . Substrate composition significantly affected the growth ( P < 0.001) and flowering ( P < 0.05) properties of spearmint. The addition of hydrogels into substrates resulted in a significant ( P < 0.05) increase in growth parameters for spearmint during the dry season. However, plants grown in C ₄ P ₁ , which has the highest ratio of coir, displayed inferior growth and flowering compared with those of the other two substrates during the rainy season. Therefore, a perlite-based substrate, such as C ₁ P ₄ with added hydrogel, provides a suitable environment for the cultivation of spearmint in rooftop gardens regardless of seasonal rainfall patterns.