Ly Son, about 17 nautical miles off the Quang Ngai coast, was formed by volcanic eruptions. Weathered lava has created mineral-rich basalt soil well suited to crops, particularly garlic and onions.
Farmers grow one garlic crop and three onion crops each year. On steep land near the island's extinct volcanoes, they have carved terraces into the slopes for cultivation.
The terraces are bordered by walls made from volcanic rocks, which help prevent soil erosion, retain water and shield crops from strong sea winds. They have also become a distinctive feature of the island's landscape.
Nguyen Van Binh owns a 400-square-metre terraced plot inherited from his family. Over the years, he has reinforced its volcanic-rock boundaries to protect the soil and crops.
The rocks are typically stacked 20-40 centimetres high to divide plots, while some farmers build walls 0.5-1 metre high as windbreaks.
"The land near the extinct volcano is steep, so we need terraces to keep the soil in place. Volcanic rocks are used for the boundaries, and some farmers build much higher walls to block winds from the sea," Binh said.
Local resident Dang Thi Ly said farmers began expanding garlic, onion and other crop cultivation around 40-50 years ago. Farming initially concentrated on flat land before spreading to steeper areas near hills and mountains.
Terraces became necessary on the slopes, with volcanic rocks used to retain soil and water. The higher stone walls also reduce the need for protective netting against strong winds.
Ly Son has about 300 hectares of agricultural land, part of which has been converted into terraces near hills and mountains, according to local economic officials.
Garlic is the island's main agricultural product and is prized for its quality, which is attributed to Ly Son's distinctive soil conditions. However, fluctuating garlic prices have caused concern among farmers in recent years.