Late flooding season results in low sediment levels, fewer aquatic food sources in rice fields in Mekong Delta

18 Nov 2021 Vietnamnet Source The Mekong Delta's flood season, commonly called "floating water season", caused by the rising level of the Mekong River in the rainy season, arrived in September, about one month late compared to other years.

Because of the low level of floodwaters, the amount of aquatic species has fallen by 30 per cent, according to farmers in Dong Thap Province.

The upstream provinces of Dong Thap and An Giang receive floodwater first, which runs from rivers into rice fields, bringing natural fishery resources and sediment to fields.

In An Giang Province's An Phu District, which is usually one of the delta's busiest fishing areas during flooding season, only a few boats are catching natural aquatic species in fields because of the low levels of floods.

Tran Van Gang, 68, in An Phu's Nhon Hoi Commune, said the number of natural fish, shrimp and other aquatic species in the fields remains small.

The floodwaters came late, so baby linh (Cirrhinus jullieni) fish, a speciality of the flooding season, are still living in rivers and are not arriving in the fields to live.

"There has been a loss of linh fish harvest in fields during this year's flood season," he said.

In An Phu District's Nhon Hoi, Phu Hoi, Vinh Hoi Dong communes, farmers are preparing tools to catch natural fish and other aquatic species, but the quantity is low.

Cao Xuan Dieu, secretary of the Nhon Hoi Commune's Party Committee, said fishing activities have not begun because floodwaters are still low.

In addition, because of COVID-19, people must strictly implement prevention measures and only go out when necessary.

The flood season is also the harvest season for điên điển (Sesbania sesban) flowers, a food speciality of the flood season. Điên điển trees grow along rivers, canals and fields, and their flowers are used to make dishes such as sour and sweet soup and fermented flower pickles.

Nguyen Thi Lai in An Giang's Chau Phu District said that điên điển trees bloom only once a year during the flooding season. In previous seasons, Lai and her neighbours got up at dawn and used small boats to travel to harvest điên điển flowers and sell them at a local market.

She was able to harvest three to five kilogrammes of điên điển flowers a day in previous years. However, this year Lai and her neighbours did not harvest the flowers because there were so few of them and they wanted to strictly follow pandemic prevention measures.

Fertilising fields

Besides bringing in natural aquatic species into rice fields, floodwaters also bring in sediment which fertilises fields.

Floodwaters also destroy disease pathogens and wild grasses in rice fields, helping farmers to lower production costs for the next rice crop.

In An Giang and Dong Thap provinces, many farmers do not grow the autumn – winter rice during the flooding season and instead let floodwaters flow into rice fields to fertilise the fields.

Phan Van Giau, from Tinh Bien District's Nhon Hung Commune in An Giang, said: "Every year after harvesting the summer – autumn rice, farmers here do not grow the autumn – winter rice and let the floodwaters flow to get the sediment."

The An Giang Department of Agriculture and Rural Development has instructed farmers who are not growing summer – autumn rice to let floodwaters run into the fields to get sediment, and destroy germs and wild grasses, so the fields will be fertilised for the 2021 – 22 winter – spring rice crop.

Nguyen Si Lam, director of the An Giang Department of Agriculture and Rural Development, said to avoid a shortage of irrigation water and an outbreak of brownplant hoppers, the main rice pest, the province will sow the winter – spring rice crop in three waves between November and December.

The delta is forecast to face early saltwater intrusion and drought in the 2021 – 22 dry season because of low floods this year.

Aquaculture

Farmers whose fields are submerged in floodwaters often breed aquatic species or grow other aquatic plants like water lilies or lotus in their fields to earn additional income during the flooding season.

They also breed a variety of fish such as linh fish, snakehead fish, or shrimp.

Huynh Van Kiem, who owns a 10ha rice field in Dong Thap Province's Hong Ngu District, said after harvesting the summer – autumn rice, he usually breeds snakehead fish in the field during the flooding season.

The profit is three to four times higher than from growing rice, he said.

Authorities in Dong Thap Province's upstream areas like Hong Ngu District and Hong Ngu City have instructed farmers on how to breed fish and shrimp during the flooding season.

Duong Phu Xuan, head of the Hong Ngu City Economic Bureau, said that because the amount of natural fishery resources from the flooding season has diminished, farmers in upstream areas can earn income from breeding fish and shrimp.

"The city plans to develop a community – based aquaculture model in rice fields after the summer – autumn rice crop," he said.

Under the model, farmers will let floodwaters flow into rice fields and breed aquatic species in the rice fields. This will help to protect fishery resources, clean rice fields of germs, and offer farmers income from community – based aquaculture.

Source:https://vietnamnet.vn/en/sci-tech-environment/late-flooding-season-results-in-low-sediment-levels-fewer-aquatic-food-sources-in-rice-fields-in-mekong-delta-792908.html