The Nang Keo rice variety is a traditional seasonal rice that has been cultivated and preserved by local people for hundreds of years. The name Nang Keo, like other aromatic rice varieties such as Nang Huong, Nang Thom, Nang Tet, Nang Gao, is named after a maiden. Nang Keo is most widely grown in the natural rice-shrimp farming areas of Thanh Phu district, Ben Tre province. Rice in Thanh Phu district has even inspired poetry: "Golden rice of Thanh Phu, cassava of Thanh Phong". Due to its high salt tolerance, Nang Keo rice is well-suited to the rice-shrimp farming model in coastal areas where the land is flooded during high tide or subject to saltwater intrusion. This rice-shrimp farming model is becoming a smart farming method to adapt to climate change. To this day, the people of Thanh Phu still maintain their traditional ways of life, habits, cultural characteristics, and traditional farming methods for Nang Keo rice.
Thanh Phu rice is short and round in shape, with firm, uniform grains that are less prone to breakage. It has a light pink color and a mild aroma. The rice grains are 5.13 – 5.91 mm in length, with a length/width ratio of 2.10 – 2.40, and a gelatinization temperature above 74°C. Furthermore, the Amylose content in the rice ranges from 22.0 – 24.3%, the Protein content ranges from 9.43 – 12.10%, and the starch content is 72.20 – 75.30%. 

 Figure 1: Thanh Phu rice and cooked rice made from it 

The distinctive characteristics and quality of Thanh Phu rice are attributed to the specific conditions of the local land. The geographical area is relatively flat with many localized depressions. The average annual temperature is 27.3°C, the average total annual sunshine hours are 2,067, the average annual air humidity is 83%, and the diurnal temperature range is 11.4 – 14°C. These climatic features significantly impact the plant's photosynthesis process and the accumulation of dry matter in the rice grains, as well as prolonging the heading and nutrient accumulation stages of the rice plant. As a result, the protein content in the rice is relatively high, averaging 10.89%.
The soil in the geographical area is affected by saltwater intrusion due to high tides and is annually enriched by the Ham Luong and Co Chien rivers. The soil has a heavy texture, with salinity ranging from slight to moderate, an average pH (KCl) of 5.61, an average total P2O5 content of 0.31%, an average available P2O5 content of 0.18 mg/kg, an average total K2O content of 2.33%, an average OM (organic matter) content of 33.33%, and an average EC of 0.48 mS/cm. The irrigation water for Thanh Phu rice is also brackish, with a total dissolved solids (TDS) level ranging from 600 to 1,830 mg/l. Salinity affects the content of 2-acetyl-1-pyrroline (2AP) in rice grains, the main volatile compound responsible for rice aroma, leading to more fragrant rice grains. The P2O5 and K2O levels in Thanh Phu rice-growing soil provide adequate nutrition for rice plants to grow and develop in the early stages. Therefore, the soil does not require plowing, basal phosphate fertilizer application, lime for soil improvement, composted manure, or detoxification of alum to help the rice grow well from the beginning. 

 Figure 2: Thanh Phu rice field 

Besides natural factors, the farming and cultivation practices of the people of Thanh Phu also contribute to the unique characteristics and quality of Thanh Phu rice. Local farmers exclusively use the local Nang Keo rice variety to produce Thanh Phu rice. Furthermore, the rice-shrimp farming model is employed here, meaning that farmers only cultivate rice once a year, from July to December. During the remaining months, the rice fields are used as shrimp ponds. This crop rotation with shrimp farming allows for the decomposition of animal and plant waste, creating a porous humus layer on the cultivated soil. Also, due to the rice-shrimp rotation, local farmers must use fresh water to wash away the salinity through a system of water supply and drainage gates and expose the field for 3 to 7 days before planting.
Besides the rice-shrimp farming model, farmers in Thanh Phu also have unique pest and disease control techniques. When harmful insects appear while the rice plants are young, the field is flooded to submerge the tips of the rice plants for a few hours, then the water is drained (this is done 1-2 times per month following the rising tide). When the rice plants are larger, the water level is raised to near the base of the leaves. In addition, people also integrate fish farming in the rice fields or release ducklings into the fields 30 days after sowing to control pests and insects. This technique helps to improve the quality of the rice because the rice plants are completely healthy and not affected by harmful chemicals, resulting in higher quality rice grains compared to when pesticides are sprayed, as well as saving on pesticide costs and spraying labor.
In December, when the rice is over 85% mature, harvesting will begin. After harvesting, the rice will be threshed to extract the grains and sun-dried for three days. It will then be winnowed to clean it and stored in dry places indoors to prevent termites and mold. The rice should only be milled right before use or commercial sale to maintain its quality and nutritional value.
The geographical area for producing Thanh Phu rice consists of the communes of An Nhon, An Dien, Giao Thanh, Thanh Phong, An Thanh, An Qui, and My An, belonging to Thanh Phu district, Ben Tre province. 

Source: Bảo hộ chỉ dẫn địa lý "Thạnh Phú" cho sản phẩm gạo 
Translator: Nguyễn Hải Phong