Integrated Rice-Shrimp Farming in Coastal Areas

In practice, every year, the RSF system in LSAs and HSAs in the coastal MD consists of two phases (desalinization and salinization), with six sampling stages (stages 1–6) and two cultivation cycles (rice: July–December; shrimp: January–June) (Fig. 3).Fig. 3

Schematic of stages of RSF practice in LSAs and HSAs, Bac Lieu province.

Fig. 3In Bac Lieu, the average cultivation area of the model is 1.0–2.5 ha. A well-known local rice (Oryza sativa) variety, such as “one red bush,” and other modern varieties (OM5451, OM2017, HS182) that are salt tolerant are recommended to be grown in this area. The land is prepared after 2–3 rainfalls at the beginning of rainy season. Farmers are recommended to apply CaCO₃ or dolomite in combination with soil tilling. The lime mostly used in this research area was a commercial product made from limestone [11 ], with CaO and MgO contents of about 54%–57% and 17%–21%, respectively. The amount of liming material needed is 1.0–1.5 Mg ha⁻¹ [12 ]. During land preparation, the soil is submerged with rainwater or pumped canal water (CW; 2–3 days) to a depth of 10 cm above the field surface. Salt is leached by pumping water from the field to the canal, and the salt leaching cycle is performed three times. Farmers start sowing seed from August to September for long-growth period rice varieties, such as “a red bush” (duration 120 days), which is a local rice variety; or from September to October for short-growth period rice varieties.
Approximately 7–10 days before rice harvesting, water is drained from the field to facilitate harvesting. After rice harvesting, farmers dredge the mud in the ditch bottom. An amount of 0.9–1.3 mg ha⁻¹ of CaCO₃ is cast over its bottom and the pond is dried for 15–30 days. After that, the pond is filled with brackish tidewater, submerged in the soil for 5–7 days, and drained. This procedure is repeated about three times. The purpose of draining before the stocking of shrimp (Penaeus monodon) post-larvae is to remove the environmental contaminants that could be harmful to organisms in the soil.