Received: 18-04-2018 / Accepted: 12-07-2018
The objectives of the study were to evaluate i) effect of ecological zones of fresh and brackish water on rice-shrimp cultivation systems, (ii) chemical characteristics of soil and water of the agro-ecological zones, and (iii) the efficiency of liming on rice growth and yield. Field experiments were conducted during August to December 2013 in Phuoc Long and Hong Dan, Bac Lieu province. Results showed that, after shrimp harvest, Phuoc Long planted rice crop in August when soil salt concentration was high (ECe: 8.0 mS/cm; ESP: 13.8%). Exchange cations in the soil decreased in the descending order: Mg2+>Na+>Ca2+>K+, corresponding to 8.0>3.0>1.5>1.0 meq/100 g, respectively. Due to salt accumulation in the soil in brackish water zone, ECe and ESP were at high levels during December (5,6 mS/cm and 7,8%, respectively), unfavourable for growth and yield of rice in comparison with fresh water zone at Hong Dan. Lime application to the salt-affected soil in Phuoc Long reduced salt damage to rice in terms of panicle number per square meter, filled grain rate, and higher grain yield (by 0.6 t ha-1) as compared to without liming. However, lime application to rice soil in fresh water zone at Hong Dan did not significantly increase the grain yield.