Potassium Nutrition in Rice (Oryza sativa L.) for Higher Yield with Lower Sodium Uptake under Saline Conditions of Central Vietnam

Potassium (K) is an essential macronutrient, improves rice yield and contributes to salt stress tolerance. This study determined the best potassium (K) application level on yield formation and the saline resistance capability of rice under salinity field conditions of central Vietnam.

Experiments were comprised of five K fertilizer application rates (0, 25, 50, 75 and 100 kg K₂O/ha) and two rice varieties, viz, OM8104 and MNR3 for two growing seasons of 2021 and 2022. All treatments were arranged in a split-plot design with 3 replicates in Duy Vinh commune, Duy Xuyen district, Quang Nam province.

Potassium application affected the number of panicles per unit area, filled grain per panicle and actual grain yield of both rice varieties in both seasons under saline condition. Application of 50 kg K₂O/ha reduced the soil salinity over the monitoring periods compared to the other K rates. EC values of soil were significantly higher during the hot season than the wet season showing high temperature effects. Application of 50 kg K₂O/ha also accumulated maximum dry matter at different crop stages and produced the highest rice yield with 7.57 and 5.25 tons/ha for OM8104 and 7.35 and 5.18 tons/ha for MNR3 in both wet and hot seasons respectively. The harvest index could not affect significantly by K application irrespective of seasons and varieties. These increases in actual grain yields using 50 kg K₂O/ha were attributed to increased filled grains per panicle, accumulation of high K⁺ content and K⁺/Na⁺ ratios in rice varieties in both seasons under saline field condition.