Vol. 11, Issue 11 (2022)

Author(s):
Emily Alias and Deepa Thomas

Abstract:
Pokkali is a special rice farming system in coastal saline soils of Kerala. In these soils, higher sodium (Na) content and its interaction with other cations like potassium (K), calcium (Ca) and magnesium (Mg) within the plant become harmful for crop. Maintaining a low ratio of Na with other cations especially with K, is considered to be an yield determining and salt tolerance criterion in crops. There is a need to develop technologies in Pokkali rice for enhancing production and to have an edge in mitigating these stress conditions. A study was conducted at Rice Research Station, Vyttila with an objective to study the effect of the narrowing down of Na/K ratio in Pokkali rice by liming and foliar application of K. Treatments included soil application of different levels of lime (500 and 1000 kg/ha) or dolomite (800 and 1600 kg/ha) alone and these treatments followed by foliar spray of sulphate of potash (2% foliar spray at 20 and 40 days after transplanting). These treatments were compared with foliar spray of sulphate of potash alone and an absolute control (no amelioration, no foliar spray). The study showed that the sodium content in rice, Na/K ratio and Na/Ca ratio at flowering were negatively correlated with the grain yield. Among these ratios, higher Na/K ratio exhibited much more negative influence on the grain yield. A perusal of the data on correlation of Na/K ratio at different growth stages with yield also showed that treatments significantly influenced the plant Na/ K ratio at different stages of crop growth; Na/K ratio at flowering stage was found to be the most critical one. So maintaining a low Na/K ratio during the flowering stage benefitted the crop significantly. This indicated that amelioration and foliar spray of sulphate of potash in the field had significant influence in reducing the plant Na/ K ratio. Hence application of lime @1000 kg/ha and 2% foliar spray of sulphate of potash at 20 and 40 days after transplanting can be recommended for the increase in yield of Pokkali rice.