Performance of Rice Genotypes under Temporally Variable Wetland Salinity Conditions of a Semiarid Sub-Saharan Climatic Environment

Abstract

In semiarid regions, soil salinity, like drought, restricts crop productivity, causing food shortages among most inhabitants—the smallholder subsistence farmers. Seasonal wetlands formed in these regions during the rainy seasons could be utilised for rice (Oryza spp.) cultivation to increase food security, but rice is sensitive to salinity. Field and greenhouse-pot experiments were performed at the University of Namibia-Ogongo Campus, North-Central Namibia, to evaluate rice genotypes’ responses to seasonal wetland salinity. The field experiments assessed 16 rice genotypes for growth during the dry season and grain production during the rainy season, in saline and non-saline (control) seasonal wetlands. The saline-wetland salinity was predominantly NaCl; electrical conductivity levels increased from 2.8 dS m−1 (rainy season) to 34.3 dS m−1 (dry season), resulting in a 0–14% dry-season plant survival rate. The rainy-season wetland salinity decreased paddy yields in all rice genotypes; however, Pokkali produced the highest paddy and relative yields. The pot experiment assessed CG14 (salt-sensitive) and Pokkali (salt-tolerant) genotypes for growth using soils collected bi-monthly from the saline wetland. The rainy-season soil salinity reduced shoot growth in CG14 but did not affect growth in Pokkali, while the dry-season salinity killed both genotypes. The results of this study suggest the possibility of cultivating the salt-tolerant rice genotype, Pokkali, in the saline wetland during the rainy season due to salt dilution; however, the dry-season salinity levels would be detrimental to rice. More salinity-tolerance screening studies are warranted, in order to increase rice production and food security in Namibia and other flood-prone semiarid regions worldwide.