Abstract
In semiarid regions, drought is the major threat to crop production, but climate change and variability often bring floods to the regions, forming seasonal wetlands causing damage to local, drought-adapted staple grains and, hence, low yields and food deficit. Introduction of the semiaquatic crop rice (Oryza spp.) to these semiarid wetlands could complement the dryland crop low yields and overcome the food shortage problem. A field experiment was carried out at the University of Namibia-Ogongo Campus during the 2016/2017 and 2017/2018 cropping seasons to assess the growth and yield of rice genotypes. Twelve short-duration rice genotypes, nine from the International Rice Research Institute (IRRI) and three locally grown upland NERICA genotypes, were used. Parametric analysis of variance was performed to test their effects on crop growth and yield characters. The results showed significant genotype by year interaction for days to heading, plant height, the number of tillers per m2, shoot biomass, the number of panicles per m2, 1000-grain weight, harvest index, and grain yield. The IRRI genotypes produced a higher number of tillers, shoot biomass, and grain yield than the NERICA ones, which were early maturing, were taller, and had higher 1000-grain weight across the years. Generally, most of the genotypes had lower grain yield and higher shoot biomass in the first year, due to the prevailing cool, rainy, and seemingly cloudy weather conditions associated with lower temperature and lower solar radiation. Grain yield was positively correlated with most characters but negatively correlated with the 1000-grain weight. These results demonstrate the yield superiority of IRRI genotypes over their early-maturing NERICA counterparts. However, further studies on morphological characters and drought tolerance of the IRRI genotypes are warranted to ascertain production sustainability under semiarid environments.
Highlights
Food deficit is a serious problem in the Sub-Saharan region, especially in the semiarid areas of the subcontinent
We evaluated growth and yield of short-duration rice genotypes in a field experiment conducted under seasonal wetland conditions during the 2016/17 and 2017/18 cropping seasons (December–April) at the University of Namibia-Ogongo Campus (17°41′S, 15°17′E, 1094 m altitude), north-central Namibia (Figure 1). is region is characterized by a semiarid climate with a mean temperature of >22°C [26] and annual mean rainfall ranging from 450 to 500 mm [5]. e campus lies in the Cuvelai Drainage Basin, originating in southern Angola. is basin is characterized by a natural, massive network of interconnected shallow pans locally called iishana and extensively interpolated deep water ponds called oondombe, which traverse huge areas of north-central Namibia before they converge to form an inland delta in the Etosha National Park (Figure 1)
Genotypic Performance. e main objective of the present study was to assess the growth and yield performance of shortduration rice genotypes under north-central Namibia’s seasonal wetland conditions. e results showed a significant effect of genotype by year interaction on the growth characters of the rice genotypes (Table 1). ese results seem to reflect high genotypic diversity, which is expressed through variable genotypic responses to the prevailing weather environmental conditions
Summary
Food deficit is a serious problem in the Sub-Saharan region, especially in the semiarid areas of the subcontinent. A semiarid Sub-Saharan country in southwestern Africa, faces a daunting challenge of food production to feed its growing population. E average annual rainfall ranges between 200 and 450 mm, and most of this rainfall is received in the country’s northern region, comprising the most densely populated subsistence farming communities [2]. Due to the relatively higher rainfall occurring in this region, compared with the rest of the country, most local farmers are involved in crop production, cultivating dryland traditional crops, mainly pearl millet (Pennisetum glaucum L.), sorghum (Sorghum bicolor M.), maize (Zea mays L.), and cowpea (Vigna unguiculata L.) [2, 5]. Rice (Oryza spp.), on the other hand, is mainly imported as a milled product, and the import volumes have been increasing annually. ese import trends are likely to continue for years as more food would be required to feed the growing population [6]
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