Evaluation of Genetic Yield Gain: A Case of Lowland Rice Growing in Madagascar

Abstract

It was the first time in Sub-Saharan Africa, particularly in Madagascar, that a Genetic yield gain has been conducted among improved rice varieties during two successive cropping seasons (2014/2015 and 2015/2016) in the Middle West at the research station. It aims to analyze and to compare grain yields and their components for 12 varieties of rice distributed in Madagascar, by the Research Institutions since 1960 up to 2013. Given that water and nutrient management can be used to assess potential yields of rice, it is assumed that nutrient limitation and water stress are the main biophysical factor limiting the yield of irrigated rice grown outside of extreme temperatures. By a complete random block device with 3 repetitions, the 12 rice varieties are respectively subjected to the following three treatments such as T1: Optimal treatment in water and nutrients (target yield = potential yield), T2: Optimum nutrient treatment but sub-optimal in water, without additional irrigation, T3: Optimal treatment in water but sub-optimal in nutrients, closer to Malagasy farmers’ practices. Thus, for these years, the research released genetic yield gain under water stress and a high level of fertilization, with average yields of 3.5t/ha; against 3, 9t/ha at low level of fertilization and good water conditions. Finally, under good rice growing conditions (rich soil and water control), it is yielding around 4.5t/ha. This result may resolve not only socio-economic constraints with low input fertilizer but also climate change effects (drought) on rice cultivation.