Vol.:(0123456789) 1 3 International Journal of Plant Production https://doi.org/10.1007/s42106-019-00082-4 RESEARCH Water Productivity of Selected Sorghum Genotypes Under Rainfed Conditions Sandile T. Hadebe 1,2  · Tafadzwanashe Mabhaudhi 2  · Albert T. Modi 2 Received: 14 June 2019 / Accepted: 14 November 2019 © Springer Nature Switzerland AG 2019 Abstract Water productivity (WP) is becoming a key issue in understanding the relationship between water availability and rainfed sorghum (Sorghum bicolor L. Moench) yields in agricultural systems across sub–Saharan Africa. The objective of this study was to determine water productivity of three sorghum genotypes under different environmental conditions. Three sorghum genotypes, a hybrid (PAN8816), a commercial open-pollinated variety (Macia) and a landrace (Ujiba) were planted at two sites (Ukulinga and Mbumbulu) in South Africa during 2013/2014 and 2014/2015. High clay content in Mbumbulu lowered plant available water in the soil compared to Ukulinga. Sorghum adapted to low water availability by significantly (P < 0.05) lowering plant growth (green leaf number, plant height and canopy cover), crop physiology (chlorophyll content index and stomatal conductance), biomass and grain yield. Ujiba and PAN8816 genotypes hastened phenological development, whilst Macia delayed phenological development in response to low water availability. Total and grain WP were lower at Mbumbulu (14.93 and 7.49 kg/ha/mm) relative to Ukulinga (21.49 and 11.01 kg/ha/mm), respectively. Results showed that Macia had significantly higher (P < 0.05) WP (10.51 kg/ha/mm) relative to PAN8816 (9.34 kg/ha/mm) and Ujiba (7.90 kg/ha/mm). Lack of significant genotypic differences in grain WP highlights that all three genotypes are equally suitable for production under sub–optimal and dryland conditions. Keywords Water productivity · Water stress · Sorghum · Water use characteristics · Physiology Introduction Sub–Saharan Africa (SSA) faces twin challenges of water scarcity and food insecurity and these challenges are pro- jected to increase. Within the region, rainfed agriculture constitutes more than 95% of agricultural land use (Singh et al. 2011), making water availability the single most impor- tant factor in crop production. Neither of these challenges can be addressed in isolation (Postel 2003; Rosegrant et al. 2009). Strategies to produce ‘more food per drop’ (Molden et al. 2010) have been considered in a variety of ways. These have included identifying areas of water availability, water stress (Brauman et al. 2013), impacts of water use and pro- jections of future water scarcity (Ringler et al. 2010; Mur- ray et al. 2012). Any improvement in crop water productiv- ity will have a positive effect on either food production or water savings (Brauman et al. 2013). Therefore, strategies to increase food productivity while conserving water have become increasingly important (Giovannucci et al. 2012). Among these strategies is selection of drought and heat tolerant crops, and screening of genotypes for high water productivity (WP). Drought stress is one of the most limiting factors for cereal crop yield. Drought and heat tolerance make sorghum unique among major cereal crops, suited for cultivation as staple food in arid agro-ecological regions of SSA (Hadebe et al. 2017). It is the second most cultivated cereal crop in SSA and ranks first in the semi–arid Sahel (FAOSTAT 2013). Although sorghum originated in SSA, where com- paratively striking drought tolerance and superior WP have developed in the species, there is a need to harness these traits to positively contribute to food production, especially * Sandile T. Hadebe shadebe@ufh.ac.za 1 Department of Agronomy, Faculty of Science and Agriculture, University of Fort Hare, P. Bag X1314, Alice 5700, South Africa 2 Crop Science, School of Agricultural, Earth and Environmental Sciences, University of KwaZulu–Natal, Private Bag X01, Scottsville, 3209 Pietermaritzburg, South Africa