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Soil nutrient deficiency and rainfall variability impair the production of sorghum (Sorghum bicolor (L). Moench) in Sudano-Sahelian zone. The aim is to study the environmental factors that can determine the effect of fertilizer application on sorghum grain yield and to formulate tailored fertilization strategies according to sorghum varieties (hybrid and open pollinated improved varieties) and environmental context. Field experiments were conducted during the 2015 and 2016 growing seasons in Nioro du Rip and in Sinthiou Mal&egrave, me (Senegal). In a randomized complete block design arranged in a split-plot with four replications, three factors were tested: sorghum genotype (G: Fadda, Faourou, Soumalemba and Soumba with different cycle lengths), environment (E: irrigation and rainfed, different soil types and fertility levels), and fertilization management (M: five different combinations of application dose and application time) including T1 = no fertilizer applied, T2 (recommended practice, 100%) = 150 kg/ha of NPK (15-15-15) at emergence + 50 Kg/ha of urea (46%) at tillering + 50 kg/ha of urea at stem extension, T3 = 50% T2, T4 (100% delay) = 150 kg/ha of NPK +50 kg/ha of urea at stem extension +50 kg/ha of urea at heading, T5 = 50% T4. Results showed that: (i) in most environments, stressed plants under late application treatments (T4 and T5) recovered biomass once the fertilizer was applied (ii), grain yield with T5 was higher than with T4 under well-watered conditions (sufficient and well distributed rainfall and eventual complementary irrigations), (iii) Fadda, a hybrid, responded differently to fertilization than the other varieties only for biomass production, (iv) late fertilizer application treatment (T4) gave higher grain yield than the recommended practice (T2) in the environment with low yield potential, and (v) long cycle duration genotypes benefited better from late fertilization compared to short cycle duration genotypes. This study showed that under Sudano-Sahelian conditions late fertilization of sorghum can be beneficial to grain yield if the rainy season has a slow start, depending on sorghum genotypes (i.e., cycle length), and on the initial N content of the soil.

Introducing sorghum (Sorghum bicolor L. Moench) genotypes into new environments is necessary for expanding the production of food and fuel, but these efforts are complicated by significant genotype &times, environment interactions that can reduce their effectiveness. This study set out to thoroughly analyze genotype &times, environment interactions and assess trade-offs between the agronomic performance and the stability of grain and biomass yields of ten contrasting genotypes under Sudano-Sahelian conditions. Experiments were carried out in a randomized complete block design with four replicates. They were conducted from 2013 to 2016 in Bambey, Sinthiou Malem and Nioro du Rip in Senegal. The joint analysis of variance revealed a highly significant effect (p &lt, 0.0001) of genotypes (G), environments (E) and G &times, E interaction. Most genotypes showed specific adaptations. The best grain yields were obtained by the Nieleni and Fadda hybrids, while the improved varieties IS15401 and SK5912 were best for biomass production. An Additive Main effect and Multiplicative Interaction (AMMI) analysis showed that good grain yields were associated with environments having good soil fertility and good rainfall, while biomass yields were more influenced by the sowing date and rainfall. Similarly, we were able to confirm for our 10 sorghum genotypes that yield stability was generally associated with low performance, except for the Nieleni and Fadda hybrids, which performed well for grain and biomass production regardless of the environment. The Senegalese control genotype, 621B, showed particular susceptibility to growing conditions (soil), but remained very productive (more than 3 tons per hectare) under good agro-pedological conditions. These results lead us to recommend the Fadda and Nieleni hybrids for the entire study region, while 621B can also be recommended, but only for highly specific environments with good soils.