Variability in pearl millet (Pennisetum americanum) fields in semiarid West Africa

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Abstract
Extreme variability in pearl millet [Pennisetum americanum (L.) K. Schum] growth over very short (2–20 m) distances in the poorly buffered sandy soils of the semiarid West African Sahel poses major limitations to millet production and to field research efforts. A pot study using soils taken at 26 sites along a 15‐m transect from an unproductive to a productive region in a research field was conducted to determine the causes of variability in millet growth. Plant analyses showed that millet‐shoot weight 37 days after planting correlated best with shoot Al concentration (R2 = 0.81 for the 22 most unproductive sites). The critical concentration for Al toxicity in millet shoots was approximately 600 μg g−1. Millet growth also correlated well with shoot K concentration (R2 = 0.53). Poorly growing plants had deficient concentrations of P and K and potentially toxic levels of Mn. Low concentrations of plant P may be related to P fixation by soil Al.