Soil Parameters Related to Crop Growth Variability in Western Niger, West Africa

Abstract

AbstractA study was carried out to determine soil morphological and chemical properties that influence short‐range variability in the growth of millet [Pennisetum glaucum (L.) R. Br.] in western Niger. Paired productive and adjacent nonproductive sites within millet fields were evaluated along transects in three soil‐geomorphic regions. Transects totaled >300 km in length. Mean depth to subsoil of productive sites ranged from 17.06 cm in the sand valley transect to 19.98 cm in the Dallol Bosso transect. These were different from the topsoil depths of the adjacent nonproductive sites within the respective transects, which ranged from 7.8 to 12.9 cm. Productive sites were located in microtopographic “high” positions relative to nonproductive sites. The mean relief differential between productive and nonproductive sites was 6.13 cm. Vesicular crusts 2 to 5 cm thick and exposed Bt horizon crusts (2.5YR 4/6) were mostly associated with nonproductive sites. The acidity parameters were highly intercorrelated in all transects. Mean pH of soils associated with productive growth of millet ranged from 5.8 to 6.3, compared with 5.4 to 6.0 in the nonproductive areas. Mean exchangeable acidity in the nonproductive sites ranged from 0.2 to 0.36 cmolc kg‐1, about three times higher than the mean in the productive areas. Bray‐1 P levels to a depth of 30 cm did not differ between paired sites in any of the transects. Microtopography was the most important factor influencing millet growth variability in western Niger because it directly influenced the factors related to crust formation and determined the depth to acidic, Al‐rich, P‐deficient subsoil that impeded millet growth and development.