Herve Guibert, Cirad, Cra-CF, Recette principale 01 BP 715, Cotonou, Benin, Corinne Fesneau, Universite de Bourgogne, 6 boulevard Gabriel, Science de la Terre, Dijon, 21000, France, and Mathurin M’Biandoun, IRAD, Centre de Maroua, BP 15, Garoua, Cameroon.
The status of soils under cotton crops must be compared before and after a sufficiently long cropping period in order to detect variations that have occurred. Continuous monitoring of plots in research stations to determine such patterns is, however, long and costly. To overcome this problem, a study was carried out in 2004 in plots that had been monitored previously. Scientists, technicians and farmers who participated in the first assessment were also involved in the present study, so the plots could be accurately located. The second assessment was conducted using the same analytical techniques as those described in the first assessment. A database was compiled with data from 58 plots on ferruginous soils in the Bénoué cotton-growing area, with the interval between two assessments ranging from 4 to 21 years. The results presented here concern 27 plots. The study revealed that: (i) the soil organic matter contents had barely declined, (ii) the soil CEC had sharply decreased along with the N, K, Ca and Mg soil mineral contents, and (iii) this decline in mineral reserves paralleled the mineral deficiency of the crops. These hypotheses should be confirmed by processing the remaining collected data, but it was found that the characteristics of these especially fragile soils decreased, even though no impacts on production were detected, that these variations were not concomitant to a reduction in total soil organic matter, and that the decrease in mineral reserves is the most worrisome factor for the future of these cropping systems. These results were readily and cost-effectively obtained. The geographical coordinates of the fields in which soil samples were collected were unfortunately not determined, and the soil analysis results were not adequately stored. This calls for the construction of databases to pool raw research results that are accessible to everyone, and in this way research would fulfil its role of producing and providing public access to collected information.
Recorded presentation