Memoire en français, summary in English:
Agriculture plays a crucial role in the economy of developing countries, and constitutes the principal source of food, income and employment for their rural populations.
Several authors stated that the soil fertility degradation in farmer’s fields is the fundamental biophysics cause of the decrease of agricultural production per capita in Africa. This degradation is due to the lack of restitution of nutriments drawn by plants. In addition to the decrease in quantity of production, in many poor countries, the human consumption suffers from a lack of proteins.
However soya as a leguminous plant which can improve nitrogen fertility of the soil through the biological nitrogen fixation but also is one of these leguminous plants which is famous for its high proteins content.
Thus the purpose of this work is not only to evaluate the potential of soya to biologically fix atmospheric nitrogen in order to increase soil fertility but also to evaluate the response of soya through two varieties, to the inoculation of seeds by rhizobium, in order to increase the output of this culture. Moreover, this study should give response on the possibility of substituting the more expensive mineral fertilization by the inoculation of seeds.
The study was undertaken in Split-plot design with 3 replications with varieties as secondary factor (PK06 and SB24 varieties). Each main plot was divided into 3 subplots of 3mx3m carrying the level of nitrogen as main factor (Check, urea, inoculation).A quantity of 270 g of TSP and 108 g of KCL was applied to all subplots, at 10Cm from the planting line, the same day of planting. This design was installed in the two sites: in Murhesa, where soils are more or less provided with nutriments (Ferralsols on basaltic rocks and humus-bearing) and in Mushinga with a relatively poor soils (Ferralsols on metamorphic and sedimentary rocks).
For all the studied parameters the best results were recorded on Murhesa’s soil being, in addition to being a volcanic soil, less opposed to erosion problems compared to Mushinga’s soil. The various nitrogen levels however did not give significant differences for almost all of vegetative parameters except for the plant diameter for which plants receiving urea gave average better results compared to those which were inoculated and the check at Mushinga.
However the zero level of nitrogen (Check) gave the raised outputs to Murhesa, proving by there the uselessness of nitrogen addition in soils already equipped with nitrogen which would be a luxury for the plant. The best results of PK06 at Mushinga make it possible to understand the varietal response and the understanding of the behavior of various varieties.
MSc and Bcs thesis, internship reports