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Effect of Leucaena leucocephala, Poultry Manure or Cattle Manure on Maize Productivity on Feralitic Soil "terre de barre" in South Benin. Our work has consisted on the study of post-effect of Leucaen's prunings and poultry manure buried last year and also on the study of the direct effect of cattle manure and its interaction with Leucaen's pruning on maize productivity on feralitic soil "terre de barre". - The mixture of Leucaen's prunings and poultry manure had positive post-effect giving a yield of fresh ears and grains significantly higher (9 %) to the reference and other treatments in the plots over the alley. - The supply of 5 t/ha of cattle manure appears insufficient. On the other hand the mixture of Leucaen's prunings and cattle manure gave the best results related to the soil's properties such as organic matter's content or total exchange capacity of the soil and also concerning the yields. In this case we notice that ail the results are significantly higher to the other treatments. These results emphasize the importance of a supply of organic matter's to the soil thereby fertilizing it in humus and mineral elements.

Study of the backward effect of the burying of different organic substances with a view to the improvement of degraded ferruginous soils. With the help of a se ries of incubation in vitro, we have proved, the weak of a peat and the "starter" effect of poultry droppings mixed with this peat. Trials in the open fields allowed us to study the interaction between peat and other substances biologically more active namely poultry droppings, groundnut-tops and horse manure. The first year of the experimentation, the results showed the depressive action of the peat on account of the increase of the reorganization of nitrogen andphosphorous. Nevertheless, the results of the following rainy season (1987) (Study of backward effect) show the disappearance of the depressive effect of the peat. As a matter of tact we have noticed no important difference between the treatments enriched by only falling substances (droppings and tops) and those enriched by a mixture (peat x tops). The results of the 1988 rainy season put the stress on the lasting quality of the residual effect of the peat, because the yield of the treatment (B) enriched only by peat is placed at the same level as the yield after the contribution of groundnut-tops and it is significantly superior at the 5 % level to that of poultry droppings.

The influence of organic and calcareous amendments on yield of groundnut produced on acid degrated soils, in Senegal. Trials were carried out during the 1984 and 1985 seasons to determine the influence of organic matter and liming on low feriility acid soils using groundnuts as an indicator. Results indicated that groundnuts have a wide tolerance to variation in pH. Horse manure applied in 1984 had a significant influence on yield, reduced the rate of plant mortality, and had a positive residual effect in 1985. Peat mixed with either manure or commercial fertilizer increased yield, but to a lesser extent than manure alone because of its specific characteristics however, further testing of these treatments is under way.

Study of the dynamic of organic matter (O.M.) in saline soil. Using "in vitro" experiments, we studied the influence of salinity on the evolution and the transferts of humified compounds obtained from glucose and straw labelled with 14C. The intensity of these mechanisms were examined in different clayed horizons with increasing salinity contents. During incubation experiments parformed under controlled conditions, we found a negative correlation between salinity infered from electrical conductivity measurements and the degree of humification determined by the ratio FA/HA. The inhibition of the biological activity was associated with the presence of high amounts of very mobile soluble or pseudosoluble compounds in the soil to the detriment of more condensed compounds. A high FA/HA ratio, and a low residual humin characterized the evolution of the organic matter in sodic soils. The extent of the movement of the radioactive humified compounds (soluble and pseudosoluble) was shown to increase as the soil salinity increases. The humification mechanisms in saline were then compared to those taking place in an eutrophic mull.