The lack of available phosphorus in Burkina Faso’s tropical ferruginous soils led us to produce an organic fertiliser called «Neyma compost» using local materials. The Fischer block system of 4 treatments with 3 replicates was implemented during the 2023 growing season at the Kamboinsé Centre for Environmental, Agricultural and Training Research to evaluate the performance of compost on the availability of assimilable phosphorus in cowpea crops. The treatments were the control (T0); 2 t/ha of Neyma compost incorporated during ploughing (T1); 2 t/ha of Neyma compost applied to the seed holes 15 days after sowing (T2) and 1 t/ha of Neyma compost incorporated during ploughing followed by 1 t/ha applied to the seed holes 15 days after sowing (T3). The objectives of the study were to evaluate the rate of available phosphorus in soils according to application methods, determine the most efficient application method in terms of available phosphorus content, and determine the soil properties that control phosphorus availability. The results showed that the assimilable phosphorus content was improved by approximately 21% overall through the application of Neyma compost, with the assimilable phosphorus content varying from 3.5 ppm to 6.1 ppm under the different compost application methodsThe greatest improvement in assimilable phosphorus content (56%) was achieved with the T1 application method. The availability of phosphorus varied according to the physical and chemical parameters of the soil. The methods of application and doses of Neyma compost were the main factors influencing the availability of phosphorus in the soil. Neyma compost may be a promising alternative for sustainable soil management in Burkina Faso by small-scale producers.

Soil fauna significantly influences soil properties. Organic and inorganic fertilization in agriculture, including the amendment with phosphate rock, may affect its presence in soils. This study evaluated the effect of calcined phosphate rock associated with organic matter on the abundance and diversity of soil macrofauna in semi-arid areas of Burkina Faso. Nine treatments were replicated four times each and applied in a complete randomized block design in sorghum and cowpea fields. These treatments were: absolute control (Control) without fertilizer, control with organic matter only (OM), Burkina Phosphate Rock (BPR) with 23 P ha-1, calcined phosphate rock (CPR with 23 P kg ha-1), Triple super phosphate (TSP), complex fertilizer (NPK), CPR ½ +TSP ½, CPR ¾ +TSP ¼, CPR ¼ +TSP ¾ Urea provided N, and KCl supplied K in the BPR and TSP treatments. P was supplied by Triple Super Phosphate (TSP) in the TSP treatment. K and P were supplied by the complex fertilizer NPK in NPK treatment. Results showed that BPR and CPR did not significantly (P˃0.05) improve soil fauna abundance and diversity after two years. Four orders, Coleoptera, Haplotaxida, Hymenoptera, and Isoptera, were largely dominant (more than 50 %) in all treatments, crops, and years. The population diversity of soil macrofauna rises from 0.98 (2021) to 1.49 (2022) in the sorghum field and from 1.16 (2021) to 1.63 (2022) in the cowpea field. Soil macrofauna numbers rise from 24.64 ind/m2 (2021) to 39.59 Ind/m2 (2022) in the cowpea field. Our findings suggest that cultivated soil fauna can be managed more appropriately with fertilizers from phosphate rock by combining organic matter application and cereal-legume associations.

Due to its multiple functions, soil macrofauna plays a major role in the functioning of agroecosystems. However, its abundance and diversity can be influenced by various human activities such as agricultural practices. This study, initiated on ferric lixisols in the Sudano-Sahelian zone of Burkina Faso, aims to evaluate the effects of four agroecological practices on soil macrofauna. So, forty farmers' plots were sampled, based on a typology of cropping practices, associating water and soil conservation techniques (stone barriers) with generalized or localized (zaï) application of organic matter. Generalized input of organic matter is combined with mineral fertilization by microdose or not and localized input is combined with crop rotation or not. Macrofauna was collected, sixty days after sowing, using the monolith method. Three (3) monoliths were collected per plot. Manually sorted macrofauna was identified in the laboratory. The results allowed that thirty-six (36) families were identified whom the best abundant are: Termitidae (35 %), Formicidae (18 %) and Iulidae (7.7 %). Functionally, saprophages constitute 61.4 % of the population against 16.6 % of phytophagous, 13.9% of predators and 7.6 % of geophagous. Agroecological practices with uniform application of organic manure yielded the highest number of invertebrates (62.2 %) compared to localized application (37.8 %). The use of organic manure as an agroecological practice allows for better colonization of the soil by living organisms, provided that it is evenly distributed throughout the plot.