Global Journal of Science Frontier Research, D: Agriculture and Veterinary, Volume 21 Issue 7

IV. D iscussion a) Effects of mulching and legumes on soil moisture Mulching improved soil moisture status compared to bare soil at the 21 st DAP of maize. Mulching protects the soil from direct sunlight, which reduces water loss by evaporation. These results are similar to results from previous studies (Bougoum, 2012; Kohio, 2015; Doumbia, 2016). However, by the 35 th DAP, mulching did not have a significant effect on soil moisture. We noticed a progressive loss of mulch cover due to its decomposition. The straw deteriorated throughout the growing season and its impact on soil moisture diminished. Concerning the effect of legumes on soil moisture, the results revealed that legumes tended to increase soil moisture compared to soil without cover crops at the 49 th DAP of maize. Legumes as cover crops protect the soil from direct sunlight, thereby reducing evaporation from the soil surface. Balboné (2013) found that they increased soil moisture levels when legumes were combined as cover crops. In addition, Coulibaly (2012) reported that biomass production of legumes protects the soil, thereby reducing evaporation from the soil surface. Salez (1988) also pointed out that legume covers reduce the risk of erosion and improve soil moisture. Our results indicate that the effect of legumes varies with the crop species, likely by the fraction of soil cover provided by the legumes. The results confirm those by Balboné (2013), who reported that the effect of cover crops on soil moisture depended on the percent of soil covered and the stage of crop development. In our work, the impact of legumes on soil moisture status was significant at 56 DAP. During this period, cowpea and groundnut reached their maximum surface coverage, which was 99.92% and 89.91%, respectively. Mulching effects on soil moisture was more pronounced when combined with cover crops such as legumes. Legumes increase the amount of biomass covering the soil. Our results agree with those of Bougoum (2012). Similarly, Doumbia (2016) highlighted that soil moisture content increased with the amount of biomass used. b) Effects of mulching and legumes on weed growth The evolution of the weed growth rate differs from one treatment to another. A non-significant difference was detected among treatments regarding the effect of mulching on the rate of grassing. But the rate was higher on the straw plots than on the bare soil. This could be explained by a lack of straw covering the soil, which favored weed development due to moisture. Fredon (2012) indicated that in weed control with mulch, the thickness of the mulch is essential and must be adapted to the materials used. In addition to this component, localized irrigation reduces the amount of weed control by reducing the amount of water available for weeds. Since the moisture content was improved on straw soils, this encouraged weed development. Results overall showed that legumes reduced weed development at 56 th DAP of maize. These results could be explained by the ground cover of legumes smothering the weeds. In addition to this aspect, the high biomass production of legumes limits the germination and development of weeds. These results are consistent with those by Espoir et al. (2013), who indicated that when soybean ( Glycine max ) was used as a cover crop, it reduced weed development. Hien (2004) found that the effect of cowpea on weeds was most pronounced at 50 th DAP maize. Dao (2014) confirmed these results and reported that the rate of weed growth was low in the maize-cowpea association compared to a pure maize crop. However, we found that weed cover was higher in legume crops than in pure crops from the beginning of production. Mulching using legumes depends on their stage of development (Balboné, 2013). Similarly, Pamba et al. (2018) had shown that the installation of Mucuna ( Mucuna pruriens L.) limited the development of weeds such as Cynodon dactylon , Digitaria sp., and Imperata cylindrica . These authors attributed the effect of mucuna to its shading, which was detrimental to weed development. By the 44 th DAP, legumes had no significant effect on weed development. The soil moisture content increased, which would enhance weed development. Indeed, Pama et al. (2018) showed that weed control by association is essential in areas with low rainfall. When combining mulch with legumes, it generally reduced the weed cover at 56 th DAP for maize. Legumes increased the amount of biomass available on the soil surface, making it possible to cover the soil well. These results align with Bybee et al. (2018), who showed that crop association could reduce the amount of grass on land plots. Lawane et al. (2010) reported similar results by combining cowpea with cereals to control Striga ( Striga hermontica ). Effects of mulching and legumes on maize growth The most significant growth was under mulch. Mulching improves soil moisture, mineralization and increases the water available to the plants. Minengu et al. (2015) found similar results for maize plant growth on different cropping systems. Thus, for these authors, soil cover with Sytholantes guineensis associated with maize improves the cereal's growth in height and diameter. In contrast, Kouelo et al. (2017) found that mulching had no significant effect on maize crown diameter. According to Azontondé (1993), legumes protect soil and increase earthworm activity, improving soil structure. Improved soil structure allows good rooting and promotes soil colonization by the surface roots of maize plants. In intercropping system, maize makes better use of nitrogen fertilization (Mvondo, 1986). When organic manure is applied, cover crops improve the Effects of Cereal-Legume Intercropping and Mulching on Maize ( Zea Mays L.) Productivity in Dry Season using Drip Irrigation in South-Sudanian Climatic Zone of Burkina Faso c) © 2021 Global Journals 1 Global Journal of Science Frontier Research Volume XXI Issue VII Year 2021 12 ( D ) Version I