Soil Depth Effects on Seedling Emergence and Persistence of Calopogonium mucunoides in Central Western Côte d’Ivoire

Calopogonium mucunoides is a tropical cover crop reported as a major weed of food crops in the Central Western Côte d'Ivoire. In order to use it effectively as cover crop while preventing its proliferation as a weed of crops, a study was conducted on the depth of emergence of its seedlings and the persistence of its seeds in the soil. The experimental design used to observe the influence of seed sowing depth on seedling emergence and seed persistence in the soil is a completely randomized design. The study was carried out in the department of Issia, from March to May 2013 for the experiment of seedling emergence depths and from April 2013 to April 2014 for the study of seed persistence in the soil. To determine the seedling emergence depth, four replicates of 100 Calopogonium mucunoides seeds were sown at different depths in nursery bags filled with sandy-agilous soil. To study seed persistence, 100 seeds of this weed were also placed in finely perforated nylon bags and buried at different soil depths for one year. The results of the study showed that the highest rate of Calopogonium mucunoides seedling emergence were observed along the first five centimeters from the soil surface and the lowest at 10 cm. In terms of seed persistence, it was noted that more than 70% of Calopogonium mucunoides seeds remained viable in the soil after one year of burial. These results suggest that in plantations infested with Calopogonium mucunoides, deep plowing will prevent seedlings of this species from emerging. Furthermore, because the seeds of this species are persistent in the soil, already emerged seedlings should be removed before they reach the fruiting stage to avoid increasing its seed bank in the soil.