Effects of cultivation time on soil physical, chemical properties, soil organic carbon, total nitrogen stocks and dioxide carbon emission in Southeast of Chad
This study aimed to examine the effects of agricultural activities on soil physico-chemical, SOC, TN stocks and CO2 emissions as a function of cultivation duration. The study was carried out in southeastern Chad, focusing on three localities near the city of Am-Timan: Darasna (North-East), Madina (South) and Goz-Mabile (West). These sites have been intensively cultivated for flood recession sorghum production under glyphosate use for 25 35 and 50 years, respectively. Six soil profiles were collected and a total of 144 samples were obrained-36 per site. Soil samples were collected randomly from each plot at 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-50 cm and 50-60 cm in triplicate per experimental unit. The results indicated that soil pH in the study area was slightly alkaline and influenced by cultivation duration, with the highest pH observed after 25 years of cultivation. Additionally, soil bulk density and texture were affected by the duration of agricultural practices. The highest bulk density was recorded after 25 years of cultivation, while lower bulk densities were observed after 35 and 50 years of farming practices, highlighting the impact of cultivation time on soil compaction. A decline in SOC and TN stocks was evident with more than 25 years of cultivation, along with an increase in CO2 emissions, particularly in the topsoil (0-20 cm) and subsurface (20-40 cm). Reducing cultivation duration may enhance soil fertility by improving soil physicochemical, as well as soil organic matter, ultimately contributing to increase crop yields and climate change mitigation.
Keywords: Soil organic carbon, Total nitrogen, Carbon dioxide emission, Agricultural land, Chad, Vertisol
