Conversion of home garden agroforestry to crop fields reduced soil carbon and nitrogen stocks in Southern Ethiopia

Abstract

The main objective of this study was to determine how the conversions of home gardens to mono-crop fields affect soil organic carbon (SOC) and total nitrogen (TN) stocks. The study compared SOC and soil TN stocks in 7 paired sites of home gardens and converted mono-crop fields (khat and sugar cane; cultivated for 1–20 years after conversion) in Wondo Genet, Southern Ethiopia. Except two recently converted mono-crop fields (1 and 4 years after conversion), most of converted mono-crop fields had significantly lower contents of SOC (18.3–47.1 %) and soil TN (14.9–45 %) compared to home gardens. Converted mono-crop fields over 10–20 years old showed significantly lower SOC stocks (18.2–30.2 %) and soil TN stocks (16.7–28.7 %) compared to home gardens. There was no significant relationship between the periods after conversion and the rate of decrease of SOC and TN stocks in the mono-crop fields. Study results show that conversion of home gardens to mono-crop fields decreases SOC and TN stocks. Further studies are needed to identify the major mechanisms causing the decrease and quantify the change of SOC and TN in different environment and climate conditions.