Soil Organic Carbon Storage, <i>N</i> Stock and Base Cations of Shade Coffee, Khat and Sugarcane for Andisols in South Ethiopia

Abstract

In the Wondo Genet, Ethiopia, the common agricultural land uses include maize, shade coffee, khat and sugarcane. The objective of this study was to examine the impact of perennial land uses on soil organic carbon ( SOC ), soil N and base cations. Four sites having maize and one or two of perennial land uses and with similar site characteristics were identified for this study. Soils (0 - 30 cm) were sampled at corners of a plot (20 × 20 m 2 ) placed in each land use at each site. Results indicated that the SOC storage of the shade coffee plantations were 86% and 125% higher compared with adjacent maize land uses with the absolute differences being 50.7 and 54.4 Mg &#183 ha -1 , respectively. The soil N stock was 109% and 126% higher for the shade coffee than the maize land use while the absolute differences were 5.7 and 4.7 Mg &#183 ha -1 for the same sites. Among perennials, the higher SOC storage in the shade coffee is attributable to the increased litter input and reduced soil disturbance in the system. While the higher soil N in the shade coffee was attributed to reduction of leaching, N uplift, and the increased litter quality and input. The high relative increase in shade coffee in SOC and soil N at Finance site was ascribed to the finer soil texture and low SOC and soil N at the compared adjacent maize farm. Although not significant, the relative increase in SOC (34%) and soil N (43%) in the sugarcane at the Finance as well as the relative increase in SOC (7%) and soil N (9%) in khat at Gotu as compared to Chaffee site was attributed to mainly the management differences. The shade coffee has the greatest potential for SOC storage and for increasing N stock, while khat and sugarcane have the least potential.