Central Vietnam is a region that suffers from hostile climate (drought, flooding) and sandy soils that are low in fertility. As a consequence of these conditions, the regions is less favored for agricultural development than the Mekong River Delta. Soils fertility is a function of the quantity and quality of organic matter transformed by soil organisms, like earthworms, which are commonly viewed as bio-indicators of soils fertility.
A new study, published in Tropical Conservation Science, examined the relationship between the characteristics of soil and earthworms. It found that certain families of earthworms were more likely to be found in specific soil types. The highest earthworm diversity was documented in soils growing crops like manioc and sweat potatoes rather than rice.
Zirbes, L., Collin, C., Dufey, J., Khanh Tu, P., Duyet, N., Francis, F., Lebailly, P., Haubruge, E. et Brostaux Y. 2009. Mise en relation de la diversité des vers de terre et des caractéristiques du sol de Thua Thien Hue (Centre Vietnam). Tropical Conservation Science Vol. 2 (3):282-298.