Crop yields in
rainfed systems may decrease 40–80% during drier El
Nin˜o years (DaMatta et al., 2003; Salinas-Zavala et al.,
2002). In 1997–1998, when Chiapas experienced a dry,
El Nin˜o summer, agricultural production dropped
dramatically (Magana Rueda and Mendez Perez,
2002) leading to severe food shortages. The loss of
food production during these El Nin˜o years points to the
need for agricultural systems that protect against water
loss, especially during these extended dry seasons.