Effects of antecedent soil moisture on runoff and soil erosion in alley cropping systems

Alley cropping systems may prevent soil and water erosion. The objective of this paper was to assess the effects of antecedent soil moisture on runoff and soil loss in alley cropping systems. Five land use treatments with three replications were included in this study. The treatments were mono peanut cropping (P), younger trees (T1), older trees (T2), peanut (Arachis hypogaea) intercropped with younger trees (T1P), and peanut intercropped with older trees (T2P). The trees used were deciduous Choerospondias axillaris. Runoff and soil loss from the experimental plots were monitored and related to rainfall and antecedent soil water potential. Results showed that T1 and T2 produced the highest runoff and lowest soil loss while P produced the greatest soil loss. Soil loss was 25.3% less in T1P and 32.0% in T2P than in P. Runoff was 62.6% less in T1P than in T1 and 56.1% less in T2P than in T2. Regardless of land use, soil loss was more closely correlated to runoff than to rainfall (R > 0.95 versus R < 0.40). Runoff and soil loss varied with season and antecedent soil moisture. The largest amounts of runoff and soil loss were recorded in the soil water surplus phase (rainy season). In spite of less rainfall in the soil water deficit phase, soil loss was greater than that in the soil water recovery phase. The runoff coefficient was exponentially correlated to the inverse of antecedent soil water potential in the rainy season, while the runoff coefficient was negatively and linearly correlated to antecedent soil water potential in the dry season. These results suggest that saturation excess runoff may be dominant in the rainy season and infiltration excess runoff may become dominant in the dry season.