Assessment of soil and water conservation methods applied to the cultivated steeplands of southern Honduras

Abstract

Erosion associated with burning and cultivating steepland fields is a common problem throughout Central America. Quantifying the magnitude of effectiveness of soil and water conservation practices such as vetiver grass hedgerows and mulching and the impact associated with the traditional practice of burning fields prior to planting were evaluated using a paired runoff catchment study design. Runoff, soil, total nitrogen, and total phosphorus loss observations from three steepland field catchments were measured for storm event(s) over a three-year period (1993-1995). The 0.2 ha field catchments with 60% slopes were monitored in the community of Los Espabeles near Choluteca, Honduras. During the calibration period (1993), all three catchments were managed the same with mulch only. During the treatment period (1994-1995), one catchment combined mulch management with contour vetiver grass hedgerows, one catchment was burned prior to planting, and one catchment served as the control with mulch only. Combining vetiver grass hedgerows with mulching significantly (p<O.10) reduced runoff as compared with mulch only. The traditional practice of burning fields prior to planting significantly (p<O.10) increased runoff as compared with mulch only. The vetiver grass hedgerows reduced soil loss more than mulching alone. Not only did vetiver grass form a barrier to runoff and soil loss, it helped protect the integrity of the steepland field against major sloughing events which occurred on the other two fields without vetiver grass. The slash & bum practice significantly (p<O.10) increased soil loss as compared with mulching. The Universal Soil Loss Equation (USLE) and Revised Universal Soil Loss Equation (RUSLE) models were applied to cultivated steepland fields in Los Espabeles, Honduras. The predicted annual soil losses from the two models were then compared to the observed average annual soil losses measured at the same location for various size plots. In general, both models tended to over predict. However, annual soil loss predictions by RUSLE were fairly close to the observed annual soil losses. USLE predicted annual soil losses 9 times higher than RUSLE. Both USLE and RUSLE tend to over estimate on steep slopes because they are based on soil losses from gentle to rolling slopes under low to moderate rainfall energies.