Natural Vegetative Strips In Degraded Calcareous Soil Environments: Successful Stabilization Of Steep Slopes In The Central Philippines

Marco  Stark,; Julito  Itumay,

Natural Vegetative Strips In Degraded Calcareous Soil Environments: Successful Stabilization Of Steep Slopes In The Central Philippines

Abstract:

While a good understanding exists of the effects of low-cost natural vegetative contour strips (NVS) and their contribution to enhanced land productivity in deep acidic soil environments, little is known about the benefits and constraints of this soil conservation technology under severely degraded calcareous soil conditions. Shallow calcareous soils are common in Central Philippines covering more than half of the total land area of the Visayan islands. Based on the results from the documentation of the traditional use of NVS in Bohol, the World Agroforestry Centre (ICRAF) has conducted on-farm trials since May 2001 to assess the local practice in more detail. Observations made over a period of 1 1/2 years since NVS establishment, confirmed that the vegetative strips are highly effective in collecting eroded sediments in soils derived from either limestone or marl. The accumulation of the eroded in and above the NVS resulted in the formation of terraces that made landcultivation easier and further reduced soil erosion. Consequently, the maize yield on lower terrace zones improved right from the 1st cropping season after NVS establishment, presumably because of the deeper soil and higher water retention capacity resulting from the accumulation of sediment behind the NVS. Improved maize growth compensated for the 20% loss of crop area to the vegetative strips. Together with the findings derived from research on deep acidic soils in Northern Mindanao, findings of this research support the exploration of the NVS technology from ICRAF's research sites to the major soil environments of the Philippine uplands.

References:

CELESTINO, A.F. AND F.P. ELLIOT. 1986. Hillyland farming systems in the Philippines: an assessment. Farming Systems and Soil Resources Institute, University of the Philippines, Los Baños, Philippines.
FUJISAKA, S. AND P.A. CENAS. 1993. Contour hedgerow technology in the Philippines: not yet sustainable. Indigenous Knowledge & Development Monitor 1 (1): 14-16.
GARRITY, D.P., D.M. KUMMER AND E.S. GUIANG 1993. The Philippines. In: Sustainable agriculture and the environment in the humid tropics (National Research Council). National Academy Press, Washington, D.C., pp. 549-624.
GARRITY, D.P. 1996. Tree-soil-crop interactions on slopes. In: Tree-crop interactions. A physiological approach (C.K. Ong and P. Huxley). CAB International, Wallingford, UK, pp. 299-318.
IIRR, DENR AND FORD FOUNDATION. 1992. Agroforestry Technology Information Kit (ATIK). Silang, Philippines: IIRR (International Institute of Rural Reconstruction), DENR (Department of Environment and Natural Resources) and Ford Foundation.
MERCADO, A.R. Jr., D.P. GARRITY, N. SANCHEZ AND L. LAPUT. 1999. Appropriate spacing of natural vegetative filter strips in upland conservation farming systems. Paper presented during the 15th Annual Scientific Congress of the Federation of Crop Science Societies in the Philippines on 10-15 April 1999, General Santos City, Philippines.
PURC. 1980. Soil erosion control measures for the uplands. Philippine Upland Resource Centre (PURC), Manila, Philippines.
STARK, M. 2000. Soil management strategies to sustain continuous crop production between vegetative contour strips on humid tropical hillsides: Technology development and dissemination based on farmers' adaptive field experimentation in the Philippines. ICRAF Southeast Asia Regional Research Programme. Bogor, Indonesia.
TUNG, L. AND D.L. ALCOBER. 1991. Natural grass strips are preferred. ILEIA Newsletter 7 (1&2): 27-28.
THAPA, B. 1997. Contour ridge tillage and natural grass barrier strip effects on soil erosion, soil fertility, and corn production on sloping Oxisols in the humid tropics. PhD dissertation. North Carolina State University, Raleigh, USA.