SOIL AND WATER CONSERVATION BY CONTOUR HEDGING IN THE HUMID TROPICS OF PERU

A study was conducted for over 6 years (October 1987-December 1993) in the humid tropics of Peru at Yurimaguas (annual rainfall 2200 mm) on a sloping (15-20%) Typic Paleudult to evaluate the soil and water cons ervation potential of contour hedgerows of Inga edulis (locally known as guaba). The experiment involved two treatments: (a) sole crops of r ice and cowpea in annual rotation and (b) intercropping of annual crop s between inga contour hedgerows 4 m apart, replicated three times in a randomised block design. Non-replicated plots of bare-fallow and sec ondary forest were also monitored for soil loss and runoff. Contour he dgerow intercropping conserved, on average annually, 287 mm water and 73 t ha(-1) soil, which represented 83% and 93% respectively of the am ounts that were lost from sole cropping; it maintained soil nutrients at a much higher level and improved soil physical conditions compared with sole cropping of annuals. The significant soil and water conserva tion achieved by hedgerows, however, did not translate into a striking crop yield increase during the 5 year monitoring period; only the yie lds of three out of 15 crops in the last 2 years were significantly hi gher in hedgerow intercropping than in sole cropping. The lack of resp onse was partly due to the fact that 22% of the land area was lost to the hedgerows and partly that a longer time span may be required to re alise the benefits of soil conservation. However, contour hedgerow int ercropping is recommended for moderate sloping lands of the humid trop ics in Peru, considering the long-term conservation of land resource a nd the potential for continuous cropping with minimal inputs.