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 conservation potential of contour hedgerows of Inga edulis (locally known as guaba). The experiment involved two treatments: (a) sole crops of rice and cowpea in annual rotation and (b) intercropping of annual crops between inga contour hedgerows 4 m apart, replicated three times in a randomised block design. Non-replicated plots of bare-fallow and secondary forest were also monitored for soil loss and runoff. Contour hedgerow intercropping conserved, on average annually, 287 mm water and 73 t ha-1 soil, which represented 83% and 93% respectively of the amounts 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 conservation achieved by hedgerows, however, did not translate into a striking crop yield increase during the 5 year monitoring period; only the yields of three out of 15 crops in the last 2 years were significantly higher in hedgerow intercropping than in sole cropping. The lack of response 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 realise the benefits of soil conservation. However, contour hedgerow intercropping is recommended for moderate sloping lands of the humid tropics in Peru, considering the long-term conservation of land resource and the potential for continuous cropping with minimal inputs.