Abstract
Soil erosion is amongst the primary environmental concerns and strongly affects the Ecuadorian Andes. To lower the impact of subsistence farming on marginal land, ”Slowforming terraces” have been advertised as a conservation strategy for decades, but their adoption and maintenance rates are low. Productivity declines have been observed in these terraces in the short-term, yet there is no information about their long-term development. Aside from erosion, insufficient sanitation is another alarming issue and ”Ecological Sanitation” (EcoSan) can provide a safe, affordable and environmentally friendly solution while at the same time contributing to soil conservation. However socio-cultural and psychological implications limit its acceptance. The use of human manure (humanure) for the restoration of degraded soils (instead of conservation), which contribute considerably to erosion, could be an ecologically sound alternative and potentially facilitate the acceptability of EcoSan. Regarding slow-forming terraces, this study examined (i) if the short-term disadvantages persist in the long-term and (ii) how common land use change (to pasture) affects their development. Topographic measurements and analysis of soil and plant characteristics have been undertaken in the same terraces in Jima, Ecuador, that have been used for a short-term investigation (about 17 years ago). The previous high spatial heterogeneity of soil properties and crop performance, caused by translocation of topsoil, disappeared almost entirely in the long-term. Land use change to pasture after cultivation for ≈ 5 years resulted in a similar development as continuously cultivated terraces (slope reduction of 50-60 %). These findings could contribute to improved acceptance. Regarding the use of humanure in restoration, the study assessed the effect on (i) erodibility, (ii) biomass production and (iii) vegetative community composition on 21 plots on an eroded area in the Azuay province, Ecuador. Humanure- (TH) and humanure-biochar urine-treatment (THBU) have been tested against control using a randomised complete block design. One year after treatment application TH showed no effect on erodibility, but a significant increase of 70% in biomass and affected community composition by favouring legume growth (4.5 -fold increase in biomass compared to control). THBU showed a decrease in sediments (<2mm) in the runoff and an increase in legumes (2.4 -fold), but no increase in total biomass, due to a reduction in grasses. These results suggest that humanure could be used effectively in soil restoration. Slow-forming terraces and the use of humanure for restoration of degraded land can thus form part of an effective strategy to accomplish soil conservation. This strategy should be conceived as an integrated approach and consider different sources of land degradation, their causes, interactions and reduction potential. Revision of underlying assumptions and unintended effects as well as consideration of socio-cultural and psychological factors should complete this strategy.