Construcción de indicadores agrarios para medir la sostenibilidad de la producción de cacao en el Oro, Ecuador

Abstract

The aim of this Ph. D. thesis was to assess various indicators to measure the sustainability of fields owned by some producers of cacao in the province of El Oro-Ecuador taken into account economic, social and environmental dimensions. The population studied consisted of fields cultivated with CCN51 (n=49) and cacao National (n=24), where, first a survey has been performed to obtain economic and social indicators. The environmental indicators were obtained from 30 soil samples, selected from the whole population studied, and these samples have been collected in the first 30 cm. Subsequently, the soil physicochemical properties were analysed for obtaining an index of soil (ISQ). The studied soils belonged to the Alfisols, Inceptisols and Entisols orders. Principal component analysis has been applied using an adimensional procedure, after normalisation of the selected indicators between 0 and 1. To verify the effects of agronomical management on organic matter (MO) content analysis stable isotopes13C and 15N have been performed and the degrees of aromaticity versus aliphaticity have been characterised by means of infrared spectroscopy of infrared (IR), in soil and cacao litter. The main results from the economic point of view were the production of the cacao type CCN51 (2337.63 Kg ha-1) and the resulting earned income ($1204) that were higher than those corresponding to the cacao National (476.92 Kg ha-1 versus $919.68). Considering the social aspect, 32.88% of the field owners were of more than 60 years of age and 53% had primary education. The soil properties of showed predominance of silt and clay contents, with mean values of soil organic matter (MO) lower than 3% and mean pH=6,9; no statistical differences were appreciated between soil order or cacao type. The cation exchange capacity (CEC), sum of bases (SB), pH, organic C, available phosphorus (P) sand, silt and clay contents were the properties selected as Indicators of Soil Quality (ISQ). The averages of 13C (-25.11‰) and 15N (8.8‰) corresponded to thresholds of moderate application of synthetic fertilizers. The soil IR spectra indicated aromaticity in the region 1650 cm-1, whereas for the litter, the features observed in the region around 2950 cm-1 indicated typical peculiarities of the aliphatic groups. In average the value of normalised indicators was 0.52, so that the studied fields can be ranked in the class of week sustainability.