Simulations of Nitrate Leaching from Sugarcane Farm in Metahara, Ethiopia, Using the LEACHN Model

Abstract

Metahara is the largest sugarcane farm in Ethiopia. It produces around 120,000 tons of sugar per year. The farm has been facing some problems such as salinity and sodicity, which has been studied by different experts for several decades. However, the other universal problem of agricultural farms is nitrate leaching loss, which has never been studied in the site, owing to lack of resources and expertise. The amount of nitrate leaching from agricultural farms can be measured directly from drainage rates or estimated by using numerical models. Measurements of drainage flow can be done by using lysimeters, but normally it can be estimated from water balance calculations or from field measurements of hydraulic gradients and hydraulic conductivities. However, in reality, hydraulic conductivity is highly variable and measurements in the field can be very laborious. Moreover, predicting nitrate leaching losses by using numerical models from such data- poor study area is also another problem. Nevertheless, groundwater nitrate concentration of the farm is measured by using the UV screening and distillation methods. Using the experimental results as an input for the model calibration, the amount of nitrate leaching from the farm is predicted for a 47 years of simulation period using the LEACHN model. In this case, both the measured and predicted values of nitrate leaching losses show that there is no nitrate problem in the site. However, even though the likelihood of detecting nitrate contamination in the study area is low, potential anthropogenic nitrogen sources must be carefully managed, for it is better to be safe than regretful.